Fuel Pressure Leak, No Visible Fuel Leak

[kddrosos]

Good evening everybody,
I have a '95 Talon AWD with a Walbro 255, Aero AFPR, stock filter, stock fuel rail, PTE 880 injectors, and pump rewire just done this weekend. I've been having fuel-related troubles for the last 2 years now which are noticeably getting worse. The car starts, runs normal, and maintains target cruise AFR's. Problem is the fuel pressure is not normal. I know Aero FPR's are notorious for hard starts and bleeding pressure fast. I have resorted to forcing fuel priming via DSMlink V2 due to terrible morning starts (30+ sec of cranking). Car starts no problem now after 10+ sec of priming. When shut off, fuel pressure drops to 0 within 20-30 sec. I really didn't care much until it started affecting with my tunes. I tuned my car this time last year with good results, and it hard-started back then. I recently tuned again after car sat for 9 months and my fuel had to be enrichened almost 10% and timing retarded up to 11° in order to achieve target AFR's with less than 1° of knock. No, that's unacceptable, considering I only retarded up to 3° timing before in similar weather. I can't read fuel pressure during tuning but I can imagine this is due to irregular pressure. I replaced all injector seals shortly before the car sat, and the fuel filter is fairly new as well. So I called RRE, who said to check fuel pump assembly and make sure the O-ring on the pump is sealing properly to the housing. I replaced the seal yesterday and blew into the line. No air leaks now, and old seal was a little stretched out. Problem persists with no change. I open the AFPR and visibly inspect. No torn diaphragm, or chips in the metal. Ball seats correctly and I blew into the return outlet. No air leaks, re-install AFPR, and problem persists. I also considered the pressure-relief valve on the pump opening prematurely. Is it safe to bump up the pressure on the AFPR to see if I can even achieve 85 PSI? The only thing I can think of anymore that would leak air but not visible fuel would be the injectors. Would this behavior describe a leaking injector? Will pulling the spark plugs and smelling the cylinder be enough to check? I hope I left nothing out and I'll attach websites I've researched and 2 "tunes" of before and after characteristics. Both tunes are for 21-22 PSI boost, 93 pump, and feel free to judge. I learned how to tune from tuners' forums . Thank you for any and all help. walloftext.jpg

Tried this, good info but mine was OK: FPR Aeromotive pressure fix - Club DSM Canada

 

[Talyn]

Unless you have access to a scan tool you might have to go to the dealership, I would start by doing an injector balance test, where you pulse each injector individually and observe the pressure drops with a gauge. Or if you can figure out a way to bypass the fuel rail and hook a gauge in, you can see if pressure still drops, I could be wrong, but I don't believe fuel pumps in return systems have any kind of valve, there is really no need to since they just run constantly and the pressure regulator controls the pressure, pretty sure only returnless pumps have a valve. Although if you have a loose connection between your fuel pump and the line, that could cause a pressure issue.

 

[kddrosos]

By scanner do you mean like DSMLink? I'm currently running V2 which can monitor several injector values, fuel trims etc. I just don't know exactly what to look for on the data stream to determine anomalies. I don't have special tools for injector balance testing, but would unplugging individual injectors and looking for RPM drops during idle operation be worthwhile, considering I have blocked off the ISC? I have a fuel pressure gauge on my AFPR after the fuel rail. Also, I've been reading in several other forums that people with leaking injectors are having trouble starting WARM engines. My engine fires right up without priming if it's still somewhat warm, but cold-starts are atrocious. That kind of information encourages me doubt if the injectors are even at fault. Thank you for the help!

EDIT: Additionally, I only originally mentioned the relief valve on the pump because several other threads were saying our Walbros come equipped with them. I just forgot to spot it when i had the pump out. It's not supposed to actuate until 85psi, but if it were to open prematurely during WOT, then that could cause a problem. However, if that were the case, why do I lose ALL pressure within seconds of shut-off? Dilemma...

 

[UrN2nd]

Did u ever figure this out