928 intermitent no crank
06-14-2022, 03:08 AM
#31
Rennlist Member
The problem as I understand it:
The starter always functions properly when the car is cold.
The starter often fails (no starter action) when the car is hot.
Jump starting at the battery causes the starter to function after hot failure.
When you turn the key to START, the following sequence of events must occur:
- Power must flow from the ignition switch 50 terminal to terminal 86, the operating coil input, on Relay XIV, the Start Relay.
- Terminal 85, the ground for the operating coil, must be grounded thru the Neutral Safety Start Switch on the transmission. If so, the coil is energized, and the relay operates.
- Terminal 30, the input for the relay contacts, must be connected to battery power. If so, battery power is applied to Terminal 87 of the Start Relay.
- From Terminal 30 of the relay, power flows to a yellow wire on Terminal O5.
- Power flows on the yellow wire to Terminal 14 on the corner of the 14-terminal connector near the jump start terminal.
- Power flows from Terminal 14 to Terminal 50 on the Starter Solenoid. This is one side of a heavy-duty solenoid that both slams the Bendix gear on the starter into engagement and operates a heavy-duty switch connecting the starter motor to the battery connection on the starter. For the solenoid and the motor to operate, the other side of the solenoid must be properly grounded to the chassis. This occurs thru the bellhousing, engine block, and the ground strap connecting the engine block to the chassis. When the solenoid operates, there is a noticeable "clack".
From your descriptions, you hear the "click" of the start relay, but you have never mentioned hearing the "clack" of the starter solenoid.
This gives us some possible causes for the problem.
-As James Bailey suggested, it is possible that the starter solenoid (the heavy solenoid on the starter) needs more power to function than it receives when hot.
- The wire between Terminal 14 and the solenoid may be faulty. The wire harness containing this wire is known to suffer from corrosion and heat damage.
- One or more of the connections and wires between the Start Relay and the solenoid may be heat-sensitive and limiting the power flowing to the solenoid.
One of the major irritants with intermittent faults is, "If it ain't broke, you can't fix it." Since it might not be practical to get under the car to check the power at the solenoid when it fails to start, we need a test rig.
One good way to do this is to hook a test light to the 50 terminal. Get 4' of lamp cord - the brown or white two-conductor wire used to hook a table lamp to the wall outlet - and a 12 volt light bulb. Solder the bulb to one end of the wire so that it burns when power and ground are applied to the other end of the wire. Note how brightly the bulb glows when connected directly to the battery. Attach one conductor to the yellow wire on the 50 terminal of the solenoid, and the other conductor to the solenoid, starter or engine as convenient. Run the wire up the side of the engine and out from under the hood. Tape or wire-tie it to the base of the driver's windshield wiper arm so that the bulb is visible from the driver's seat.
Watch the bulb as you start the car. If the starter fails to operate, there are two possible conditions:
- The bulb will not glow at all, or will glow very dimly. This will indicate a probable fault in the wire harness, or somewhere before that. Move the wire to the output side of Terminal 14 in the 14-terminal connector (the yellow wire on one corner) and repeat the test. If the bulb now glows brightly, but the starter does not work, the harness is the most likely cause, but don't forget the possibility that the ground strap under the engine is faulty when hot.
- The bulb may glow, but the starter does not operate. If the bulb glows, but not as brightly as it did when you tested it on the battery, it may be time to install a Ford starter relay. If the bulb glows brightly but the starter does not operate, the starter solenoid may be failing due to heat. This isn't too common, but can happen.
I hope that this helps...
The starter always functions properly when the car is cold.
The starter often fails (no starter action) when the car is hot.
Jump starting at the battery causes the starter to function after hot failure.
When you turn the key to START, the following sequence of events must occur:
- Power must flow from the ignition switch 50 terminal to terminal 86, the operating coil input, on Relay XIV, the Start Relay.
- Terminal 85, the ground for the operating coil, must be grounded thru the Neutral Safety Start Switch on the transmission. If so, the coil is energized, and the relay operates.
