Engine stops after 20 minutes
09-10-2003, 06:48 PM
#1
Track Day
Thread Starter
Join Date: Jun 2003
Location: Austin, Texas
Posts: 21
Likes: 0
Received 0 Likes
on
0 Posts
Engine stops after 20 minutes
This is a 1983 928S. It has been immaculately maintained by my friend, Chris, who is great Porsche mechanic, in the business of engine rebuilds on many cars like Porsche, BMW. Valve job just done, water pump, new computer, all plugs and wires. 83K original miles.
Here's the problem, that Chris wants me to post.
I'm driving home, and after about 20 minutes, I notice the tach is fluctuating or bouncing, within a minute, I lose power, then the 928 stops. I crank it but it will not restart. I walk away looking for a phone. Mechanic guy comes along, pulls rotor, looks for spark (yes). He says "new rotor." Suddenly the car restarts. I drive down the road about a mile. Car stops again.
I tow it to Chris. Chris says rotor is new. Chris replaces ignition switch (since starting problems have been happening).
Two nights later, after about 20 minutes of driving, same thing happens (at Chris's shop). Thank Gawd because I am about to drive home again. He checks relays and fuses. He mentions that he has just replaced the Perma-Tune computer [?], at $400. He wonders if it can be malfunctioning.
He suspects something around the coil.
He asks me to post -- and we will check later tonight when he is with me.
I read another account of something like this in another thread, but the tach dropped, as opposed to fluctuating (bouncing).
Any ideas? We would very much appreciate it, and am in the market for 1983 928 Workshop Manuals.
THANKS!!!
Pat
Here's the problem, that Chris wants me to post.
I'm driving home, and after about 20 minutes, I notice the tach is fluctuating or bouncing, within a minute, I lose power, then the 928 stops. I crank it but it will not restart. I walk away looking for a phone. Mechanic guy comes along, pulls rotor, looks for spark (yes). He says "new rotor." Suddenly the car restarts. I drive down the road about a mile. Car stops again.
I tow it to Chris. Chris says rotor is new. Chris replaces ignition switch (since starting problems have been happening).
Two nights later, after about 20 minutes of driving, same thing happens (at Chris's shop). Thank Gawd because I am about to drive home again. He checks relays and fuses. He mentions that he has just replaced the Perma-Tune computer [?], at $400. He wonders if it can be malfunctioning.
He suspects something around the coil.
He asks me to post -- and we will check later tonight when he is with me.
I read another account of something like this in another thread, but the tach dropped, as opposed to fluctuating (bouncing).
Any ideas? We would very much appreciate it, and am in the market for 1983 928 Workshop Manuals.
THANKS!!!
Pat
09-10-2003, 10:08 PM
#3
Nordschleife Master
I've just finished playing around with my igniton system. I had a very werid rpm, and temp. dependent miss.
There is no crank sensor in an 83, US or Euro.
Both the US and Euro cars used the same ignition system, with slight diffrences to the distributer.
OK, lets get cooking. It's my belive that when fixing intermintent problems, it's best to check, and possible replace, the cheap things first, as if a cheap part will fix, you don't need to drop the big bucks.
OK, so you think your loseing spark. Are you for sure? Get, or have Chris get a spark tester, or inductive timeing light, and make sure when she dies your loseing spark. If it's not the ignition system, your going to spend and long to time and money if you do it yourself, or a whole lought of money if you have someone do it for you.
OK, lets assume your loseing spark. If Chirs is a 928 mechenic he should have he service mannual. There is a long flow chart with troubleing shooting guides. I've found that most "Porsche" mechanics can work on 911s, few "Porsche" mechanics can work in 928s.
I'm guessing if he's posting that he doesn't know what it is, eighter he doesn't have the service mannuals, or hasn't looked at them, or it defies the service mannuals.
Lets throw out some potential problems. It sounds like it just flat cuts out, like you turned the key off. Thats almost certanly not a spark plugs, spark leads, or distributer cap problem.
0. Pull the conecter for the tach. If your problem goes away, there's eighter somethign wrong with the tach, or the wireing associated. There is a plastic plug in the passangers foot well that you can pull that will kill the tack, and a few other unimportant things. Leave it pulled for the duration of the testing.
1. Bad green wire. There is a green wire about a meter long that runs from the back side of the distrubter to a plug in the engine harnes on the passangers side of the engine bay. It can cause a multitude of problems. If it looks at all cracked or frayed, replace it, becuse if it's bad or frayed, it will leave you stranded evencaly.
