Slow Death
08-05-2003, 12:58 PM
#1
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Slow Death
After recently boasting driving the 80 for the last three years every day, she just went under. I had just finished installing a new speedometer. After the reassembly process I noticed my alternator gauge had stopped working and I still don't have a working odometer. (speedometer works fine) After about 3/4 of a mile the car started loosing the idle like a car running off a generator. I was near a friends house and charged the battery for about 30 minutes, started the car and drove home. When I hit the driveway it did the same thing, just idled down to nothing and died. Almost sounded like the fuel pump was losing it. I am welcome to all suggestions before I start replacing everything that could be a culprit.
08-05-2003, 01:10 PM
#2
Rennlist Member
There is a resistor in the inst. pot that creates the excitation current for the alternator. Several times in the past I have had no charging after working on the pod. The problems you had with the car not runnning sound like the battery voltage dropping. EFI cars will do pretty much exactly this as the voltage drops. On the really old EFI cars (D jet) the mixture gets really rich as the battery depletes, but I am not sure about the Ljets. Your 80 is an L jet, right?
My guess is that the excitation resistor in your pod is somehow not connected resulting in no charging resulting in your EFI crapping out. You may not really have to replace anything so much as fiddle with the connections between the harness and the pod, look carefully at the condition of the flex circuit, and also look at the the connection of the resistor to the flex circuit (it just screws down).
Good Luck
My guess is that the excitation resistor in your pod is somehow not connected resulting in no charging resulting in your EFI crapping out. You may not really have to replace anything so much as fiddle with the connections between the harness and the pod, look carefully at the condition of the flex circuit, and also look at the the connection of the resistor to the flex circuit (it just screws down).
Good Luck
08-05-2003, 01:29 PM
#3
Nordschleife Master
The resistor is in parallel with the warning light on the voltmeter. That's at the low end of the range. If the bulb and resistor are toast, you'll get no charge and no indicator of that.
"Fun" anecdote: I was having some battery draining problems and that light was on constantly. Being new to 928s at the time, I didn't understand how that worked. One day while driving, the resistor gave out along with a bit of smoke. Not nice to see it coming out of the pod. With all of the current now running through the light, it got hot, stank and then melted. Replaced both items, twice, with second install including a rebuilt alternator. No problems since. Except I got the Audi alternator from a local parts shop (on a Sunday) and the vent cowl doesn't fit. When it fries, I'll fix it right.
"Fun" anecdote: I was having some battery draining problems and that light was on constantly. Being new to 928s at the time, I didn't understand how that worked. One day while driving, the resistor gave out along with a bit of smoke. Not nice to see it coming out of the pod. With all of the current now running through the light, it got hot, stank and then melted. Replaced both items, twice, with second install including a rebuilt alternator. No problems since. Except I got the Audi alternator from a local parts shop (on a Sunday) and the vent cowl doesn't fit. When it fries, I'll fix it right.
08-05-2003, 09:45 PM
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Allright, so I charged the battery for a couple of hours, took the bulb assembly from the gas gauge and put it where the one on the alt gauge was bad. Now I get a steady red warning light at the bottom of the gauge and the need isn't doing anything. Am I looking at another voltage regulator, alternator or hopefully something a little cheaper?
08-05-2003, 10:45 PM
#6
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Throwing parts at a 928 problem can get really expensive really quickly.
I would suggest that you go to http://www.nichols.nu/tip692.htm
and learn how to test the alternator and its circuits.
Jim Morehouse has a detailed procedure on the Nichols site. (This is the same Jim Morehouse who has the tech info CDs available - his email is
jim928@ptd.net)
I would suggest that you go to http://www.nichols.nu/tip692.htm
and learn how to test the alternator and its circuits.
Jim Morehouse has a detailed procedure on the Nichols site. (This is the same Jim Morehouse who has the tech info CDs available - his email is
jim928@ptd.net)
08-06-2003, 05:03 AM
#7
FWIW
Similar situation on a rebuilt alt. which worked for a while.
Then while cruising the VM pegged on the low side after the alt light warn and 10ish volt reading for a few minutes.
Got home and shut down in the dark garage noticed alt light was still on even with key on.
This was posted with replies June or July. Only cure was to disconnect battery.
Since the alt. was a lifetime warranted rebuild from O'Rielly's Auto Parts swapped for another- they wouldn't trade out for a chev.- .
Upon installation had MAx charge situation of 16Volts, noticed the Voltage Regulator Pack was the round button type and decided with the advice of Rennlist replys to trot back to the parts store and swap Voltage regulator pack with the Black rectangular one on my old alt.
Problem was cured instantly, but voltage then read on high side of 13 plus volts . I can live with a High 13 plus volts.
Try an alt shop, or, your parts store, o,r Big Three for a VR it is, I believe, the cheapest route.
Similar situation on a rebuilt alt. which worked for a while.