- Terminal 30, the input for the relay contacts, must be connected to battery power. If so, battery power is applied to Terminal 87 of the Start Relay.
- From Terminal 30 of the relay, power flows to a yellow wire on Terminal O5.
- Power flows on the yellow wire to Terminal 14 on the corner of the 14-terminal connector near the jump start terminal.
- Power flows from Terminal 14 to Terminal 50 on the Starter Solenoid. This is one side of a heavy-duty solenoid that both slams the Bendix gear on the starter into engagement and operates a heavy-duty switch connecting the starter motor to the battery connection on the starter. For the solenoid and the motor to operate, the other side of the solenoid must be properly grounded to the chassis. This occurs thru the bellhousing, engine block, and the ground strap connecting the engine block to the chassis. When the solenoid operates, there is a noticeable "clack".
From your descriptions, you hear the "click" of the start relay, but you have never mentioned hearing the "clack" of the starter solenoid.
This gives us some possible causes for the problem.
-As James Bailey suggested, it is possible that the starter solenoid (the heavy solenoid on the starter) needs more power to function than it receives when hot.
- The wire between Terminal 14 and the solenoid may be faulty. The wire harness containing this wire is known to suffer from corrosion and heat damage.
- One or more of the connections and wires between the Start Relay and the solenoid may be heat-sensitive and limiting the power flowing to the solenoid.
One of the major irritants with intermittent faults is, "If it ain't broke, you can't fix it." Since it might not be practical to get under the car to check the power at the solenoid when it fails to start, we need a test rig.
One good way to do this is to hook a test light to the 50 terminal. Get 4' of lamp cord - the brown or white two-conductor wire used to hook a table lamp to the wall outlet - and a 12 volt light bulb. Solder the bulb to one end of the wire so that it burns when power and ground are applied to the other end of the wire. Note how brightly the bulb glows when connected directly to the battery. Attach one conductor to the yellow wire on the 50 terminal of the solenoid, and the other conductor to the solenoid, starter or engine as convenient. Run the wire up the side of the engine and out from under the hood. Tape or wire-tie it to the base of the driver's windshield wiper arm so that the bulb is visible from the driver's seat.
Watch the bulb as you start the car. If the starter fails to operate, there are two possible conditions:
- The bulb will not glow at all, or will glow very dimly. This will indicate a probable fault in the wire harness, or somewhere before that. Move the wire to the output side of Terminal 14 in the 14-terminal connector (the yellow wire on one corner) and repeat the test. If the bulb now glows brightly, but the starter does not work, the harness is the most likely cause, but don't forget the possibility that the ground strap under the engine is faulty when hot.
- The bulb may glow, but the starter does not operate. If the bulb glows, but not as brightly as it did when you tested it on the battery, it may be time to install a Ford starter relay. If the bulb glows brightly but the starter does not operate, the starter solenoid may be failing due to heat. This isn't too common, but can happen.
I hope that this helps...
I am reading your thread since I have also an issue where the voltage on the yellow wire , coming from my starter, is only 8 V instead of 11-12V during cranking
Because of this my car often doesn't fire up during a cold start...I say often, because 2 out 10 times it works....
But engine always cranks, so there I do not have issues. And once engine is warm, I never have starting issues.
So when reading the sequence during starting, is it possible there is an error in what you describe ? :
- Power must flow from the ignition switch 50 terminal to terminal 86, the operating coil input, on Relay XIV, the Start Relay. => shouldn't this be ignition switch 15 terminal
- Terminal 85, the ground for the operating coil, must be grounded thru the Neutral Safety Start Switch on the transmission. If so, the coil is energized, and the relay operates.
- Terminal 30, the input for the relay contacts, must be connected to battery power. If so, battery power is applied to Terminal 87 of the Start Relay. shouldn't terminal 30 be connected to starter and thus only if starter is turning it supplies power to the relay ?
