GTS died
01-23-2009, 08:46 PM
#16
Race Director
OK..
Just checked the injectors..they are getting voltage
Swapped relays, no difference, checked relays they all work...did this with a 9v battery and a multi meter.
I also checked the fuel delivery. I opened a fuel line and relieved the pressure. Cranked it several times and then opened the line again...no fuel. Thinkin' its the pump now.
To check voltage at the pump, does the key need to be turned to the #3 position to get voltage? Can I also disconnect the leads and throw 12v's at it to see if it runs?
Funny, you don't fix a problem for a while and the memory of diagnosing things goes right out the door!
Just checked the injectors..they are getting voltage
Swapped relays, no difference, checked relays they all work...did this with a 9v battery and a multi meter.
I also checked the fuel delivery. I opened a fuel line and relieved the pressure. Cranked it several times and then opened the line again...no fuel. Thinkin' its the pump now.
To check voltage at the pump, does the key need to be turned to the #3 position to get voltage? Can I also disconnect the leads and throw 12v's at it to see if it runs?
Funny, you don't fix a problem for a while and the memory of diagnosing things goes right out the door!
try jumpering the fuel pump relay to get constant on for the fuel pump, then check it for sound & voltage.... One thing I found when my fuel pump was slowly dying was it would run briefly...then die....it turns out once the pump got hot the internal resistance would spike to 15 ohms & stop working...when a good pump is around 1.5 ohms constant....then after it cooled off the resistance would drop and it would briefly start again..... might as well check it....
Now assuming the fuel pump checks out okay for voltage and resistance...how old is the fuel filter?? Maybe some junk got in it and causes a clog?
Yes you could use an independent 12V source to run the pump...(went back and read that)...I did
01-23-2009, 09:01 PM
#17
Be sure to change the internal pump if the other one is shot. There's 99% chance it's a goner also.
01-23-2009, 10:27 PM
#19
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If its the fuel pump, +1 on changing out both of them. IIRC, one of mine went out and it led to the other going out. So I had to change out both. I wanna say that it can run with one of them out. That shortly causes the other to fail. But I'm not certain of that. I'm sure others will chime in on it.
01-23-2009, 10:39 PM
#21
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Repeat after me: dear Lord grant me the serenity to accept the things I cannot change, the courage to change the things I can and the wisdom to know the difference..
01-24-2009, 12:41 AM
#23
i'm willing to bet post 8 wins. 
01-24-2009, 01:38 AM
#24
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Keith:
If you jumper the fuel pump relay as suggested this will answer the point brought out in post #8. Otherwise, the pump only runs when the starter is cranking or the car is running.
If the pump doesn't run, then, as Brian notes, you should check for 12V at the pump lead and good ground on the other lead. If that's present, then you have your answer. For fun, you could try the old shadetree fix of reversing the wires to see if you can clear a jammed pump.
Oh, and for future reference, having voltage at the injectors does not assure they will fire as that requires being taken to ground on one side of the lead, which an internal short would prevent.
If you jumper the fuel pump relay as suggested this will answer the point brought out in post #8. Otherwise, the pump only runs when the starter is cranking or the car is running.
If the pump doesn't run, then, as Brian notes, you should check for 12V at the pump lead and good ground on the other lead. If that's present, then you have your answer. For fun, you could try the old shadetree fix of reversing the wires to see if you can clear a jammed pump.
Oh, and for future reference, having voltage at the injectors does not assure they will fire as that requires being taken to ground on one side of the lead, which an internal short would prevent.
01-24-2009, 02:37 AM
#25
Nordschleife Master
Keith,
Your symptoms were the same as mine when my pump died.
The car ran fine, i went to the gym, when i came out 2 hours later it wouldnt start, towed home and posted here on Rennlist.
I replaced both pumps, problem solved.
Your symptoms were the same as mine when my pump died.
The car ran fine, i went to the gym, when i came out 2 hours later it wouldnt start, towed home and posted here on Rennlist.
I replaced both pumps, problem solved.
01-24-2009, 07:26 AM
#26
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Hi Keith,
Our 1989 928S4 stopped during driving and had to be flatbedded home. Just before this happened there was a discussion thread about fuel pump failures in 928s with about 100K miles. Sure enough it turned out to be the fuel pumps.
Quickest check is to turn on the car, walk to the back and listen for the "angry bee buzz" coming from the back of the car. I didn't here anything and knew instantly what I had. Confirmed later in the garage.
HTH,
Constantine
Our 1989 928S4 stopped during driving and had to be flatbedded home. Just before this happened there was a discussion thread about fuel pump failures in 928s with about 100K miles. Sure enough it turned out to be the fuel pumps.
Quickest check is to turn on the car, walk to the back and listen for the "angry bee buzz" coming from the back of the car. I didn't here anything and knew instantly what I had. Confirmed later in the garage.
HTH,
Constantine
01-24-2009, 11:55 AM
#27
Rennlist Member
A buddy of mine had the same problem. It ended up being one of the fuel pumps. When fuel ran low, one pump did not function. Check both fuel pumps out. Unfortunately, you have to pull the one inside the tank out.
01-24-2009, 12:57 PM
#28
Rennlist Member
I've had cars start or at least cough with a bad fuel pump. If it was running okay but wouldn't restart after a short rest, there should be enough fuel and pressure in the rails to at least fire the engine before the supply runs out. You should be checking output at the fuel rail if you haven't already done so.
Might try checking your battery condition (can't hurt). And use a jumper cable to make sure you have an effective ground to the engine - one clamp on the engine itself and the other to the frame somewhere nearby.
Might try checking your battery condition (can't hurt). And use a jumper cable to make sure you have an effective ground to the engine - one clamp on the engine itself and the other to the frame somewhere nearby.
01-24-2009, 02:08 PM
#30
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Jumping the FP relay was one of the first things done, so we can all settle down over that one
To be honest, I didn't know that was the PSD pump running when the key was in #2 position...thought it was the FP.
I will monkey with the FP's today to diagnose.
To be honest, I didn't know that was the PSD pump running when the key was in #2 position...thought it was the FP.
I will monkey with the FP's today to diagnose.