fuel pump stays on

[lurker01]

93 Explorer (only one motor that year). When i turn the key on (not the engine) the fuel pump comes on (as it should), but does not shut off. When I start the car (it does start after a few attempts), the idle is erratic and the car shuts off after a short period of time. When driving, the car stall, bucks, etc. I replaced the fuel pump relay - no go, same issue. I went to the junk yard yesterday and picked up several different parts (Map [or Maf] sensor and fuel pressure regulater, among other parts).

Anyone have any ideas about what is causing this issue?? I would love some help.

"Some days it's just not worth chewing through the restraints.."

[danielsatur]

The fuel pump requlator should turn the fuel pump off after a certain psi.
Focus on the fuel pump regulator.

[lurker01]

that's my thinking, too, after doing some more research.. I hope it is - I picked up 2 of them at the junkyard yesterday!

"Some days it's just not worth chewing through the restraints.."

[danielsatur]

Doe's it work on vaccum, or a electronic switch?

[shorod]

I doubt that the 93 has a fuel pressure sensor and returnless system. I suspect instead that it's a fuel pressure regulator that returns excess fuel to the tank so if the pump doesn't shut off after priming the system, the regulator won't be the cause of that.

-Rod

[danielsatur]

Maybe the fuel pump is running, but isn't pumping fuel!
Check fuel pressure + filter.

[lurker01]

Originally Posted by danielsatur

Maybe the fuel pump is running, but is it pumping fuel!
Check fuel pressure + filter.

Hmmm..... I have a regulator, so I'll try that first. However, I will replace the filter and check the pressure for sure.....


"Some days it's just not worth chewing through the restraints.."

[way2old]

Swap the fuel pump relay with another of the same size. Ford relays are known to fail quite often.

[lurker01]

Well, been working on it after work the past few days.
Changed the fuel pump relay twice.
Checked all vacuum hoses I could find.
Changed the fuel pressure regulator.
Changed the fuel filter.
Working on borrowing a fuel pressure gauge from a friend.
Starting to look like I'm gonna drop the fuel tank.....we'll see.
Any good ideas about how to drain the fuel tank? I don't have a pump..


"Some days it's just not worth chewing through the restraints.."

[lurker01]

All right - long day.
Replaced the fuel pump relay again - no luck.
Pulled all 6 plugs - 5 were covered in black carbon/soot. Only one was light brown - as it should be. None were wet.
Rented a fuel pressure gauge from Auto Zone ($150) - pressure with key on (not the motor) - reached 40 pounds and stayed there. Turned key off - stayed there - no drop in pressure...... Darn - I was actually hoping it would drop. Bled pressure off and did it again 3 or 4 times. Same results..hmmmm..

Took power distribution box loose and checked for any loose/burned wires - looks ok...

Pulled fuel line off of fuel filter (tank side) - turned key on - plenty of gas coming out. So, the fuel pump comes on, stays on, fuel reaches fuel filter (new) at least. OK, now what?

By the way, the car does not start now... for whatever reason....

I'm thinking - I read somewhere - that there is a PCM (this is the vehicle computer, correct?) relay somewhere...Where? Manual does not mention it that I can find....

Then, I'm thinkin', I'll go to the junkyard and get a PCM (there's a care there in good shape that has only been there a couple of days) and swap it out just, well, just to try something else.

Any good ideas out there? By the way, I can take anything apart and put it back together, but I'm a moron when it comes to electrictiy....


"Some days it's just not worth chewing through the restraints.."

[lurker01]

Well, almost there.
Went to the junk yard and found a 1994 Explorer (mine is a '93) - pulled the PCM out ($28), took it home, plugged it in to my car. Turned the key on - fuel pump came on and went off after about 2-3 seconds!!! Perfect! Started it up. Idles a little rough - little bit of black smoke coming out of the tail pipe - guess it's running a little rich. Check Engine light came on after about 4 seconds. Drove around - got it up to about 50 mph - runs fine, but idles a little rough and CEL stays on. When I turn the car off and restart it, CEL comes back on after a few seconds... So, I am going to check all my vacuum hoses tomorrow and the big plastic air intake 'thing.'

"Some days it's just not worth chewing through the restraints.."

[shorod]

Congrats on getting closer! What diagnostic code(s) is the CEL suggesting?

-Rod

[lurker01]

Drove it to work today - drives fine other than the rough idle.
I plan on taking it over to Advance or AutoZone today or tomorrow to see what code(s) it's giving..

"Some days it's just not worth chewing through the restraints.."