05 merc mountaineer, fuel pressure issue-updated


#1

An update to my previous post regarding my 05 Merc Mountaineer not starting and the diagnosis that the fuel pump isn’t getting any fuel pressure… Someone on this forum pointed out that the culprit could be the fuel pump control module and I had that replaced, but the car still will sometimes start when turning the key. So far I’ve had the fuel pump replaced, crank shaft sensor replaced, spark plugs, fuel pump relay replaced,new starter, and finally the fuel pump control module. Ford dealership says that I need a new fuel pump to replace the non Ford fuel pump that was installed and fuel rail pressure sensor to the tune of 1400 dollars. At this point, I am at 2000 dollars in repairs, three different repair shops, and Ive learned never to buy American as everyone cautioned me, lol. Any suggestions on what else could be the issue?


#2

Here is your original thread: http://community.cartalk.com/discussion/2295855/merc-mountaineer-no-fuel-pressure#latest

It’s in everyone’s best interest, including yours, to keep the same thread for the same problem. That way everyone can get the full “story” thus far.

If lack of fuel pressure was, in fact, confirmed during no-starts, then I’d be looking for a basic wiring problem. I’d also no be going to a dealer. The quality and trustworthiness does vary, but in general they tend to operate more on margins. It’s easy for them to guess and throw parts because they make money that way. Find a local, owner-operated shop (like the kind where the person’s name on the sign is the same one that works on the car) and have them take a look


#3

I’m going to be zero help here, but I’m having a hard time seeing the pump as being at fault since it was recently replaced and I agree with cigroller this seems more like a wiring or pump control issue.

Has there ever been any codes set related to the fuel pump such as primary circuit failure or whatever?

Keeping in mind that I’m not dead certain on your model, but many Fords use inertia switches and they may be wired in several different ways. One method involves running the fuel pump current directly through the inertia switch and over time this high current draw could cause the switch to become iffy.

The inertia should be easy to check during a no-start, no fuel pressure condition.


#4

ok4450, you are correct that the Merc has an an inertia switch. Its on the passenger side near the door, but under the dash hidden there. The car has no codes when they diagnose it, lol. I had it at Tires Plus one time all day and it started right up each time they cranked it. Sometimes when it starts, it’ll jump up in revs and if I throw it in reverse while it’s still at 2,000 or 3,000 revs it’ll cut right off and go into no start issue for about 7 to 10 minutes. I’ll have the inertia switch checked next, but at this point, the car will probably be traded in for a motorcycle. Not much of a market for a Merc Mountaineer with 135k on it miles and some collision damage on the rear.


#5

“Sometimes when it starts, it’ll jump up in revs and if I throw it in reverse while it’s still at 2,000 or 3,000 revs it’ll cut right off and go into no start issue for about 7 to 10 minutes.”

You have more than just a fuel delivery problem then. Are you quite certain that the lack of fuel pressure was confirmed with a fuel pressure gauge during a no-start situation? Has anyone tested your engine coolant temperature sensor (ECTS)? “Testing,” by the way, doesn’t mean replacing it to see if that makes a difference. It means finding out if the computer is getting an accurate temp reading from the sensor. An ECTS can easily be wrong without throwing a code.

Has anyone checked and cleaned the idle air control valve (IACV)?


#6

I’m going to agree again with cigroller about the IAC valve based on the comment about revving followed by going into a no-start condition.
An IAC problem like that may not set a code or illuminate the CEL either.