Fuel pressure not ?

[Terry Johnson]

I was sitting in my 99 Explorer last night and turned the key on to put down my window. I was on the phone and didn't turn the ignition back off. After a few minutes I realized my fuel pump was starting up about every 5 second and running for about 7 zeconds. I could tell by tbe whine tbat it was building tbe pressure only in the last 3 seconds of its operation. I have a lean trouble code or 2 and check engine is on. I just want to be sure. This is a bad fuel regulator, right? I haven't heard a fuel pump do this in any other vehicle I've ever been in, but I'm still only guessing. I'm not a tech but am mechanically minded. Am I on the right track. Is it a difficult or expensive fix?

 

[MrQ]

The fuel pump shouldn't be running longer than a few seconds while in RUN, but not START. It just primes the system. There is no fuel pressure information sent to the computer; it only controls the pump and runs it based off the TPS, O2 sensors and a myriad of other inputs. If the pressure is poor with the engine running the system will throw lean codes and then the computer will run the fuel pump more frequently.

Poor design in my opinion. Ford should have long ago added a pressure sensor to the fuel system. It is more efficient.

TLDR: You need to check your fuel pressure before you do anything. It should be about 60 psi for a returnless system.

 

[CDW6212R]

The pump shouldn't run intermittently at all ever. If you think that happened, then the key must have been between positions, and that could alter how the pump runs. That would be the key in the wrong position, never leave it part way between positions. That can cause electrical issues. If it wasn't the key partly between, then there's a problem with the ignition switch, to cause that.

So see if you can duplicate that symptom. If you can't with the key in the correct RUN position, then everything's fine with the control of the pump.

Do check the fuel pressure first thing when you see any lean codes. The 99+ Fords run on 62-65psi fuel pressure. Lean codes will start if it drops to the 60-55psi range. Below that there should be noticeable driveability issues.

 

[Turdle]

If there happens to be a poor or intermittent connection to the PCM power, either in the relay socket or loose connection at the PCM harness, which may cause the PCM power to turn on and off, the fuel pump will run every time the pcm power comes back on. However, you should have also noticed the check engine light turning on and off-



with key on, give the PCM relay and the PCM main connector a jiggle test.
Then,

Go here, and try this free fix. It may or may not help

2nd gen issues? Try this first!