2. Bad connections/ grounds. There are two grounds on the frount long member, the steel peice in the front of the engine bay that the hood latches to. There's one on each side. They both need to be cleaned, expecaly if they've never been touched before. If you have a/c, the passanger's side ground is a witch w/ a capital B to get to. I belive the passangers side is the main ground for the igniton system. Youll see the grounds because they have a bunch of brown wires going to them, and IIRC, and 10mm head.
3. Bad ballast resisters, and their connections. They are located on the drivers side of the engine bay, between the radaiter and the side wall. Do NOT touch them after then key has been on for a few minuts, car running or not, as they get hot enough to blister your finger tips. (don't ask how I know.) One should ohm out to 0.6, and the other to 0.4. There should be basicly no rust on the connecters, as that doesn't help things. There are 3 wires to worry about here. One is the 12V supply comeing from the inductive discharge unit, This goes to, IIRC, the .6 resister. From there there is a jumper with an additional wire to the other resister. The othere wire should be dead normaly, no power, no ground. When you hit the starter, it should have at least 11V of power. This is to supply the coil wil a voltage boost, so you get the full spark when starting. The final wire goes to the coil.
4. Next on my list, pull the distributer cap, pull the rotor, check to see for charded look between the metal parts of the magnetic pick up, and the relucator. If there are chard marks, your rotor's insluation broke down, and is allowing high voltage current to the shaft. This is bad. You probably won't get away with replaceing the rotor, but will probably need a new magnetic pick up. It seems 928intl can't get them. My local Car Quest seems to be able to get the magentic pick up. It's about half the price of a used distributer, so it might be worth asking them. You'll also probably need a new relucator, but thats cheap, and seems to be avalible at most places.
5. A few quick voltage checks. Turn the key on, but do NOT start the engine. IIRC, terminal 1 of the coil should have between 3 and 2V on it. Terminal 15 should have 4+V. I could be getting those backward. If they do not, then you've got problems. If you got no power, there is a break in the circut between the key/inductive unit/ballast resisters/coil. If you've got too much voltage, you eighter have bad ballast resisters, which you just checked, or a bad coil, or a bad ground which you've just cleaned.
6. Wrong, or bad coil. The service mannual has spec. for the coil to ohm out at, I don't rember them. If your system is OEM, you need and OEM coil. The OEM inductive discharge unit apperently doesn't like coils that have the wrong number of windings, like "hotter" aftermarket coils do. OEM 928 coils rarely go bad, but it is possible.
8. Pull the connecter to the inductive unit. There is one connecter that should be a ground, one that should go to the tach, two that should go to the green wire, and one that should supply power. Make sure the ground is good, there is with in 1 volt on the jump start terminal for the power, the green wire connecters go to the green wire, and the tack is dead, no power, no ground. If something wrong here, you've got wireing issues, and need to deal with that.
9. OK you've got an OEM coil, good resisters, good wireing, about the only thing left is the inductive discharge unit. The inductive discharge unit is not a computer. It's basicly a electricly controled switch. It turns the small electric current spikes generated by the magentic pick up into breaks in the 12v current that supplys the coil assymbly. These breaks in current fire the coil, makeing the spark. The breaks are carefuly timed to a certain dwell. The dwell is not adjustable. It should be around 32 or 33 degrees, IIRC. If it's not, the unit needs to be replaced. All advance and retard issues are delt with by the distributer.
10. OK, you've checked everything now. You have good wireing, a good coil, good resisters, good power supply, etc. There is no real way for a backward mechenic to "test" the inductive unit. Some aftermarket units don't seem to like some of the 928's igniton componets. I think Capasative Discharge ignition units don't like the ballast resisters, but I'm not sure. I know the OEM coil won't last long with the resisters shorted out. OK, the last componet is the inductive discharge unit. You can buy a used one from one of the big three for a reasonable price.
Unless I was doing something strange, I wouldn't worry about upgradeing the 928's ignition system. It's very powerful. The 928's system will hanndle just about everything that you throw at it, excepteing freekisly rich conditons. It's far better than the old points system. The reson that the world shifted to Capasative Discharge, and multi strike units, compared to inductive discharge is plug fouling. A inductive discharge unit doesn't build up the voltage as rapaidly as a CD unit. An inductive unit only fires the plugs once. A CD unit that fires the plugs multipul times standands a much better chance of "punching" through junk that fouls plugs. A inductive discharge system is more powerful than a points system and is less sensitive to plug fouling. An 83 928 uses a well designed EFI system. The EFI system does a very good job of maintaining the A/F mixture, resulting in there basicly being no plug fouling. Racers, and supercharged cars, on the other hand use a much richer mixture, to gain more power, and have more issues with fouling.
Be very careful when dealing with the 928's igniton system, as there are multipul warnings in the service mannual that it can kill you. In fact there is a whole page, plus foot notes. Just a little common sense.
