Alternator/starter/DME/fuel pump
03-05-2019, 12:17 PM
#1
Cruisin'
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Alternator/starter/DME/fuel pump
I fully charged the battery. It reads 12.7 car off and 13.4 with car running at idle. Interesting the dash voltage meter is just above 10. I drove the car making 3 stops and starts, about 20 miles. On the way home it felt like the car would hesitate and then jump, like the fuel pump not getting juice. Voltage meter on the dash now under 10. Back at home the battery reads 13.09 at idle and 12.55 with the car off. Any idea which component is bad? Very infrequent the car won't start unless I charge the batter over night.
03-05-2019, 03:16 PM
#4
Nordschleife Master
If your voltmeter reads 10v when the battery reads 12-14v then I’d start with the ground point in the drivers footwell on the left firewall. That’s a ground for the instrument panel including the voltmeter.
03-05-2019, 03:23 PM
#5
Cruisin'
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Thanks. Also can you help me find the DME cable ground? I read that a faulty DME relay sympton is that the car won't start when warm but will start when it is cold. That has happened.
03-05-2019, 04:02 PM
#6
Nordschleife Master
Thats on the clutch bellhousing, MPIX on the diagram I posted. It’s kind of hard to get to as it’s behind and somewhat under the intake by the firewall. If you trace the longer negative wire from the battery it goes to the bellhousing and right next to that terminal are two other brown ground wires, one of those is the DME ground. Worth cleaning all those grounds wyit but I’ll tell you now, they are sob’s to get to on a 951.
03-05-2019, 05:12 PM
#7
Cruisin'
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I traced the shorter ground from the battery and it appeared to terminate at a 19mm bolt. The last 4 inches the sheathing was off and green copper erosion was there. I took the bolt out however it did not terminate there. I could only feel with my fingers but it seem to terminate to a metal connector of some kind that was coming out of a housing. I couldn't get it off. Any idea? Tomorrow I will try to follow the longer one.
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03-08-2019, 08:22 AM
#8
Drifting
MagK is right on. Sounds like your grounds.
When cleaning the ground on the clutch bellhousing (near the speed/reference sensors), be sure to put a rag or paper towel in the flywheel inspection cutout in the bellhousing. You don't want to drop a nut or socket down there. Ask me how I know...
The top of the bellhousing can be difficult to clean so I do it each time I have the intake off (easier access). I've used a flexible extension on my Dremel w/ a small metal brush bit with good success.
To help, I also put a 'jumper' between the lifting bracket at the back of the head to the firewall (I bought a short pre-made piece of ground cable from Walmart).
When cleaning the ground on the clutch bellhousing (near the speed/reference sensors), be sure to put a rag or paper towel in the flywheel inspection cutout in the bellhousing. You don't want to drop a nut or socket down there. Ask me how I know...
The top of the bellhousing can be difficult to clean so I do it each time I have the intake off (easier access). I've used a flexible extension on my Dremel w/ a small metal brush bit with good success.
To help, I also put a 'jumper' between the lifting bracket at the back of the head to the firewall (I bought a short pre-made piece of ground cable from Walmart).
03-08-2019, 10:17 AM
#9
Two grounds cables from the battery negative terminal, one to the chassis next to the battery and one to the engine on the bellhousing. Pay attention to the comment to cover up the inspection port.
What the cable looks like,
https://www.ebay.com/i/382791248873?chn=ps
sounds like you need a replacement.
https://www.ebay.com/itm/Porsche-944...4383.l4275.c10
https://rennlist.com/forums/924-931-...ml#post5234633
http://elfners.com/944/Iceshark%20Ba...rade%20Kit.pdf
Chassis ground
https://cdn4.pelicanparts.com/techar...arge/pic04.jpg
Engine ground
https://rennlist.com/forums/attachme...ne-grounds.jpg
https://rennlist.com/forums/944-turb...ml#post5727875
What the cable looks like,
https://www.ebay.com/i/382791248873?chn=ps
sounds like you need a replacement.
https://www.ebay.com/itm/Porsche-944...4383.l4275.c10
https://rennlist.com/forums/924-931-...ml#post5234633
http://elfners.com/944/Iceshark%20Ba...rade%20Kit.pdf
Chassis ground
https://cdn4.pelicanparts.com/techar...arge/pic04.jpg
Engine ground
https://rennlist.com/forums/attachme...ne-grounds.jpg
https://rennlist.com/forums/944-turb...ml#post5727875
Last edited by Adker; 03-08-2019 at 02:35 PM.