- From Terminal 30 of the relay, power flows to a yellow wire on Terminal O5.
- Power flows on the yellow wire to Terminal 14 on the corner of the 14-terminal connector near the jump start terminal.
- Power flows from Terminal 14 to Terminal 50 on the Starter Solenoid.
I am trying to understand why I am only getting max 8 V on the yellow wire, which provides power to my CSV...
I measured all wires (except the yellow wire directly coming from my starter , terminal 50) and all connections were OK , no corrosion whatsoever. I even replaced the starter relay but this did not solve my issue.
CSV was also tested outside the car and it worked...so I suppose the 8V is a bit low to make my CSV function.
Here is the wire diagram :
06-14-2022, 09:01 AM
#32
... I hate when I read one of these troubleshooting threads and the OP never comes back. I get to the end and... what???
Especially one that's 11 years old...
Cheers
Especially one that's 11 years old...
Cheers
06-14-2022, 09:43 AM
#33
Team Owner
I had a similar issue with the 82 5 speed that I recently restored,
it started great when it was cold .
(NOTE originally the starter was locked up when I got it,
so I took it apart and cleaned it up.)
Then drive it for about 20 miles then try a hot restart after getting gas , no crank.
I tried the #14 pin to the hot post trick and no dice the starter just clicked.
I picked up my keyboard and looked around and found a quality Bosch rebuilt starter.
20 mins later with a swapped starter she starts every time hot or cold.
it started great when it was cold .
(NOTE originally the starter was locked up when I got it,
so I took it apart and cleaned it up.)
Then drive it for about 20 miles then try a hot restart after getting gas , no crank.
I tried the #14 pin to the hot post trick and no dice the starter just clicked.
I picked up my keyboard and looked around and found a quality Bosch rebuilt starter.
20 mins later with a swapped starter she starts every time hot or cold.
06-14-2022, 06:18 PM
#34
Rennlist Member
John, if the relay clicks, he should be getting juice at the starter solenoid? If he checks voltage at the 14 pin connector (starter wire pin), he'll know for sure if the problem is upstream or downstream from there??? I think? I'm not making this up....I think i saw a post one time that said "hit your starter with a hammer" as a solution to this problem
06-14-2022, 06:27 PM
#35
Rennlist Member
if the solenoid is sticking, it might be the time to switch to a high torque starter.....i think i paid only about $50 or so more for mine vs the old school type
06-15-2022, 02:12 AM
#36
Rennlist Member
John, if the relay clicks, he should be getting juice at the starter solenoid? If he checks voltage at the 14 pin connector (starter wire pin), he'll know for sure if the problem is upstream or downstream from there??? I think? I'm not making this up....I think i saw a post one time that said "hit your starter with a hammer" as a solution to this problem
So the voltage on line 50 is transmitted to the solenoid via the starter relay. And this voltage is only 8V during cranking.
06-15-2022, 03:41 AM
#37
Rennlist Member
Wallys last post here was in february 2017.
Starter aren´t expensive:
https://kohl24.de/de/search?page=sea...ds=porsche+928
Starter aren´t expensive:
https://kohl24.de/de/search?page=sea...ds=porsche+928
06-15-2022, 07:25 AM
#38
Rennlist Member
The fact that you motor is cranking tells us that the "low voltage" is not impacting the functionality of the starter motor/solenoid. However when starting the engine this puts a considerable drain on the battery [that is rated in terms of CCA- cold cranking amps] and under normal circumstances I understand the voltage can be expected to drop to around 10.5 volts on really cold starts which you should not have at this time of year. On the later models this supports correct functionality of the engine mangement system but drop below that and problems with starting can occur.
Obviously cold starts put more demand on the system and if the voltage is dropping to 8 volts at this time of year this suggests a problem with either your battery or the windings in the starter motor creating too much resistance- when warm there is less resistance to motion so presumably less drain on the battery so the obvious question is when making hot starts do you still see 8 volts or something higher? Indeed where exactly are you taking such measurement from?
