[rameam]

Anyone ever have this problem? This is a 91 F150 straight six. Replaced fuel pump, fuel pressure regulator, fuel filter, then plugs, wires, coil, dist cap and rotor. I think that's all.

Only after replacing all this did I come to realize that it wouldn't start until the f.p. turns off. Read about one guy having the same problem, but never read that he solved it. So I'm still looking.

[Jedi_Master]

Howdy rameam...

Hmmm...

Interesting question...

I'm not a Ford man ( Chevy all the way ), does it have Throttle Body Injection (TBI), or just fuel injection per cylinder, and a Throttle Body for air control ?

Reason I ask is if it is TBI, the needle valve could be slightly open causing the fuel to drain back into the tank...

Gotta ask, why did you have to replace all that stuff ?

[rameam]

Because I couldn't figure out what was wrong with it. Only after replacing all the parts did I then discover that the f.p. had to shut off before it would start. It has the manifold f.i..

[Jedi_Master]

Well...like I said I'm not a Ford man, it sounds as if the fuel is draining back into the tank...

From what you say... it sounds as if the fuel lines have no pressure( hence it's why I think the fuel is draining back into the tank somehow ) untill the fuel pump builds it back up...

Might want to look for a inline fuel check valve somewhere ( most are built into the fuel pump, but then again I'm not a ford man and it is an older truck )...


Sorry I couldn't be of anymore help, maybe someone will happen along who knows Fords...

Does the truck have dual tanks, or just a single tank ?

[rameam]

Single tank. The check valve is in the pump. I changed that first (and fuel filter of course). When that didn't solve the problem, I changed the pressure regulator. I figured the electrical parts I replaced probably needed to be replaced anyway. I've been told that I may have a leaky injector, but it seems to me if it was I could smell gas on the dipstick which I cannot. I do hope someone will see this who has had the same problem. I've posted on a couple of automotive forums also. Thanks for your replies.

[Jedi_Master]

One more guess ( and just to give this a bump up )...

I'm going on GM (Ford may be the same), there should be a valve somewhere on the injector rack (the lines that feed the fuel to the injectors). This valve is the one that is used to check the fuel pump pressure, check it and make sure that it isn't leaking...

Also...

Have you checked the fuel lines themselves to make sure that there are no leaks ? Even a small leak can cause the probles you are describing...

Without being there to look at it myself, it does sound like you are loosing pressure somewhere...

[rameam]

I'm sure you're right. It is surely leaking somewhere. I have not checked the pressure because I don't have a gauge. I'll see if I can find something to check it with. I have inserted a drill bit into the shrader valve to see if gas is there. It is present but doesn't squirt out like I think it should.

I will carefully check the lines. It could be leaking where the filter clips in. I don't ever smell any gas however. And I suppose one of the parts I replaced could be bad. Will keep working at it. Thanks for your input.

[Jedi_Master]

Originally Posted by rameam

I have inserted a drill bit into the shrader valve to see if gas is there. It is present but doesn't squirt out like I think it should.

Hmmm...

I think I remember seeing ( when researching your problem ) that the pressure should be around 28~29 psi ( you may want to double check that), so it should have some pretty good pressure behind it when pushing in the valve ( I'm sure you know to always wear safety glasses when doing this, and try and stand away from the valve )...

Originally Posted by rameam

I will carefully check the lines. It could be leaking where the filter clips in. I don't ever smell any gas however. And I suppose one of the parts I replaced could be bad. Will keep working at it. Thanks for your input.

If you know someone who has a gauge ( or sometimes an auto parts place will let you use one they have, may have to call around and see, heck try some of the garages around you and see if they do any free diags, some do some don't, or will let you use their gauge or maybe even rent it to you ), and see if it is holding pressure while running and not running...