Fuel pressure question on my 94

[live2_4x4]

Okay so recently I developed a new symptom. From cold (or more than 20 min sitting) my ex takes two tries to start it on the second try it starts right up no prob, runs great no indication at all that anything is wrong, untill it sits for 20 min or more. Most times it will start 1st try after you prime it with the key 2-3-4 times. I put a fuel pressure tester on and it shows that it does not come up to 35-40 psi when you turn the key the first time or the second sometimes the third usually by the fourth it is up to pressure and will start fine. How do I tell if this is the fault of the pump or the regulator bleeding off the pressure too soon. I also know that it won't hold pressure after it is shut off I assume that this is the check valve in the pump but would this cause my first problem? sorry to be so long winded but I wanted all of the info out front. Thanks for any help!
Glen

 

[CDW6212R]

I have been priming my 93 Explorer twice, for over two years. It starts on the third, ignition on, every time, after being cold. If not primed that way, it often would cough backwards through the intake. That would often blow a vacuum line off. Eventually the fuel vapor being pushed backwords like that, caused the fuel pressure regulator vacuum connector to expand, losing its seal. Check your vacuum connectors.

The system is bleeding pressure down too fast. I don't know if it is the fuel injectors, or something else. I have lived with it, because I knew that I would scrap the whole drivetrain eventually. I'm within a week or two of that change, so hopefully someone else will help you figure it out. Good luck,
Don

 

[vstoval]

Sound like a bad pressure regulator, bad vacuum source at regulator or leaking injectors. Put your pressure guage on it and see if it drops over the 20-30 min. period. If it does then its probably injectors. While the engine is running disconnect the vacuum source at the regulator and measure pressure. Should be between 35-45 psi. with vacuum connected and engine running should be 30-35 psi. If vacuum is present and pressure stays consistantly at 35-45 psi. then its probably a bad regulator. Also a clogged fuel filter could cause the same symptoms.

 

[live2_4x4]

O.K. here goes, the fuel filter is new(less than one week), and it will not hold pressure after shutdown BUT does not bleed down over 20-30min, it drops off to 10-12psi in 30-45 seconds. Whats next?

 

[MrShorty]

If it's losing pressure that fast, then the fuel has to be going somewhere. Since you don't list any other symptoms (ie it runs just fine once started), I would first suspect the check valve in the pump. A bad FPR wouldn't hold pressure, or would be leaking through the vacuum line into the intake which would cause other driveability problems. That fast of a leak through the injectors I would expect to show some driveability problems. And you would be able to smell a leak that fast out of the fuel system.

 

[CDW6212R]

As common as this seems, I'll bet it's an internal leak, back into the fuel system. I never had any other symptoms before. Currently, I have gained an errant stumble, usually off idle. I have also an occasional extra strong exhaust(cat) smell. I believe my catalytic convertors are about gone.

Glen, do not think that your cats are bad. Likely my problem is accelerated by so much stop and go driving. This is my mail vehicle, and is driven 28 miles per day, over a three hour period. This is rough on all drivetrain parts, which is why I am scrapping all of it. Good luck,
Don

 

[live2_4x4]

Thanks guys, the fpr does seem to test ok when running (with and without vac line attached) and does not seem to have visible exterior leaks but I cannot tell if it is leaking into the vac line? Is the check valve replaceable by itself or is it replaced with the fuel pump assembly?
Glen

 

[MrShorty]

" but I cannot tell if it is leaking into the vac line?" -- After running the engine, is there gas in the vacuum line? If not, the FPR isn't leaking into the vacuum line. If there is, then the FPR needs to be replaced.

As for the check valve, I always thought it was part of the fuel pump, but I'm not sure.

 

[falls guy]

My truck had the EXACT same syptoms that got worse and worse for about a year until the pump finally went for a sh.t. I changed the pump and it fires up every time instantly, never stumbles or smells any more at idle because it is now getting proper pressure for the injectors to send a proper mix of air/fuel I guess. I learned that the pumps can still work but with inadequit pressure to run properly. Now I can hardly hear the pump come on it's so quit. It was getting pretty loud before it went. It still made noise, but was no good.
Good luck
Peace

 

[vstoval]

There is a check valve in the pump. If the valve fails pressure could bleed back to the tank.