fuel pressure problem help
fuel pressure problem help i have a newly rebuit 95 lt1 355 le2 cam and new walbro 255 kit from racetronix when i first fired it up it ran great for a few days now i get an occsonal stumble and recently the car doesnt always want to start up on the first try. hooked a fuel pressure gage up and i have 41-42psi at idle but when you hit the throddle at all the pressure drops to 38-40psi. going to change the fuel filter tomarrow as a startany other sugestions just kind of wierd this came about all of a sudden. any suggestions would help
Remove the vac line from the reg with the car running & post the pressure results.
This will help determine what the regulator is doing. Currently the engine vacuum changes the pressure so anytime you blip the throttle it will change.
You can also plug the vac line to the engine & take the car for a ride with it removed to see how the pressure reacts while driving.
This will help determine what the regulator is doing. Currently the engine vacuum changes the pressure so anytime you blip the throttle it will change.
You can also plug the vac line to the engine & take the car for a ride with it removed to see how the pressure reacts while driving.
ok changed the filter vacaum hooked up
key forward prime 38psi steady for at least 10min no bleed off
idle 42-43psi now a little improvement
under any throddle 40psi steady
now with vacaum unhooked
prime still 38 psi
idle 43-45 psi
under throddle 43psi steady
after car shut off holds 30psi steady no bleed off
does this mean my next step is regulator? or do these psis seem right?
also my gas gage after install is way off like showing at least a 1/4 tank above what it should.
what do i need to check next would like to get this straightened out
key forward prime 38psi steady for at least 10min no bleed off
idle 42-43psi now a little improvement
under any throddle 40psi steady
now with vacaum unhooked
prime still 38 psi
idle 43-45 psi
under throddle 43psi steady
after car shut off holds 30psi steady no bleed off
does this mean my next step is regulator? or do these psis seem right?
also my gas gage after install is way off like showing at least a 1/4 tank above what it should.
what do i need to check next would like to get this straightened out
The fact that the pressure holds steady at 43, means your pump is OK.
The drop you are experiencing while accelerating is due to engine vacuum pulling the pressure down.
Put a vac gauge on the engine & report what it is at full throttle.
A clogged air filter will pull vac at full throttle & therefore reduce your fuel pressure.
Runung with the vac off the reg will not hurt anything, but the car (computer) will have to learn to compensate at part throttle.
The drop you are experiencing while accelerating is due to engine vacuum pulling the pressure down.
Put a vac gauge on the engine & report what it is at full throttle.
A clogged air filter will pull vac at full throttle & therefore reduce your fuel pressure.
Runung with the vac off the reg will not hurt anything, but the car (computer) will have to learn to compensate at part throttle.
ok but why is the pump not priming to 47 psi like it should?
car kind of acting like it is starving for fuel
what is causing the hard starts here and there?
am i wrong to assume i have something leaking down the pressure or pump not keeping up for some reason
id love to go wot but as the motor has 50 miles on it not really comfortable doing so
car kind of acting like it is starving for fuel
what is causing the hard starts here and there?
am i wrong to assume i have something leaking down the pressure or pump not keeping up for some reason
id love to go wot but as the motor has 50 miles on it not really comfortable doing so
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Prime pressure is rarely the operating pressure. The typical Walbro pump takes longer to prime & will generate less pressure. If you want it to start better, you need to increase the prime time in the tune.
Your pressure is steady at 43 which is fine. 47 is an arbitrary number whereas 43-47 is typically OK. If you had an adjustable regulator you could tweak as necessary.
Since you did not have the pressure numbers from a few weeks ago, you cannot prove it is now different.
It the pressure remains stable through the full throttle rpm range, the pump is OK. Then you have a problem somewhere else.
Your pressure is steady at 43 which is fine. 47 is an arbitrary number whereas 43-47 is typically OK. If you had an adjustable regulator you could tweak as necessary.
Since you did not have the pressure numbers from a few weeks ago, you cannot prove it is now different.
It the pressure remains stable through the full throttle rpm range, the pump is OK. Then you have a problem somewhere else.
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Verdad Gallardo yes 41-43 needle jumping with vac unhooked going down the road car now doesnt really want to start or stay going once started noticed tonight while pump is priming its 45 psi after the pump shuts off goes to 38 so i have something leaking down thinking injector even though they are new also pulled injector fuses car fired right up till ran out of gas going to let it set over night and see if any of the cylinders fire if so injectors and yes thanks for your help so far hopefully i can figure this out
ok heres the latest car currently really hard to start needs throddle pushed to get it to even try at prime it goes to 45psi till pump shuts off if i pull the injector fuses motor fires right up till out of gas
leaky injector? any way to test this without pulling fuel rail as i have bosch 3 with those damn clip on thingys at the bottom that like to fall down the intake port if the oring pushs against it to much.
leaky injector? any way to test this without pulling fuel rail as i have bosch 3 with those damn clip on thingys at the bottom that like to fall down the intake port if the oring pushs against it to much.
ok car is leaking down 10-15 psi immediately after pump stops running hard to start doesnt hold right pressure as going down the road vacum unhooked only keeps pressure around 43 steady if i get car started its running rich and choking its self
leaking injectors???????
leaking injectors???????