Good luck.
There is no crank sensor in an 83, US or Euro.
Both the US and Euro cars used the same ignition system, with slight diffrences to the distributer.
OK, lets get cooking. It's my belive that when fixing intermintent problems, it's best to check, and possible replace, the cheap things first, as if a cheap part will fix, you don't need to drop the big bucks.
OK, so you think your loseing spark. Are you for sure? Get, or have Chris get a spark tester, or inductive timeing light, and make sure when she dies your loseing spark. If it's not the ignition system, your going to spend and long to time and money if you do it yourself, or a whole lought of money if you have someone do it for you.
OK, lets assume your loseing spark. If Chirs is a 928 mechenic he should have he service mannual. There is a long flow chart with troubleing shooting guides. I've found that most "Porsche" mechanics can work on 911s, few "Porsche" mechanics can work in 928s.
I'm guessing if he's posting that he doesn't know what it is, eighter he doesn't have the service mannuals, or hasn't looked at them, or it defies the service mannuals.
Lets throw out some potential problems. It sounds like it just flat cuts out, like you turned the key off. Thats almost certanly not a spark plugs, spark leads, or distributer cap problem.
0. Pull the conecter for the tach. If your problem goes away, there's eighter somethign wrong with the tach, or the wireing associated. There is a plastic plug in the passangers foot well that you can pull that will kill the tack, and a few other unimportant things. Leave it pulled for the duration of the testing.
1. Bad green wire. There is a green wire about a meter long that runs from the back side of the distrubter to a plug in the engine harnes on the passangers side of the engine bay. It can cause a multitude of problems. If it looks at all cracked or frayed, replace it, becuse if it's bad or frayed, it will leave you stranded evencaly.
2. Bad connections/ grounds. There are two grounds on the frount long member, the steel peice in the front of the engine bay that the hood latches to. There's one on each side. They both need to be cleaned, expecaly if they've never been touched before. If you have a/c, the passanger's side ground is a witch w/ a capital B to get to. I belive the passangers side is the main ground for the igniton system. Youll see the grounds because they have a bunch of brown wires going to them, and IIRC, and 10mm head.
3. Bad ballast resisters, and their connections. They are located on the drivers side of the engine bay, between the radaiter and the side wall. Do NOT touch them after then key has been on for a few minuts, car running or not, as they get hot enough to blister your finger tips. (don't ask how I know.) One should ohm out to 0.6, and the other to 0.4. There should be basicly no rust on the connecters, as that doesn't help things. There are 3 wires to worry about here. One is the 12V supply comeing from the inductive discharge unit, This goes to, IIRC, the .6 resister. From there there is a jumper with an additional wire to the other resister. The othere wire should be dead normaly, no power, no ground. When you hit the starter, it should have at least 11V of power. This is to supply the coil wil a voltage boost, so you get the full spark when starting. The final wire goes to the coil.
4. Next on my list, pull the distributer cap, pull the rotor, check to see for charded look between the metal parts of the magnetic pick up, and the relucator. If there are chard marks, your rotor's insluation broke down, and is allowing high voltage current to the shaft. This is bad. You probably won't get away with replaceing the rotor, but will probably need a new magnetic pick up. It seems 928intl can't get them. My local Car Quest seems to be able to get the magentic pick up. It's about half the price of a used distributer, so it might be worth asking them. You'll also probably need a new relucator, but thats cheap, and seems to be avalible at most places.
5. A few quick voltage checks. Turn the key on, but do NOT start the engine. IIRC, terminal 1 of the coil should have between 3 and 2V on it. Terminal 15 should have 4+V. I could be getting those backward. If they do not, then you've got problems. If you got no power, there is a break in the circut between the key/inductive unit/ballast resisters/coil. If you've got too much voltage, you eighter have bad ballast resisters, which you just checked, or a bad coil, or a bad ground which you've just cleaned.
6. Wrong, or bad coil. The service mannual has spec. for the coil to ohm out at, I don't rember them. If your system is OEM, you need and OEM coil. The OEM inductive discharge unit apperently doesn't like coils that have the wrong number of windings, like "hotter" aftermarket coils do. OEM 928 coils rarely go bad, but it is possible.
8. Pull the connecter to the inductive unit. There is one connecter that should be a ground, one that should go to the tach, two that should go to the green wire, and one that should supply power. Make sure the ground is good, there is with in 1 volt on the jump start terminal for the power, the green wire connecters go to the green wire, and the tack is dead, no power, no ground. If something wrong here, you've got wireing issues, and need to deal with that.
