question about walbro 255lph pump again

90turbo1

Registered User
so here is the problem I am having now.

if car sits for longer than 1 hour the car will not start with out first cycling key from off to run two times. (i have verified the problem is that the fuel system bleeds down to zero pressure.)

now the car runs perfectly when it starts. there is no abnormal smoke or fuel in oil so I am suspecting that the check valve in pump is bad.

does the walbro pump not use a check valve to hold fuel in lines.??

thanks
 
Check the fuel pressure regulator for leaks take off the reference line and see if it spits fuel out, before getting to the pump.
Or a stuck fuel injector.
 
My mustang and S10 did pretty much the same thing. The mustang was leakdown from injectors going bad, s10 was a slight leak at the pressure or return fitting at the TBI unit.

check your fuel filter lines, or if none of the above and not a bad pump i bet you cracked one of the soft lines when you did the pump =-/
 
nope used new piece of flexible pipe in tank. ll lines going to engine and back to tank are not leaking.

fuel filter is not leaking.

have not checked regulator yet. but car runs perfect when it is started. no strange smoke so I dont believe the injectors are leaking down but i could be wrong.
 
so I need to check this car out. I am not believing that the fuel injector or injectors are the problem.

i drove car into shop tonite and was working on interior. so car ran for like 5 min tops. then shut off and let sit for 30-45 min. when I went to start it it was acting like it was flooded and cranked hard then spit and sputtered to life. I could smell what I though was fuel out exhaust.

so I need to check the injectors.

i have to step back a few because I work on return less fuel systems all day and those damn 335 cars with there 3000 plus psi fuel systems. so here is my diagnosis

first start car and let idle stabalize. fuel pressure guage is hooked up to fuel rail. pinch off return line and then shut off motor. observe guage if pressure stays and doesnt drop the problem is with return line and regulator.

if pressure drops then procede to step to.

start up vehicle (return is still pinched off) only do this for a second as to not "dead head pump and destroy it" shut car off and pinch off fuel line before filter under car (if possible, if not at rubber line in engine bay) if pressure doesnt drop with this test the problem is with the fuel pump.

if pressure drops then procede to step 3

with fuel pressure isolated to rail only (both return and pressure line pinched off and pressure drops) its a fuel injector problem.
 
so I need to check this car out. I am not believing that the fuel injector or injectors are the problem.

i drove car into shop tonite and was working on interior. so car ran for like 5 min tops. then shut off and let sit for 30-45 min. when I went to start it it was acting like it was flooded and cranked hard then spit and sputtered to life. I could smell what I though was fuel out exhaust.

so I need to check the injectors.

i have to step back a few because I work on return less fuel systems all day and those damn 335 cars with there 3000 plus psi fuel systems. so here is my diagnosis

first start car and let idle stabalize. fuel pressure guage is hooked up to fuel rail. pinch off return line and then shut off motor. observe guage if pressure stays and doesnt drop the problem is with return line and regulator.

if pressure drops then procede to step to.

start up vehicle (return is still pinched off) only do this for a second as to not "dead head pump and destroy it" shut car off and pinch off fuel line before filter under car (if possible, if not at rubber line in engine bay) if pressure doesnt drop with this test the problem is with the fuel pump.

if pressure drops then procede to step 3

with fuel pressure isolated to rail only (both return and pressure line pinched off and pressure drops) its a fuel injector problem.

Leaking diaphram in the fuel pressure regulator will cause the same symptoms you are experincing. If that is the problem the fuel that leaks goes into the vacuum hose that attaches to the regulator and that fuel dumps directly into the return plenum/intake manifold. Had that same problem with my 91 SC back in 2002.

Like Ricardo already mentioned, you just need to pull the vacuum hose off the regulator or where it attaches to the inlet plenum, cycle the ignition on and off and see if it leaking any fuel.

David
 
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ok so I did these tests today and right off the bat found no leak down.

hmm maybee its sporatic and maybee its not.

i have no fuel in vacuum line from regulator.

ran car till fuel pressure stabalized at 37 psi (vacuum line attached to regulator)

and pinched off return line at rail connection. shut off motor. pressure rose a few psi to 39. vehicle held this pressure for well over 1/2 hour. so...

pump, injectors and lines are ok.

i then released the return line and started vehicle (this time it started right up easily, hmmm strange)

i left fuel guage attached and ran till pressure stabalized again and shut off motor this time I did nothing. vehicle held same 37 to 39 psi for about 1/2 hour and only bled down 1 psi in one hour. Well with in spec.

this time I started vehicle and let idle, the fuel pressure was fluctuating from 33-35 very rapidly. I have seen this on cars with weak regulators in the pas but what strange is it wasnt doing this when I did the first two tests only the last time I started it and everytime after that.

any ideas. I know its some sort of fuel related problem because when the car does the strange starting i can verify there is no pressure till i cycle the key a few times.

anyway.. I think I will replace the regulator for piece of mind soon.
 
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