Fuel Pressure Again

[Sonny]

Fuel Pressure Goes to 0 whats wrong???

Ok I broke down and bought a Fuel pressure gauge.

The problem ; hard starting and rough idle. Runs fine down hwy, good pickup and 18 mpg.

Here is what I found;

No pressure when gauge hooked up.

Turned key on (not to start) pressure jumped to 40psi then dropped to 2psi in under 10 seconds.

Turned key on again (still not to start) pressure jumped to 65psi then dropped to 2 psi in under 10 seconds again.

Started truck; pressure jumped to 65psi and held steady. Unplugged vacuum from FPR and only got a small deflection in pressure then held steady back at 65psi.

I know by my Chiltons that the pressures are not correct but I still need help in narrowing this down to the correct fault.

I need help. I am not holding pressure. Is there more than one part that could be bad. I have checked for leaks and all is fine.

 

[unclemeat]

Have you replaced the fuel filter?

 

[Sonny]

No I have not replaced the Fuel filter.

Is it possible a filter could cause the drop in pressure. The 65 psi when running I would think would be much lower if it was the filter. It seems to run fine after started. If it was a filter I would expect it to bog down when running down the Hwy.

Thanks for the input, I really want to get this fixed but I do not want to waste money on unneeded parts.

It would be great if it could be the filter, much cheaper than the Fuel pump replacement.

 

[sonik]

Have you ruled out the Fuel Pressure Regulator?

 

[Sonny]

I replaced the Fuel filter today, no change. BTW took me about 5 minutes to change it. Ask me if anyone needs some advice on this.

I believe that on the 1999 it is a returnless system and what would be a FPR is located at the pump. I was thinking the same thing about the FPR. I have searched this board a lot on this problem.

I am just trying to make sure that I have tried all the simple stuff before I change the Fuel pump and find out that was not the problem.

So if anyone has any other thoughts please let me know. I checked with the dealer and the pump is almost$400.00 with tax................

 

[Nate1]

If your pressure drops that quickly after the pump runs for a second, it sounds like something is up. Mabey you have a leak at the tubes near the pump or a leaky injector.
-----Nate

 

[unclemeat]

Fuel pumps usually work or do not work. If it is your fuel pump you should shop around. I don't think motorcraft is acutually making the pump. They just put a sticker on it. You should be able to find a pump for $2 to 300.

Have you dented the gas tank? Fuel pumps use the liquid in the tank for cooling. When you check the fuel pressure is the tank full or empty?

 

[brendan]

Originally posted by nweibley
If your pressure drops that quickly after the pump runs for a second, it sounds like something is up.
-----Nate

You mean that's not normal

 

[Sonny]

Originally posted by nweibley
If your pressure drops that quickly after the pump runs for a second, it sounds like something is up. Mabey you have a leak at the tubes near the pump or a leaky injector.
-----Nate

Is there a sure way to tell if it an injector leaking or if it is the check valve in the pump?

Thanks

 

[Sonny]

Originally posted by unclemeat
Fuel pumps usually work or do not work. If it is your fuel pump you should shop around. I don't think motorcraft is acutually making the pump. They just put a sticker on it. You should be able to find a pump for $2 to 300.

Have you dented the gas tank? Fuel pumps use the liquid in the tank for cooling. When you check the fuel pressure is the tank full or empty?

The tank has no dents and the tank was full when I tested. I am running the tank down now to get ready for the R/R fuel pump.
Thanks

 

[Sonny]

Well I replaced the fuel pump today, not to bad a job except for that fuel fitting and lack of room.

The truck starts like new now, it even seems to have a little more pep.

A little tip on something I did that maybe will help someone else.

If you do this job by yourself take some heavy twine small enough to fit through the front mounting bracket holes, Do both holes and leave enough slack for about 6" of movement. This helps alot when you need to put the tank back up. I just lowered the back enough to get the pump out.

I did use ramps instead of jack stands. It is much safer to me.