9. OK you've got an OEM coil, good resisters, good wireing, about the only thing left is the inductive discharge unit. The inductive discharge unit is not a computer. It's basicly a electricly controled switch. It turns the small electric current spikes generated by the magentic pick up into breaks in the 12v current that supplys the coil assymbly. These breaks in current fire the coil, makeing the spark. The breaks are carefuly timed to a certain dwell. The dwell is not adjustable. It should be around 32 or 33 degrees, IIRC. If it's not, the unit needs to be replaced. All advance and retard issues are delt with by the distributer.
10. OK, you've checked everything now. You have good wireing, a good coil, good resisters, good power supply, etc. There is no real way for a backward mechenic to "test" the inductive unit. Some aftermarket units don't seem to like some of the 928's igniton componets. I think Capasative Discharge ignition units don't like the ballast resisters, but I'm not sure. I know the OEM coil won't last long with the resisters shorted out. OK, the last componet is the inductive discharge unit. You can buy a used one from one of the big three for a reasonable price.
Unless I was doing something strange, I wouldn't worry about upgradeing the 928's ignition system. It's very powerful. The 928's system will hanndle just about everything that you throw at it, excepteing freekisly rich conditons. It's far better than the old points system. The reson that the world shifted to Capasative Discharge, and multi strike units, compared to inductive discharge is plug fouling. A inductive discharge unit doesn't build up the voltage as rapaidly as a CD unit. An inductive unit only fires the plugs once. A CD unit that fires the plugs multipul times standands a much better chance of "punching" through junk that fouls plugs. A inductive discharge system is more powerful than a points system and is less sensitive to plug fouling. An 83 928 uses a well designed EFI system. The EFI system does a very good job of maintaining the A/F mixture, resulting in there basicly being no plug fouling. Racers, and supercharged cars, on the other hand use a much richer mixture, to gain more power, and have more issues with fouling.
Be very careful when dealing with the 928's igniton system, as there are multipul warnings in the service mannual that it can kill you. In fact there is a whole page, plus foot notes. Just a little common sense.
Good luck.
Last edited by ViribusUnits; 09-11-2003 at 11:12 PM.
09-10-2003, 10:27 PM
#4
Track Day
Thread Starter
Join Date: Jun 2003
Location: Austin, Texas
Posts: 21
Likes: 0
Received 0 Likes
on
0 Posts
Thanks so much for your very long and informative reply.
As you guessed, Chris's expertise in 928's is not as extended as it is in other Porsche models. We do not have the Workshop Manuals, but I am looking now.
I will pass this list on to him (some of it I recognize he has checked from watching him work), and I will post tomorrow evening his responses and/or questions.
[Chris only works in the evenings so it will be Thursday evening, Texas time, but wanted to get this response to you so you would know my appreciation.]
I spoke briefly with Chris tonight and he answered the previous person's suggestion (crank sensor), with the same answer you just gave.
Best regards!!!!
Pat:
bigbye:
As you guessed, Chris's expertise in 928's is not as extended as it is in other Porsche models. We do not have the Workshop Manuals, but I am looking now.
I will pass this list on to him (some of it I recognize he has checked from watching him work), and I will post tomorrow evening his responses and/or questions.
[Chris only works in the evenings so it will be Thursday evening, Texas time, but wanted to get this response to you so you would know my appreciation.]
I spoke briefly with Chris tonight and he answered the previous person's suggestion (crank sensor), with the same answer you just gave.
Best regards!!!!
Pat:
bigbye:
09-11-2003, 03:11 PM
#7
Nordschleife Master
The ignition switch provides power dirictly to the ignition system.
If you've got power at the inductive unit, and the coil, the ignition switch is OK. If you don't have power, here is a break in the wireinging, which can include the ignition switch.
If you've got power at the inductive unit, and the coil, the ignition switch is OK. If you don't have power, here is a break in the wireinging, which can include the ignition switch.
Trending Topics
09-11-2003, 08:52 PM
#8
Instructor
Join Date: Jun 2001
Location: Southern Maine
Posts: 109
Likes: 0
Received 0 Likes
on
0 Posts
I see you have a pre S4. The symptoms you are describing are exactly how mine acted during thrust bearing failure. Im pretty sure your engine isnt as vulnerable to this catastrophe as an S4 but, It may be worth checking the end play in the crank. I hope that it isnt the case......I almost cried with mine.
09-12-2003, 02:15 PM
#9
Track Day
Thread Starter
Join Date: Jun 2003
Location: Austin, Texas
Posts: 21
Likes: 0
Received 0 Likes
on
0 Posts
Thrust bearing failure
Hi Brendan:
I will be meeting with Chris tonight (where the 928 sits). And sharing with him everybody's generous responses.
