Reign

Car misses under aceleration so I checked the fuel pressure. I attached the guage to the fuel rail and turned the key on engine off. No pressure registers. I start the car and preasure is holding 32psi. I press the accelerator and preasure climbs to about 40psi even when the car is missing. Should I have preasure with they key on engine off? Does this sound like a fuelpump problem or and electrical problem? Has anyone experienced this?



95 Mustang. 5.0 bbk x pipe. mac cold air intake.

sup95cobra

It shouldn't drop right away but it will drop to zero after a little bit, but the pressure you have is fine.

grabbem88

yes it will drop..........look up fuel pressure under grabbem,and you'll learn quite a bit.
like i learned from a wiseman here when you turn the key,and you hear the pump kick on,but when the computer
senses that the car isn't started right a way it will shut off.
what you explained so far your fuel pressure sounds fine.
check your plugs,and check your wires,and make sure no plug wire is leaning on anything,like a dip stick
that will throw spark elswhere.

mississippiheat

Hey,
I had a problem near the same. The motor ran fine while idling, but under accelration it had a miss. I found that the plug wires had went bad. I could see them firing through the boots at night. Made for a good light show. Check your wires with a meter.

roundman

you don't need a meter to check the wires, just put your hand on them with the engine running and if their bad and leaking spark, you will know it real quick!!!!!!!!!! LOL

Kev

If it's fuel pressure due to weak or failing pump you will be able to tell by the way it runs. When mine started going out the engine would not rev over 4k to save my life. To my knowlege, low fuel pressure should not cause a miss, if it's low enough the engine will just sputter like it's running out of gas (because it is!). Before I learned about pressure gages, I used the old flow test. I read that if you disconnect the fuel line and do a flow test; If it flows 16 oz in 30 sec.s then the pump is fine, the regulator is questionable. If it flows less than 16 oz in 30 sec.s then the pump is bad. When I first did the test I used a 16 oz honey jar and thought my pump flowed fine ...... till I realized (what a duffus!) that honey is measured by weight and not by volume! When I got an acurate flow I found that my pump was bad. Changed it out and was happily tearing up the streets once again.
Anyway.. sounds like you need to look, as posted above, to your ignition system.

Kev

Reign

I took the car to a mechanic who had it for 5 days and cound not correct the problem. He suggested replacing the fuel pump. I replaced the fuel pump but this did not correct the problem. I finallly fixed the problem. Turns out all my problems were caused by a Mass Air flow sensor. I took a guess and replaced this and it was a night and day difference. Car runs great now.

bobby

i like your sig. how did u do that? sorry to steal ur post. ignore this......