Then while cruising the VM pegged on the low side after the alt light warn and 10ish volt reading for a few minutes.
Got home and shut down in the dark garage noticed alt light was still on even with key on.
This was posted with replies June or July. Only cure was to disconnect battery.
Since the alt. was a lifetime warranted rebuild from O'Rielly's Auto Parts swapped for another- they wouldn't trade out for a chev.- .
Upon installation had MAx charge situation of 16Volts, noticed the Voltage Regulator Pack was the round button type and decided with the advice of Rennlist replys to trot back to the parts store and swap Voltage regulator pack with the Black rectangular one on my old alt.
Problem was cured instantly, but voltage then read on high side of 13 plus volts . I can live with a High 13 plus volts.
Try an alt shop, or, your parts store, o,r Big Three for a VR it is, I believe, the cheapest route.
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08-06-2003, 04:57 PM
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OK, so I take the alternator down to get it checked out, no problem with it. With the engine running the alternator warning light is on and the battery is slowly draining. If I remove the Z! Z2 jumper on the fuse panel the light goes out but the battery still drains. Now I'm thinking it could be a bare wire somewhere. Keep the suggestions coming!
08-07-2003, 05:06 PM
#9
Burning Brakes
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Bare wire suggests to me one more thing that I've heard can do this. A bad ground. I've never had to do it, but there are several (3 I think) ground points under the hood. One on the pass. side where the "jumper " (+) post is and two more on the engine somewhere (if I"m wrong please correct Someone...) Also the connection for ground from the batt. to the body in the back (with the huge wing nut)
If you search the "archives", you'll probably find something on this. - Ruf
If you search the "archives", you'll probably find something on this. - Ruf
08-07-2003, 07:04 PM
#10
Burning Brakes
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Grounds and Electrical Maintenance
I polished up some ground data with some connector maintenance. See link below that probably does not work now:
http://forums.rennlist.com/forums/ul...;f=14;t=007238
See some discussion quotes below about the 7 grounds per the FSM. I’ll add 3 more.
Maintenance:
Coat all electrical connectors with DIELECTRIC GREASE after cleaning/polishing them to enhance conduction and prevent corrosion. Assure that all connections are tight, but not over-torqued.
I would clean every electrical connector I could find. The blade connectors are self cleaning. Cycle them in and out a few times to shine them. You can also use scotchbrite, sandpaper, point files, tiny round files, etc. to polish connectors. For the plugs with 8 or 10 round pins, I use scotchbrite on the male side, and a small round file on the female side.
Replace all old fuses with new ones even if they work perfectly. Be sure to use the right ones. Cycle fuses and relays in and out to polish connectors. See this link, courtesy of 928 Specialists, for fuse and relay charts: http://www.928gt.com/928specs/85-86relay.htm
Ground Points:
Note: Brown wires are solid grounds.
Brown/white wires are switched grounds.
There is a ground, and various connectors beneath the plastic cover, in the spare wheel compartment, above and forward of the battery. Thoroughly clean and coat all of these to help with starting problems. Of course the battery terminals and the bunch of wires attached must be clean, coated, and tight.
2 engine ground cables attached at coil brackets:
- Right side cable goes from coil bracket bolt to topmost front timing belt cover bolt.
- Left side connects at bottom rear of back timing belt cover.
There are a total of 7 ground points. Some easy to get to others you will need to lift the car and climb under. I will try and get you in the right area.
1) Battery negative pole to body in the trunk.
2) Two points separate points above the central electric board.
3) Engine ground to body on right side member. (about a foot forward of firewall, and a foot deep on right hand fender well)
4) Ground point on front left cross member.
5) Ground point on front right cross member.
6) Ground point underneath instrument panel next to steering column.
7) Ground point in trunk at rear right underneath trim panel. (you have to remove the trim panel for access)
This was taken from the shop books.
Listed as follows in the manual:
-Battery negative to body
-Above and behind central electrical panel (2 points)
-Engine to body (under passenger's side)
-Left front cross member (to left of headlight motor)
-Right front cross member (passenger's side)
-Under instrument panel by steering column
-Under right rear side trim panel (inside)
Additionally, my fuel injection harness is grounded to bolts on the passenger's side valve cover.
'83 US 928S 5sp
See this discussion for more data and pictures about grounds. http://forums.rennlist.com/cgi-bin/r...14&t=001295&p=
http://forums.rennlist.com/forums/ul...;f=14;t=007238
See some discussion quotes below about the 7 grounds per the FSM. I’ll add 3 more.
Maintenance:
Coat all electrical connectors with DIELECTRIC GREASE after cleaning/polishing them to enhance conduction and prevent corrosion. Assure that all connections are tight, but not over-torqued.