I am shuddering to think what thrust bearing failure might possibly mean, and how it could bring you to almost cry ... but Chris will explain it to me I am sure.
Chris thinks that every time I talk or think of selling the 928, it breaks down, but he is emotional about it having rebuilt its engine, he is attached to it. It is such a fine ride, and has so much natural spirit and character.
I will let you all know when we get to the bottom of it .
Regards,
Pat
I will be meeting with Chris tonight (where the 928 sits). And sharing with him everybody's generous responses.
I am shuddering to think what thrust bearing failure might possibly mean, and how it could bring you to almost cry ... but Chris will explain it to me I am sure.
Chris thinks that every time I talk or think of selling the 928, it breaks down, but he is emotional about it having rebuilt its engine, he is attached to it. It is such a fine ride, and has so much natural spirit and character.
I will let you all know when we get to the bottom of it .
Regards,
Pat
09-13-2003, 01:00 AM
#10
Track Day
Thread Starter
Join Date: Jun 2003
Location: Austin, Texas
Posts: 21
Likes: 0
Received 0 Likes
on
0 Posts
Chris is here now
I'm here with Chris now, and appreciate everybody's responses. Here's the technical side of the 928 stopping after 20 minutes.
We noticed that after the car is fully warmed up after 25 minutes or so, when idling, the tachometer would fluctuate as the engine experienced slight misses and the engine stayed running.
We came back home and opened the hood at night to check for spark plugs wires arc-ing, found none of this but at that time while the hood was still up, the engine quit running as if someone turned the ignition key off but the key was still on the ignition position.
Just about to close the hood and we heard the fuel pump relay energize the fuel injectors. We then went inside the car, engine not running, the ignition key still on the ignition position and felt the fuel pump relay contacts opening and closing simultaneously as the tachometer fluctuated.
This process was very defined, when the tach pulsed, is exactly when the fuel pump relay would open and close. That leads us to believe that the tach is receiving a pulse when it shouldn't (cuz the engine's not running), it's also sending a pulse to the fuel pump relay and energizing it.
Therefore our question is at this point, why is the tach receiving a pulse (or the relay) or what is the source for this pulse since the engine is not running?
Side note: remember this is a 1983 which has a separate ignition module from the fuel injection box.
Here are some things that Chris thought of already:
1. pickup coil inside distributor
2. ignition box (which is new)
3. fuel pump relay (diode reversing)
4. fuel injection computer
We noticed that after the car is fully warmed up after 25 minutes or so, when idling, the tachometer would fluctuate as the engine experienced slight misses and the engine stayed running.
We came back home and opened the hood at night to check for spark plugs wires arc-ing, found none of this but at that time while the hood was still up, the engine quit running as if someone turned the ignition key off but the key was still on the ignition position.
Just about to close the hood and we heard the fuel pump relay energize the fuel injectors. We then went inside the car, engine not running, the ignition key still on the ignition position and felt the fuel pump relay contacts opening and closing simultaneously as the tachometer fluctuated.
This process was very defined, when the tach pulsed, is exactly when the fuel pump relay would open and close. That leads us to believe that the tach is receiving a pulse when it shouldn't (cuz the engine's not running), it's also sending a pulse to the fuel pump relay and energizing it.
Therefore our question is at this point, why is the tach receiving a pulse (or the relay) or what is the source for this pulse since the engine is not running?
Side note: remember this is a 1983 which has a separate ignition module from the fuel injection box.
Here are some things that Chris thought of already:
1. pickup coil inside distributor
2. ignition box (which is new)
3. fuel pump relay (diode reversing)
4. fuel injection computer
09-13-2003, 05:02 AM
#11
Has the fuel pump relay been jumped?
Check archives for description if you are unfamiliar with the jumper procedure. If jumped the relay has been by- passed(jumped) and your fuel pump has been working full time, all of the time once your ignition switch hits position #1 or more. If this has been the case a fair assumption would be that the pump is overheating/worn out. If it hasn't been jumped - you should see a jumper wire if it has been jumped - you might have a crossed wire in the fuse panel area.
Break out the multi-meter and check the fuel pump for a power supply issue at the pump connectors. Looking for continuous -non- interrupted- power which means it's jumped.
I'm not sure which MY's have an in tank as well as external pump but posters in the past have indicated when the tank pump goes the external pump works much harder, get's noisy, and eventually fails.
I'm definitely not an expert on the ignition/ECU/FCU circutry but I gather that the tach signal generates an input to the ECU/FCU to meter(mapped)
fuel flow requirements for a given engine speed.
Perhaps, you'll have to ask the guru's if there could be a tach amp that is overheating and causing intermmittent failure as heat does do strange things to the electricals and they sometimes don't fail completely.
