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2g wont stay running - fuel issue?

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TSiturbo001

20+ Year Contributor
135
18
Nov 16, 2002
Sterling_CT
My 95 Tsi awd stalled while driving yesterday and would not start and stay running for more than 10 seconds. It would not build fuel pressure consistently, would come on intermittently but again the car would only run for a few seconds. Couldn't hear anything out of the pump, no click or whine with key on or trying to start. Its a new Walbro 525 with rewire, Aeromotive AFPR, into a FIC rail with both feed and return lines done. Fuses are good and wiring appears ok. Where do I start? Was going to hit the fuel pump test connection in the bay if it's still there. Will look tonight when I get home. Thoughts?
 
Interesting. I’ve had a 255 since I bought the car almost 3 years ago. Did the rewire no issues. Went to a 525 then started having issues where it would randomly stall. Felt the 12v wire to the pump was hot so I bypassed the rewire and did not stall again so I redid the rewire except for the 12v from battery. Blew a hg a few days later and haven’t check since. Something tells me it might be the pump so I’ll be following this thread.

Are you getting 12v out from the relay?
 
Interesting. I’ve had a 255 since I bought the car almost 3 years ago. Did the rewire no issues. Went to a 525 then started having issues where it would randomly stall. Felt the 12v wire to the pump was hot so I bypassed the rewire and did not stall again so I redid the rewire except for the 12v from battery. Blew a hg a few days later and haven’t check since. Something tells me it might be the pump so I’ll be following this thread.

Are you getting 12v out from the relay?

I need to grab a multimeter and check. The rewire is not good on this car, some of the electrical is bad. Im hoping the pump isnt completely fried now from a poor connection or something. Ill try bypassing too. I need to do more research on the rewire and how everything ties together so I understand it. Something telling me you're probably right though.
 
It’s real easy. Can remember the terminal numbers off hand.

There are 4 terminals,
#30 - 12v to battery
#87 - 12v out
#85 - ground
#86 - switch/trigger

I’m using the factory harness 12v to trigger the relay.

Once the relay gets power to the trigger, it complete the circuit to provide 12v from battery, giving it all the juice.

If you have a spare relay, you can pop that in real quick to see if it’s the relay.

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Last edited:
This is super helpful thank you so much. Will report back

It’s real easy. Can remember the terminal numbers off hand.

There are 4 terminals,
#30 - 12v to battery
#87 - 12v out
#85 - ground
#86 - switch/trigger

I’m using the factory harness 12v to trigger the relay.

Once the relay gets power to the trigger, it complete the circuit to provide 12v from battery, giving it all the juice.

If you have a spare relay, you can pop that in real quick to see if it’s the relay.

You must be logged in to view this image or video.
 
Power at the relay and stock connector. Wonder if this is a cheapo imitation walbro you can find on amazon and it died
 
Might also make sure the fuel regulator (on the end of the fuel rail) isn't bad leaking fuel back to the tank. The pressure should stay for hours/days in the rail when the engine is turned off. But if the regulator is leaking it's gone in seconds. You could temporarily pinch off the return line with a clamp/fingers to see if it stays running after starting. Or just buy a new one as they are cheap.
 
Might also make sure the fuel regulator (on the end of the fuel rail) isn't bad leaking fuel back to the tank. The pressure should stay for hours/days in the rail when the engine is turned off. But if the regulator is leaking it's gone in seconds. You could temporarily pinch off the return line with a clamp/fingers to see if it stays running after starting. Or just buy a new one as they are cheap.

It instantly goes to zero when the pump is off. Ill mess with that too.. the pump is def not working properly but you may have just identified something else too. Thank you! Would I pinch the return line off the rail or after the FPR?
 
It instantly goes to zero when the pump is off. Ill mess with that too..