Obviously cold starts put more demand on the system and if the voltage is dropping to 8 volts at this time of year this suggests a problem with either your battery or the windings in the starter motor creating too much resistance- when warm there is less resistance to motion so presumably less drain on the battery so the obvious question is when making hot starts do you still see 8 volts or something higher? Indeed where exactly are you taking such measurement from?
The following users liked this post:
mkhargrove (06-15-2022)
06-15-2022, 05:50 PM
#39
Rennlist Member
The fact that you motor is cranking tells us that the "low voltage" is not impacting the functionality of the starter motor/solenoid. However when starting the engine this puts a considerable drain on the battery [that is rated in terms of CCA- cold cranking amps] and under normal circumstances I understand the voltage can be expected to drop to around 10.5 volts on really cold starts which you should not have at this time of year. On the later models this supports correct functionality of the engine mangement system but drop below that and problems with starting can occur.
Obviously cold starts put more demand on the system and if the voltage is dropping to 8 volts at this time of year this suggests a problem with either your battery or the windings in the starter motor creating too much resistance- when warm there is less resistance to motion so presumably less drain on the battery so the obvious question is when making hot starts do you still see 8 volts or something higher? Indeed where exactly are you taking such measurement from?
Obviously cold starts put more demand on the system and if the voltage is dropping to 8 volts at this time of year this suggests a problem with either your battery or the windings in the starter motor creating too much resistance- when warm there is less resistance to motion so presumably less drain on the battery so the obvious question is when making hot starts do you still see 8 volts or something higher? Indeed where exactly are you taking such measurement from?
86 - at primary ( this is ignition voltage) : 10,5 V
30 - at secondary ( this is voltage towards solenoid and csv) : 8 V
So apparently the power supply of my starter relay is also lower than 12V
Battery voltage with ignition on is 12,4 V
Is this a battery issue or how is it possible that the voltage that powers starter relay (XIV) is quite low?
Which wiring can cause this ?
Is it perhaps all related to my ignition switch? Are the lines 15,30,50,31 coming from my ignition switch
Last edited by GerritD; 06-16-2022 at 02:58 AM.
06-16-2022, 07:07 AM
#40
Rennlist Member
Hi Fred, today I did a recheck and I noticed that on the starter relay I can read the following voltages with ignition on :
86 - at primary ( this is ignition voltage) : 10,5 V
30 - at secondary ( this is voltage towards solenoid and csv) : 8 V
So apparently the power supply of my starter relay is also lower than 12V
Battery voltage with ignition on is 12,4 V
Is this a battery issue or how is it possible that the voltage that powers starter relay (XIV) is quite low?
Which wiring can cause this ?
Is it perhaps all related to my ignition switch? Are the lines 15,30,50,31 coming from my ignition switch
86 - at primary ( this is ignition voltage) : 10,5 V
30 - at secondary ( this is voltage towards solenoid and csv) : 8 V
So apparently the power supply of my starter relay is also lower than 12V
Battery voltage with ignition on is 12,4 V
Is this a battery issue or how is it possible that the voltage that powers starter relay (XIV) is quite low?
Which wiring can cause this ?
Is it perhaps all related to my ignition switch? Are the lines 15,30,50,31 coming from my ignition switch
The wiring conventions read as follows:
Bus 30 is basically any wire that is connected directly to the battery and is live at all times.
Bus 15 is switched on via the ignition switch and are the power circuits needed to start and sustain operation of the engine.
Bus X is switched power via the ignition switch but the circuits are cut off during starting to reduce load on the battery- this generally includes things like lighting and HVAC blower etc.
Bus 31 as I understand is basically parking lights that are illuminated during starting for safety reasons.
Bus 50 is the transient power that energises the starter solenoid.
Igniton switch on means the ignition system is energised but the starter motor is not cranking.
On a relay primary circuit [the actuating coil] 86 is the inlet and 85 is the outlet.