Along these same lines there were quite a number of coil failures a year or so back, they would work ok then overheat and fail. After cool down they would work fine until heat reared it's ugly head. The symptoms ran from intermittent missing -particularly at high speeds- to total engine cut out, or non-start.
I am unsure of the connection between coil(s) and Tach signal, perhaps a Guru will jump in here...please!
I agree with checking grounds as well as cleaning/replacing the green wire and its connectors.
I believe you have only the external fuel pump on an 83' MY you might check to see if the check ball is stuck and allowing drain back, and ask Chris if he changed the fuel filter it could be restricted to the point that the pump doesn't have enough gas to feed the injectors.
You can pull the check valve-ball- and clean the shellac off of it or replace ($10.00).
Other stuff:
Which I mention because of relationship between fuel/air inputs/outputs and the Brain
1. Impulse sender -used- $30.00.
2. Thermo - time switch - $55.00.
3. Aux. air valve - used- $50.00.
4. Pressure regulator - $58.00.
5. Fuel damper - $80.00.
6. The Brain -contact John Speake.
7. Airflow meter -used- $100.00 you can generally clean these puppy's up yourself.
Odd stuff. Stuck cold start injector, Bad temp. sender.
Pull a couple of plugs and check condition/color.
Check archives for description if you are unfamiliar with the jumper procedure. If jumped the relay has been by- passed(jumped) and your fuel pump has been working full time, all of the time once your ignition switch hits position #1 or more. If this has been the case a fair assumption would be that the pump is overheating/worn out. If it hasn't been jumped - you should see a jumper wire if it has been jumped - you might have a crossed wire in the fuse panel area.
Break out the multi-meter and check the fuel pump for a power supply issue at the pump connectors. Looking for continuous -non- interrupted- power which means it's jumped.
I'm not sure which MY's have an in tank as well as external pump but posters in the past have indicated when the tank pump goes the external pump works much harder, get's noisy, and eventually fails.
I'm definitely not an expert on the ignition/ECU/FCU circutry but I gather that the tach signal generates an input to the ECU/FCU to meter(mapped)
fuel flow requirements for a given engine speed.
Perhaps, you'll have to ask the guru's if there could be a tach amp that is overheating and causing intermmittent failure as heat does do strange things to the electricals and they sometimes don't fail completely.
Along these same lines there were quite a number of coil failures a year or so back, they would work ok then overheat and fail. After cool down they would work fine until heat reared it's ugly head. The symptoms ran from intermittent missing -particularly at high speeds- to total engine cut out, or non-start.
I am unsure of the connection between coil(s) and Tach signal, perhaps a Guru will jump in here...please!
I agree with checking grounds as well as cleaning/replacing the green wire and its connectors.
I believe you have only the external fuel pump on an 83' MY you might check to see if the check ball is stuck and allowing drain back, and ask Chris if he changed the fuel filter it could be restricted to the point that the pump doesn't have enough gas to feed the injectors.
You can pull the check valve-ball- and clean the shellac off of it or replace ($10.00).
Other stuff:
Which I mention because of relationship between fuel/air inputs/outputs and the Brain
1. Impulse sender -used- $30.00.
2. Thermo - time switch - $55.00.
3. Aux. air valve - used- $50.00.
4. Pressure regulator - $58.00.
5. Fuel damper - $80.00.
6. The Brain -contact John Speake.
7. Airflow meter -used- $100.00 you can generally clean these puppy's up yourself.
Odd stuff. Stuck cold start injector, Bad temp. sender.
Pull a couple of plugs and check condition/color.
09-13-2003, 11:31 AM
#12
Pat,
Check the O plug at the bottom of the fuses panel for bad/corroded connections. This appears to be the common connection for the coil, relay, and tach (via the ignition module).
Dennis
Check the O plug at the bottom of the fuses panel for bad/corroded connections. This appears to be the common connection for the coil, relay, and tach (via the ignition module).
Dennis
09-13-2003, 01:33 PM
#13
Dennis,
'O" plug?
Do I have one?
If not, I want one!
Something new and different to go wrong...Oh Boy!
Was going to cap you on College Football since I'm a displaced Pennsylvanian ... . Of course, life dealt me yet another viscious body blow.
Can you believe it?
Boston College flogged Penn State within a a hairsbredth of being brought up on criminal intent to rape, pillage, and plunder, along with conspiracy to humilate -a federal sports crime when National Broadcast rules apply.
Jesus! It was a home game and homecoming no less!
Oh the shame... worse than being caught in a unwashed 928.
'O" plug?
Do I have one?
If not, I want one!
Something new and different to go wrong...Oh Boy!
