Strange Shut Down and tears
01-04-2010, 01:13 PM
#31
Chronic Tool Dropper
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Take a look at the electrical diagrams for your car, and see where the fuel pump relay 'trigger' comes from. On all the pre-LH cars, the fuel pump trigger 31b comes from the ignition control unit. It's a pulsed-to-low signal proportional in frequency to engine speed. That same connection is shared by the tachometer. No switch connection from the AFM unit.
Other FPR connections are the 15 bus, on when key is in position 3 or position 4 (engine run or engine start). Connection 30 is from battery through a fuse, and 31 is connected to ground. No connection from 50, which is the 'start' position 4 contact on the ignition switch.
Other FPR connections are the 15 bus, on when key is in position 3 or position 4 (engine run or engine start). Connection 30 is from battery through a fuse, and 31 is connected to ground. No connection from 50, which is the 'start' position 4 contact on the ignition switch.
01-04-2010, 08:05 PM
#32
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Glenn the computer need to sense engine rotation before it energizes the fuel pump, and of course different years may also run the pump when the key is turned
Using the jumper should make the fuel pump run 100% of the time when the jumper is in place.
Very easy to tell if the pump is running at that point, and it removes all the relays etc from the picture.
You should keep one of these in your glove box. it's gotten me home twice now over the years.
Danger is that if the pump is frozen the jumper is carrying a LOT of current. Don't use small gauge wire.
http://members.rennlist.com/v1uhoh/jumping.htm
03-21-2010, 02:02 PM
#34
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I have about 50 in stock and they are $0.20 each.
Roger
Roger
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
03-21-2010, 02:49 PM
#35
Nordschleife Master
An 87+ fuel pump will work on an 86.5 too and iirc they are a little cheaper.
But the first thing I would do is to replace the LH, EZF, and fuel pump relay with NEW 4 or 5 pin Bosch/hella relays.
But the first thing I would do is to replace the LH, EZF, and fuel pump relay with NEW 4 or 5 pin Bosch/hella relays.
03-21-2010, 03:08 PM
#36
Rennlist Member
I replace the fuel pump relay with a jumper when troubleshooting to remove that variable from the equation. My preference is to use a long wired jumper with an on-off switch. I can turn the fuel pump on or off at will from the drivers seat.(that is, if the FP is not the problem) I can leave it in place until I am through troubleshooting or 5000 miles (whichever comes first). Just remember that with the fuel pump jumpered, it will run constantly until you turn it off. 