On a relay secondary circuit [the actuated circuit] 30 is the power inlet and 87 is the power outlet.
I trust the above is correct an aligns with your thinking.
If you are seeing 8 volts at the starter relay when the ignuition is switched on but not cranking then something would appear to be "dodgy" or so I would think. The likely suspects would be the ignition switch or a relay- both are known potential problems on aged units and especially 40 year old units if they have not been replaced previously. If there is a problem causing high resistance then it is likely that something will be operating at a higher temperature than would normally be expected. Whether this is the case here remains to be seen.
Last edited by FredR; 06-16-2022 at 07:09 AM.
06-16-2022, 12:11 PM
#41
Rennlist Member
Gerrit,
The wiring conventions read as follows:
Bus 30 is basically any wire that is connected directly to the battery and is live at all times.
Bus 15 is switched on via the ignition switch and are the power circuits needed to start and sustain operation of the engine.
Bus X is switched power via the ignition switch but the circuits are cut off during starting to reduce load on the battery- this generally includes things like lighting and HVAC blower etc.
Bus 31 as I understand is basically parking lights that are illuminated during starting for safety reasons.
Bus 50 is the transient power that energises the starter solenoid.
Igniton switch on means the ignition system is energised but the starter motor is not cranking.
On a relay primary circuit [the actuating coil] 86 is the inlet and 85 is the outlet.
On a relay secondary circuit [the actuated circuit] 30 is the power inlet and 87 is the power outlet.
I trust the above is correct an aligns with your thinking.
If you are seeing 8 volts at the starter relay when the ignuition is switched on but not cranking then something would appear to be "dodgy" or so I would think. The likely suspects would be the ignition switch or a relay- both are known potential problems on aged units and especially 40 year old units if they have not been replaced previously. If there is a problem causing high resistance then it is likely that something will be operating at a higher temperature than would normally be expected. Whether this is the case here remains to be seen.
The wiring conventions read as follows:
Bus 30 is basically any wire that is connected directly to the battery and is live at all times.
Bus 15 is switched on via the ignition switch and are the power circuits needed to start and sustain operation of the engine.
Bus X is switched power via the ignition switch but the circuits are cut off during starting to reduce load on the battery- this generally includes things like lighting and HVAC blower etc.
Bus 31 as I understand is basically parking lights that are illuminated during starting for safety reasons.
Bus 50 is the transient power that energises the starter solenoid.
Igniton switch on means the ignition system is energised but the starter motor is not cranking.
On a relay primary circuit [the actuating coil] 86 is the inlet and 85 is the outlet.
On a relay secondary circuit [the actuated circuit] 30 is the power inlet and 87 is the power outlet.
I trust the above is correct an aligns with your thinking.
If you are seeing 8 volts at the starter relay when the ignuition is switched on but not cranking then something would appear to be "dodgy" or so I would think. The likely suspects would be the ignition switch or a relay- both are known potential problems on aged units and especially 40 year old units if they have not been replaced previously. If there is a problem causing high resistance then it is likely that something will be operating at a higher temperature than would normally be expected. Whether this is the case here remains to be seen.
The strange thing about it, is that once engine is started and run for about 60 secs , I can start it without issues after 1h….Engine is still cold and csv should still spray, not ? Why is it different from day after
06-16-2022, 02:20 PM
#42
Rennlist Member
Fred, I replaced the ignition switch by another one. I did a recheck and now I have 11,5 V at the yellow wire (bus 50) while battery is 12,6 V but during cranking the car only fires up after 10 seconds but slowly comes to life
The strange thing about it, is that once engine is started and run for about 60 secs , I can start it without issues after 1h….Engine is still cold and csv should still spray, not ? Why is it different from day after
The strange thing about it, is that once engine is started and run for about 60 secs , I can start it without issues after 1h….Engine is still cold and csv should still spray, not ? Why is it different from day after
The voltage that matters on the yellow wire is where it connects to the starter solenoid. These cables do not fare well and unless and until you have seen what is inside the cable best not to assume anything about the cable condition. Same for the red cables that go to the hot post that are probably brown by now. After changing the front of engine harness my motor span up much faster and generally fires within about 2 seconds. I cannot comment on the cold start valve- i have no experience with such albeit the analogue will be the same or so I would think.