Was going to cap you on College Football since I'm a displaced Pennsylvanian ... . Of course, life dealt me yet another viscious body blow.
Can you believe it?
Boston College flogged Penn State within a a hairsbredth of being brought up on criminal intent to rape, pillage, and plunder, along with conspiracy to humilate -a federal sports crime when National Broadcast rules apply.
Jesus! It was a home game and homecoming no less!
Oh the shame... worse than being caught in a unwashed 928.
09-13-2003, 04:51 PM
#14
Nordschleife Master
OK, you've just opened a whole new can of worms.
The 82-83 928 has something like 2 relays you need to worry about. There's the AFC relay, and the fuel pump relay. The AFC relay supplys power to the EFI ECU, and the injectors. I belive it's a standard Bosch relay, it's located at terminal XVI. The fuel pump relay is a very special unit. It turns the fuel pump on and off, BUT it doesn't do so with the help of the ECU. The fuel pump relay has a bit of electronic wizardy. The first bit is it serves as a rev. limiter for your car. When you get over 6,100 rpm, the fuel pump cuts out. The second is it serves as a fire prevention device. It uses the tach signles to decided if the engine is running our not. It then runs the fuel pump only when the engines running. This away if you get into a car crash it doesn't pump fuel all over averything. The relay is not maped in any way, as far as I know, it's a simple on/off unit. It's located in terminal XVII. If you need more information as to where it's lcoated, go to www.928gt.com The folks at 928 specalists have been kind enough to put fuse and relay charts up on the web.
Extended peroids with the pump jumpered don't seem to hurt it. Before I knew better, the fuel pump on my car had been jumpered to a key controled, fused circurt. The pump ran all the time that the key was on. The same pump is sill running good today, now with the $50 relay.
OK
Because of your tach. and missing issues, I'm willing to bet that it's NOT a EFI issue. That point straight at an ignition issue of some sort. When the car dies, and you try to start it again, do you have spark. If you do not, you have the problem nailed as an ignition issue. From there you can innore the whole EFI system, and deal with the ignition. The fuel pump and the EDU work off the tach signle. This allows the fuel pump relay to decided if it needs to work the rev. limiter, or the engine is running at all. It also tells the ECU how many RPM the engine is running, and thus how long to hold the injectors open. If the ignition system is acting funny, the EFI system will act funny too.
Plug O needs some explaining. I kinda included it in the "wireing" issue. Accorst the bottem of the fuse relay board, there are maybe a dozen and a half multi-colored plugs. Each plug has 8 points that a female connecter will plug into. These plugs run between the wireing in the car, and the wireing behind the fuse relay board. They have letters, A, B, C, D, E, F... from left to right. The werid thing is plug Z is in the middle of everything. I belive O is eighter in the right place, or w/ in one plug of the right place. Plug O is the plug for the ignition system so to speak. If there is too much corrosion there, the whole system will go loopy.
However, here's my distant diagnoises.
You have misses. You have a jumpy tach. You have no spark when it dies. Here's the deal, there are 2 outputs for the inductive box. One for the coil/spark plugs, one for the tach. If you've got an issue with both fo them, they're only connected at one place, the ignition box on the passangers side of the engine bay. This could be a bad box, a bad connecter, a bad grounding, or a bad input to the box.
OK, I've got my paperwork now.
There pretty much isn't a good way to check the box. About the only thing you can do is put a new one in and see if it works. Probably the last coures of action.
The ground is on the metal thing that the hood latchs to, in frount of the car, on the passangers side, underneat the wireing harranss, beside the a/c dryer, assumeing you have a/c.
The connecter for the box is easy to check, pull it off, see if there is any corrosion, or looseness. If so, correct.
Check the green wire. Pull the connecter to the ignition box off. Check the resistance between terminal 7 and 31d. There should be between 485 and 700 ohms. If it's OK, the green wire ohms out OK, as well as the magnetic pick up. Do the same thing, but trying to see if it connects to the ground, if it doesn't your OK. << Eddited in, for additional testing, get a hand powered vacuum pump, and pull a vacuume on both the advance and retard on the distributer, alternatively. The resistance of the whole green wiremagnetic pick up should NOT change. >>
If it's not one of the cheap ones, you need a new box.
It sounds like you need a new box, unfortuntly.
PS, if it turns out you need a new box, your going to want to go through the whole system, and check for a bad peice. A shorted coil, shorted resister, or shorted wireing can cause too much, or too little current through the ignition box, and ruin it. Apperently, an after market coil can do the same thing.
Good luck.