I would clean every electrical connector I could find. The blade connectors are self cleaning. Cycle them in and out a few times to shine them. You can also use scotchbrite, sandpaper, point files, tiny round files, etc. to polish connectors. For the plugs with 8 or 10 round pins, I use scotchbrite on the male side, and a small round file on the female side.
Replace all old fuses with new ones even if they work perfectly. Be sure to use the right ones. Cycle fuses and relays in and out to polish connectors. See this link, courtesy of 928 Specialists, for fuse and relay charts: http://www.928gt.com/928specs/85-86relay.htm
Ground Points:
Note: Brown wires are solid grounds.
Brown/white wires are switched grounds.
There is a ground, and various connectors beneath the plastic cover, in the spare wheel compartment, above and forward of the battery. Thoroughly clean and coat all of these to help with starting problems. Of course the battery terminals and the bunch of wires attached must be clean, coated, and tight.
2 engine ground cables attached at coil brackets:
- Right side cable goes from coil bracket bolt to topmost front timing belt cover bolt.
- Left side connects at bottom rear of back timing belt cover.
There are a total of 7 ground points. Some easy to get to others you will need to lift the car and climb under. I will try and get you in the right area.
1) Battery negative pole to body in the trunk.
2) Two points separate points above the central electric board.
3) Engine ground to body on right side member. (about a foot forward of firewall, and a foot deep on right hand fender well)
4) Ground point on front left cross member.
5) Ground point on front right cross member.
6) Ground point underneath instrument panel next to steering column.
7) Ground point in trunk at rear right underneath trim panel. (you have to remove the trim panel for access)
This was taken from the shop books.
Listed as follows in the manual:
-Battery negative to body
-Above and behind central electrical panel (2 points)
-Engine to body (under passenger's side)
-Left front cross member (to left of headlight motor)
-Right front cross member (passenger's side)
-Under instrument panel by steering column
-Under right rear side trim panel (inside)
Additionally, my fuel injection harness is grounded to bolts on the passenger's side valve cover.
'83 US 928S 5sp
See this discussion for more data and pictures about grounds. http://forums.rennlist.com/cgi-bin/r...14&t=001295&p=
08-07-2003, 08:23 PM
#11
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Ok, now I'm confused. What is the "Z! Z2" jumper? (Is that a Z1 - Z2?). Z2 is a ground point which connects to bus 31. Z1 comes from your alternator, so a jumper takes it straight to ground?
I had a current drain on my 1980. The simple way to find it is to disconnect your ground strap and stick a 10A rated voltmeter between the battery and battery ground strap and the ground point using the DC current setting on the voltmeter. Hint: Open doors draw 2A so disconnect the hatch switch and push the door switch in somehow while you do this. The current drain should be about 30ma.
If you have enough of a short to kill the car, it is pretty substantial. If you don't find it on the fuse panel, then you may want to check the main wires coming brom the battery to the starter, from the starter to the alternator and from the alternator to the panel. I disconnected the battery and used an ohmmeter to check for continuity with ground on these circuits. It turned out I had a short in the rear wiring harness drawing about 2A which I finally found using the fuse method.
Seeing as you were just in the pod messing with things, that is a suspect area. From the diagrams, it looks like you could disconnect H8 to kill the generator light and see if you still have a short. That circuit is unfused and comes right from the generator via Z6 and Z1. A short anywhere on that path would be pretty severe. The voltmeter and the generator light take pretty different paths. The voltmeter grounds to the steering column (#6 in Thom1's post)
Another thing to check is the harness that comes across the front of the engine. I have been told that it tends to wear and can short over time.
I had a current drain on my 1980. The simple way to find it is to disconnect your ground strap and stick a 10A rated voltmeter between the battery and battery ground strap and the ground point using the DC current setting on the voltmeter. Hint: Open doors draw 2A so disconnect the hatch switch and push the door switch in somehow while you do this. The current drain should be about 30ma.
If you have enough of a short to kill the car, it is pretty substantial. If you don't find it on the fuse panel, then you may want to check the main wires coming brom the battery to the starter, from the starter to the alternator and from the alternator to the panel. I disconnected the battery and used an ohmmeter to check for continuity with ground on these circuits. It turned out I had a short in the rear wiring harness drawing about 2A which I finally found using the fuse method.
Seeing as you were just in the pod messing with things, that is a suspect area. From the diagrams, it looks like you could disconnect H8 to kill the generator light and see if you still have a short. That circuit is unfused and comes right from the generator via Z6 and Z1. A short anywhere on that path would be pretty severe. The voltmeter and the generator light take pretty different paths. The voltmeter grounds to the steering column (#6 in Thom1's post)
Another thing to check is the harness that comes across the front of the engine. I have been told that it tends to wear and can short over time.
08-07-2003, 08:51 PM
#12
Three Wheelin'
Thom, those link did'nt work! Are those threads gone?
I'm moving this from a separate thread.
