Fuel pressure loss in fuel rail | Ford Explorer Forums - Serious Explorations

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Fuel pressure loss in fuel rail

crmorrison3

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Joined
January 21, 2009
Messages
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City, State
Reynoldsburg, Ohio
Year, Model & Trim Level
'94 XLT
I am having a problem with fuel pressure loss when the Explorer is turned off. When I turn the vehicle off I lose fuel pressure and the vehicle is very hard to start. 1994 Ford Explorer XLT 4.0L 4wd.

If I turn the key to activate the fuel pump, wait until it finishes charging the line, then repeat, and then wait a little longer, it starts right away. There are no problems when driving (that I notice). When the fuel system is charged it starts like a champ every time. The fuel rail pressure tests in the normal range when the vehicle is running.

I have had the injectors replaced, replaced the fuel sending unit and pump, and replaced the fuel regulator. There are no fuel leaks (to the ground) and the engine does not burn rich, nor is there any indication that the fuel is leaking into the cyllinders as it always starts right away when I charge the system as described above, and does not blow any smoke. The oil looks just fine and there is no indication that it is leaking there. I get 16.5 mpg which is about what I got before this problem started. I don't smell any gas or have any indication that there is a problem except that it loses fuel pressure quickly when not running, and takes more than one turn of the key to charge it back up before trying to start it if it has been off for more than a few minutes.

The fuel regulator only has the one fuel port that bolts into the fuel rail, and a single vacuum port. It does not have a return line attached to it. However, there are three lines coming from the fuel sending unit to the front of the vehicle.

Is there a return line (to the fuel tank) attached to something else on the fuel rail that I can't easily see? Does anybody have any ideas?

Thanks a bunch!
Charlie
 



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What you describe sure sounds like the check valve in the pump isn't holding pressure. Are you certain the check valve ever worked in this new pump?

And, to clarify misunderstandings:
The fuel regulator only has the one fuel port that bolts into the fuel rail, and a single vacuum port. It does not have a return line attached to it. However, there are three lines coming from the fuel sending unit to the front of the vehicle.

Is there a return line (to the fuel tank) attached to something else on the fuel rail that I can't easily see?
The return line is the one attached to the regulator. The supply line attaches to the fuel rail towards the rear of the engine.
 






Thank you very much for clarifying the return line/supply line. That helps me a immeasurably, because I now understand.

I've been resisting the idea that I replaced a bad part with a brand new bad part (new as in Advance Auto). But with the info you filled in for me, I don't see another possibility. Maybe I dropped some dirt in the line or something... Got any ideas on a way to test for a bad check valve before I drop the tank again?

Thanks again!
Charlie

What you describe sure sounds like the check valve in the pump isn't holding pressure. Are you certain the check valve ever worked in this new pump?

And, to clarify misunderstandings:
The return line is the one attached to the regulator. The supply line attaches to the fuel rail towards the rear of the engine.
 






You're certain there's no fuel leak? I ask because I had one for ohhh...about a year or so. It was seeping from one of the rusted up fittings on top of the pump. You could smell it, but the fuel never touched the ground, just sat on top of the tank. I just recently fixed it with a new pump assembly.
 






Yep, when I put in the new sending unit and fuel pump I actually hooked everything back up and made sure it was dry, and got up and around everything (before mounting it all back in place) to make sure it stayed that way. It stayed dry and did not hold pressure. I moved on and replaced the fuel regulator the next week.

We actually park the thing in the attached garage and there is never a hint of a fuel smell so I really don't think there is a leak.

I've been after this problem for over a year now. There was a lot of rust on the old sending unit and locking ring (all now replaced) and after speaking with you, I wonder if I unknowingly let some get in somewhere it shouldn't have been.

I guess it isn't a huge deal to drop the tank again. I already replaced all the rusted bolts last time. If I do find out that it is the fuel sending unit/pump it will be a real life lesson.

Hmmm... You've given me some things to ponder.
Charlie

You're certain there's no fuel leak? I ask because I had one for ohhh...about a year or so. It was seeping from one of the rusted up fittings on top of the pump. You could smell it, but the fuel never touched the ground, just sat on top of the tank. I just recently fixed it with a new pump assembly.
 






could one of you guys point me to where the fule pressure regulator is? as i'd like to check the vacume line on it to see if there was any fuel in the line, i have a real bad smell comeing from the engine and i've read it would be a good idea to check the line and have a look, but i've searched here and i cant find where the stupid thing is, so if someone could point me in the right direction to the right thread or someone has a pic of where it is i would be most very gratefull thanks
 






FPR is attached to the forward end of the fuel rail on the passenger side, near the thermostat housing/upper radiator hose.
 






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