Sounds like you have an aftermarket FPR? If it's got a gauge in it, you should try pinching after the FPR to see if fuel pressure improves. Can you smell fuel anywhere? A leak such as injector seals would cause the immediate drop in pressure and can actually cause driveablility issues, but not so bad that the motor stalls. But a failing FPR would absolutely cause this problem.
 
Could it be the o-ring in the "bell" on the feed tube where the pump slips in, leaking now? I cut that part out to eliminate the chance of it leaking on my cars and go with a hose and clamps on the pump and the outlet tube of the FP hanger.
 
Could it be the o-ring in the "bell" on the feed tube where the pump slips in, leaking now? I cut that part out to eliminate the chance of it leaking on my cars and go with a hose and clamps on the pump and the outlet tube of the FP hanger.

Will check thanks

Sounds like you have an aftermarket FPR? If it's got a gauge in it, you should try pinching after the FPR to see if fuel pressure improves. Can you smell fuel anywhere? A leak such as injector seals would cause the immediate drop in pressure and can actually cause driveablility issues, but not so bad that the motor stalls. But a failing FPR would absolutely cause this problem.

No smell at all. Seen and had injector seals and o rings go before, this is behaving differently. Gonna look closer at the FPR. Its an Aeromotive A1000 with gauge. Thanks man
 
Ok so I clamped the return tonight and no difference. Started up and ran like garbage for like 10-20secs and instantly died
 
One opinion ive gotten is that the injectors could be stuck open and dirty from being older and on e85.

Would explain why fuel pressure doesnt hold after shutdown or while clamped.

Triple checked rewire and just tried a new relay with same result. Will have a new pump and factory injectors to try hopefully on Wednesday.

I did notice on rewire.. the plastic plug around the 87(power into factory pump plug) was warped and slightly melted. Sounds like what was mentioned here couldve been at play!

Went to a 525 then started having issues where it would randomly stall. Felt the 12v wire to the pump was hot so I bypassed the rewire and did not stall again so I redid the rewire except for the 12v from battery.
 
To rule out stuck open injector, pull the plugs and take a look down the cylinders. If you don’t see anything, crank the engine over by hand a full revolution. I had an injector stuck open and intake valves must have been closed so it filled the intake manifold while I was checking for fuel leak. When I cranked it over, there was fuel everywhere.

Yup my hot wire to the pump was hot to the touch.
 
To rule out stuck open injector, pull the plugs and take a look down the cylinders. If you don’t see anything, crank the engine over by hand a full revolution. I had an injector stuck open and intake valves must have been closed so it filled the intake manifold while I was checking for fuel leak. When I cranked it over, there was fuel everywhere.

Yup my hot wire to the pump was hot to the touch.
Appreciate the explanation. That sounds like a bad time haha.. Im just gonna throw a set of stockers in it and start her up.

You said you re did the rewire and it solved the wiring heating up correct? You didnt change anything else at the same time right?
 
Appreciate the explanation. That sounds like a bad time haha.. Im just gonna throw a set of stockers in it and start her up.

You said you re did the rewire and it solved the wiring heating up correct? You didnt change anything else at the same time right?

Correct. Changed all the wires on the rewire except the 12v to battery. But my hg blew the next day so I haven’t driven it since
 
Update - the pump was bad. It was wired poorly at the battery i think thats what did it in.

New issue that ive just brought on myself now..

I didnt realize there were two versions of the 525. This car had the f90000295 which explains why there was no pressure in the fuel system. That pump doesnt have a check valve. Unfortunately that pump also flows a decent amount more than the 525 f90000285, which is the one I just installed. Its something like 470lph vs 525lph @40psi. My question is do I need to re order a new 295 525? I would have to retune if i keep current pump no? Car is pushing over 500awhp on e85. Its very dialed in. I cant log right now because of an issue with my ecm connection so all I can go off of is afr, which on a 3rd gear pull held around 11.7, but i lifted around 6500 because I got nervous I was gonna run too lean. Thats all i have to go on.
 
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