The 82-83 928 has something like 2 relays you need to worry about. There's the AFC relay, and the fuel pump relay. The AFC relay supplys power to the EFI ECU, and the injectors. I belive it's a standard Bosch relay, it's located at terminal XVI. The fuel pump relay is a very special unit. It turns the fuel pump on and off, BUT it doesn't do so with the help of the ECU. The fuel pump relay has a bit of electronic wizardy. The first bit is it serves as a rev. limiter for your car. When you get over 6,100 rpm, the fuel pump cuts out. The second is it serves as a fire prevention device. It uses the tach signles to decided if the engine is running our not. It then runs the fuel pump only when the engines running. This away if you get into a car crash it doesn't pump fuel all over averything. The relay is not maped in any way, as far as I know, it's a simple on/off unit. It's located in terminal XVII. If you need more information as to where it's lcoated, go to www.928gt.com The folks at 928 specalists have been kind enough to put fuse and relay charts up on the web.
Extended peroids with the pump jumpered don't seem to hurt it. Before I knew better, the fuel pump on my car had been jumpered to a key controled, fused circurt. The pump ran all the time that the key was on. The same pump is sill running good today, now with the $50 relay.
OK
Because of your tach. and missing issues, I'm willing to bet that it's NOT a EFI issue. That point straight at an ignition issue of some sort. When the car dies, and you try to start it again, do you have spark. If you do not, you have the problem nailed as an ignition issue. From there you can innore the whole EFI system, and deal with the ignition. The fuel pump and the EDU work off the tach signle. This allows the fuel pump relay to decided if it needs to work the rev. limiter, or the engine is running at all. It also tells the ECU how many RPM the engine is running, and thus how long to hold the injectors open. If the ignition system is acting funny, the EFI system will act funny too.
Plug O needs some explaining. I kinda included it in the "wireing" issue. Accorst the bottem of the fuse relay board, there are maybe a dozen and a half multi-colored plugs. Each plug has 8 points that a female connecter will plug into. These plugs run between the wireing in the car, and the wireing behind the fuse relay board. They have letters, A, B, C, D, E, F... from left to right. The werid thing is plug Z is in the middle of everything. I belive O is eighter in the right place, or w/ in one plug of the right place. Plug O is the plug for the ignition system so to speak. If there is too much corrosion there, the whole system will go loopy.
However, here's my distant diagnoises.
You have misses. You have a jumpy tach. You have no spark when it dies. Here's the deal, there are 2 outputs for the inductive box. One for the coil/spark plugs, one for the tach. If you've got an issue with both fo them, they're only connected at one place, the ignition box on the passangers side of the engine bay. This could be a bad box, a bad connecter, a bad grounding, or a bad input to the box.
OK, I've got my paperwork now.
There pretty much isn't a good way to check the box. About the only thing you can do is put a new one in and see if it works. Probably the last coures of action.
The ground is on the metal thing that the hood latchs to, in frount of the car, on the passangers side, underneat the wireing harranss, beside the a/c dryer, assumeing you have a/c.
The connecter for the box is easy to check, pull it off, see if there is any corrosion, or looseness. If so, correct.
Check the green wire. Pull the connecter to the ignition box off. Check the resistance between terminal 7 and 31d. There should be between 485 and 700 ohms. If it's OK, the green wire ohms out OK, as well as the magnetic pick up. Do the same thing, but trying to see if it connects to the ground, if it doesn't your OK. << Eddited in, for additional testing, get a hand powered vacuum pump, and pull a vacuume on both the advance and retard on the distributer, alternatively. The resistance of the whole green wiremagnetic pick up should NOT change. >>
If it's not one of the cheap ones, you need a new box.
It sounds like you need a new box, unfortuntly.
PS, if it turns out you need a new box, your going to want to go through the whole system, and check for a bad peice. A shorted coil, shorted resister, or shorted wireing can cause too much, or too little current through the ignition box, and ruin it. Apperently, an after market coil can do the same thing.
Good luck.
09-13-2003, 04:56 PM
#15
John,
Think you would have an O plug also. The multi pin plugs under the fuses are labeled from the left starting with A. Think they skip I & L. Mine were labeled with paper tags.
Wouldn't worry about Penn State too much. Think they got caught up in the hoopla of homecoming and didn't prepare for the "weak" competition. Bet it won't happen again.
Bet the same thing happens to OU this year. Probably when they play OSU. Hey, the Saluki's won.
Dennis
Think you would have an O plug also. The multi pin plugs under the fuses are labeled from the left starting with A. Think they skip I & L. Mine were labeled with paper tags.
Wouldn't worry about Penn State too much. Think they got caught up in the hoopla of homecoming and didn't prepare for the "weak" competition. Bet it won't happen again.
Bet the same thing happens to OU this year. Probably when they play OSU. Hey, the Saluki's won.Dennis