I'm doing a page on the Factory Ground Points for the 1979 -up 928. To help us all identify and maintain these very important and some times neglected service points. I am taking pictures of mine which should be find for post S4 MYs, but I could use some help from Pre S4 owners with Digital Cameras and knowlege.
Tim, I'm really not trying to hi-jack your thread, just tying to come up with a page that others could be pointed to for help.
From 79 they are listed as:
# 0 Battery negetive strap@
# 1 on front lock member, right.
# 2 at rear of wheel arch underneath right rear trim panel.
# 3 on steering console.*
# 4 on front lock member, left.
# 5 on upper mounting for fuse/relay board*
80 - 83, add
# 6 on front wall.
Do any of you guys know where #1, 2, 4 and 6 are? What the heck is a Front lock member?
NOTE * common to all MY 928 cars, @ common to all MY 928 cars
P.S. Pictures would be a nice touch if possible for # 1, 2, 4 and 6.
There are a total of 7 ground points. Some easy to get to others you will need to lift the car and climb under. I will try and get you in the right area.[/
Thom, I'm looking at the diagrams and for 1979, I see the 5 listed above, from 1980-83 there was 1 added making it six; (6) on front wall. Where would I find the 7th in the book? Or was this one slid in on the sly by Porsche Electrical Dept.?
I'm moving this from a separate thread.
I'm doing a page on the Factory Ground Points for the 1979 -up 928. To help us all identify and maintain these very important and some times neglected service points. I am taking pictures of mine which should be find for post S4 MYs, but I could use some help from Pre S4 owners with Digital Cameras and knowlege.
Tim, I'm really not trying to hi-jack your thread, just tying to come up with a page that others could be pointed to for help.
From 79 they are listed as:
# 0 Battery negetive strap@
# 1 on front lock member, right.
# 2 at rear of wheel arch underneath right rear trim panel.
# 3 on steering console.*
# 4 on front lock member, left.
# 5 on upper mounting for fuse/relay board*
80 - 83, add
# 6 on front wall.
Do any of you guys know where #1, 2, 4 and 6 are? What the heck is a Front lock member?
NOTE * common to all MY 928 cars, @ common to all MY 928 cars
P.S. Pictures would be a nice touch if possible for # 1, 2, 4 and 6.
There are a total of 7 ground points. Some easy to get to others you will need to lift the car and climb under. I will try and get you in the right area.[/
Thom, I'm looking at the diagrams and for 1979, I see the 5 listed above, from 1980-83 there was 1 added making it six; (6) on front wall. Where would I find the 7th in the book? Or was this one slid in on the sly by Porsche Electrical Dept.?
Last edited by T_MaX; 08-08-2003 at 04:58 PM.
08-07-2003, 09:06 PM
#13
Burning Brakes
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Hi Max,
All the links to Rennlist posts that I have been saving for years became invalid with the changeover to the new system. You will need to use the text from my posts to find the posts from which I quoted.
All the links to Rennlist posts that I have been saving for years became invalid with the changeover to the new system. You will need to use the text from my posts to find the posts from which I quoted.
08-07-2003, 09:12 PM
#14
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Max,
I think the 7th was the ground strap connection to the battery.
#1 and #4 are right at the front of the car. Open up the hood and there is a cross piece of metal channel with hoses running along it. The drivers side ground point is pretty obvious, you will find a number of wires bolted to the channel. The passengers side is harder to get to and is on the backside of the channel. See 97-01 in the WSM for pictures.
I think the 7th was the ground strap connection to the battery.
#1 and #4 are right at the front of the car. Open up the hood and there is a cross piece of metal channel with hoses running along it. The drivers side ground point is pretty obvious, you will find a number of wires bolted to the channel. The passengers side is harder to get to and is on the backside of the channel. See 97-01 in the WSM for pictures.
08-07-2003, 09:14 PM
#15
Three Wheelin'
Marc that makes sense, I'll buy that! 
I'l call that # 0
Sorry Marc, I still can't imagine where #1 and 4 is?
Open up the hood and there is a cross piece of metal channel with hoses running along it.
This is what I see when I open the hood (minus mechanical items); Core Support, a Upper Sub-Frame brace (aka strut tower brace), a Sub Frame Rails, Shock towers and a Firewall.
Anyone got pic so I can add them to the page? I don't want to use PWM pics due to copyright in-figment.
I'l call that # 0 Sorry Marc, I still can't imagine where #1 and 4 is?
Open up the hood and there is a cross piece of metal channel with hoses running along it.
This is what I see when I open the hood (minus mechanical items); Core Support, a Upper Sub-Frame brace (aka strut tower brace), a Sub Frame Rails, Shock towers and a Firewall.
Anyone got pic so I can add them to the page? I don't want to use PWM pics due to copyright in-figment.
Last edited by T_MaX; 08-07-2003 at 09:32 PM.