If the battery is at 12.5 volts then it is in fine condition. Starting to sound as though there is one thing holding your system back whatever it may be.
06-16-2022, 04:59 PM
#43
Rennlist Member
One of the problems I faced was reading 12 v throughout the car. But when adding load, like starting, the ground cable would essentially breakdown...unable to pass enough current due to internal corrosion. Consequently voltage would plunge wherever measured.
In fact, could be driving, hit a bump, which changed the orientation of the ground strap slightly and shut car down. A very corroded one. Could wiggle cable while car was running and shut it down. If dead, could rearrange cable and get it to start. Lovely fun.
In fact, could be driving, hit a bump, which changed the orientation of the ground strap slightly and shut car down. A very corroded one. Could wiggle cable while car was running and shut it down. If dead, could rearrange cable and get it to start. Lovely fun.
Last edited by Landseer; 06-16-2022 at 05:02 PM.
06-16-2022, 06:23 PM
#44
Rennlist Member
Gerrit,
The voltage that matters on the yellow wire is where it connects to the starter solenoid. These cables do not fare well and unless and until you have seen what is inside the cable best not to assume anything about the cable condition. Same for the red cables that go to the hot post that are probably brown by now. After changing the front of engine harness my motor span up much faster and generally fires within about 2 seconds. I cannot comment on the cold start valve- i have no experience with such albeit the analogue will be the same or so I would think.
If the battery is at 12.5 volts then it is in fine condition. Starting to sound as though there is one thing holding your system back whatever it may be.
The voltage that matters on the yellow wire is where it connects to the starter solenoid. These cables do not fare well and unless and until you have seen what is inside the cable best not to assume anything about the cable condition. Same for the red cables that go to the hot post that are probably brown by now. After changing the front of engine harness my motor span up much faster and generally fires within about 2 seconds. I cannot comment on the cold start valve- i have no experience with such albeit the analogue will be the same or so I would think.
If the battery is at 12.5 volts then it is in fine condition. Starting to sound as though there is one thing holding your system back whatever it may be.
I did some further testing today and discovered the following :
1. crank the cold engine after engine did not run after a day : KO, it only fires up after about 10 secs of cranking and slowly creep up in the rpm till 1100 rpm
2. crank the cold engine again 1 minute after it has run in 1. for 1 minute : OK, it fires up directly
3. crank the cold engine again 1 hour later than the run in 2. : OK, it fires up directly
4. crank the cold engine again 3 hours later than the run in 2. : KO, it only fires up after about 10 secs of cranking and slowly creep up in the rpm till 1100 rpm
In all 4 cases, the battery voltage was 13 V with trickle charger connected
I decided to manually bridge my fuel pump, to see if it is a fuel supply issue ( I even let the fuel pump run for 10 secs before starting) : no luck, same issue
A. Could it be related to my WUR ? I suspect this because suppose the control fuel pressure is too high, could this lead to a starting issue?
(I still,need to check my fuel pressures again)
B. When car has started cold, the rpms are 1100.’…shouldn’t this be much higher ?
C. I can also try to test my CSV , mounted outside the intake to see if it sprays during cranking to rule out my CSV
I am almost out of ideas
06-17-2022, 05:35 PM
#45
Rennlist Member
I checked and my cold start injector is spraying :
So this rules out my csv.
more and more I suspect my WUR
I have read that possibly one could tap in
the bold on the WUR holding the bimetallic plate with spring to adjust control pressure only for the cold control pressure…is this correct?
So this rules out my csv.
more and more I suspect my WUR
I have read that possibly one could tap in
the bold on the WUR holding the bimetallic plate with spring to adjust control pressure only for the cold control pressure…is this correct?