Weak Link In Fuel Delivery???

[tcndeb]

I've been chasing a problem with my 91 X that I THINK is an intermittent problem with the fuel pump shutting off. Any particular weak points in the electrical side of the fuel delivery system on these trucks?

 

[Alec]

fuel pump relay

 

[tcndeb]

OK. Got a new relay, but can't seem to find it on the truck. Where the heck is it????

 

[Gimp]

Originally posted by tcndeb
Where the heck is it????

On a first-gen Exploder, there is a power distribution box beside the air filter housing. This box has a flip-up cover. The relays and several power fuses will be located inside the power distribution box and a legend will be on the inside cover to identify what each relay and fuse is.

Good luck.

 

[Gimp]

P.S.: I agree that the weak link in the fuel pump electrical on our first-gens is usually the fuel pump relay but the fuel pump can act erratically, too, once they start to go. Has your pump started to become annoying loud (like an electric leaf blower) or has fuel pump electrical noise begun to show up in your stereo or CB? If the fuel pump is shutting off intermittently because of pump overheating, you should be able to take apart your old fuel pump relay and look for signs of high current drain or overheating as well as use a clamp-type DC ampmeter around the fuel pump wire to check for a very high current draw when the pump is running.

Again, good luck.

 

[tcndeb]

The relay seems to be underneath the fuse box. I can see it with a mirror, and got the connector unplugged, but I can't get the relay out...........

 

[Gimp]

On both of my first-gen Exploders, it's not difficult to get to and replace. It's not under the dashboard where the turn signal flasher and hazard warning flasher are. It's under the hood (passenger side) inside the power distribution box that's between the air filter housing and the right front fender. Here's a pic of it with the cover closed (sorry for the dirt).

 

[Gimp]

Here's a pic with the cover open. The legend is on the inside of the cover and in this pic, the fuel pump relay is the white one (Advance Auto Replacement).

Just pull the relay out of its socket and plug the new one in.

Hope this helps.

 

[slow-demon]

The pictures that "gimp" has are of '93 and '94 model years. On the '91 and '92 explorers the relays are indeed underneath the power distribution box. To get a them you need to use a screwdriver and push on the metal tabs (i think it has 2) on the plastic distribution box so you can slide the box up exposing the relays.

 

[Crankcase]

Yeah, 93-94 explorers have the relays in ther top box, but 91-92s have the relays in a seperate box underneath the top fuse box.

You might have to take the EEC test connector off the side of the Power distribution box to get the top part to lift up...

 

[410Fortune]

YES the earlier power dist box is a PITA, in fact it is a great upgrade to go to the junk yard and get the later style box and swap them out (takes some wiring work).
This also leaves you with several open fuse spots and 2-3 relay spots, which you can use to add aftermarket accessories............

I have my relay for my ARB locker, my roof lights, my PIAA, and the fuses in my box, looks very trick and really cleans up the rats nest wiring under the hood.......

Also dont rule out the fuel pressure regulator......

instead of throwing $$$ at it, test the feul pressure first, both when cold and hot, at idle and at higher RPM's, then also test the sucker while parked on a steep hill, what you find might surprise you!!

 

[tcndeb]

Got the relay changed, but the problem is still there. The truck will start, idle fine for a minute, then start trying to stall for a minute or two, then idle fine again. It won't run right long enough to go anywhere, and when the idle starts stumbling the CEL comes on. I pulled a few codes that indicate a problem with the fuel pump circuit, the MAF, and power to pin 1 on the PCM??? Maybe losing voltage to the computer? Whadaya think?

 

[Raschied]

Check the Idle air control valve as well. Although my problem (very similar) did turn out to be the fuel pump relay, a lot of people suggested the IAC.

Check here:

http://www.explorerforum.com/forums/showthread.php?threadid=79206&goto=newpost

 

[tcndeb]

In this case I doubt it's the IAC. The problems also comes and goes regardless if it's at idle or not. It's my understanding that once you get above idle the IAC no longer comes into play. Although I could be misinformed. ;-)

 

[tcndeb]

I put a pressure tester on it tonight, and the fuel pressure is fine. It doesn't drop when the engine tries to die out. Any suggestions? It acts like half the cylinders drop out all at once, then come back...........

 

[tcndeb]

Any way to ohm out the MAF and tell if it's good or not?