Fuel pump staying on...draining battery

[bitsdoo]

Hello folks,

I've come across a new problem. Went to get into the truck (1991 Explorer Eddie Bauer) today and the battery was dead as a doorknob. The battery is less than a year old so I figure I'm drawing power when the truck is off.

Jumped the truck, no problem, and let the battery charge. Turned the truck back off to start and troubleshoot and I heard the fuel pump still running. Went to the power distribution box and pulled the fuel pump fuse and the pump shut off.

From looking at the wiring diagram it could either be the ECC relay or the fuel pump relay (the power circuit on the ECC feeds the coil on the fuel pump relay). I've tested both relays and they are both switching fine. The resistance across the fuel pump relay is about 60 ohms and the resistance across the ECC relay goes to infinite ohms.

I'd guess the coil in the ECC relay is breaking down...yes? What should the resistance across the coils in these relays be?

Before I do anything I though I'd make sure.

Thanks for all your help in advance.

 

[Opera House]

As relays age, their contact resistance increases which makes them prone to welding. Unless the fuel relay clicks on when inserted, the relay is bad and should e replaced. There is a test connector that has a wire when shorted to ground will turn on the relay, but that would require the ECM relay to be on. Don't overthink this, just get two new relays. If one is bad, it is prudent to replace both.

 

[unclemeat]

I had the same problem last month. It ia pretty simple job. Here are a couple of suggestion to help. Use only motorcraft relays (made in the USA). Use a little spray lubricant on the plastic pieces to let them slide out. Use a dielectric grease to seal the relay the connections. There is a lot of info on the site if you do a search on "fuel pump relay".

 

[bitsdoo]

Thanks for all the help folks. I've done a search on the board and there is alot of info on this inherent problem with 1st gen's.

I will replace both relays but I would like to know which one is causing the problem (honing my troubleshooting skills ;0)).

Am I right in saying that the coil on the ECC relay is the bad one as the resitance is infinite?

What I don't understand is that if the coil is not conducting (infinite resistance) how is the relay even staying energized?

 

[JDraper]

Since the relays are mechanical, it can become stuck in the "on" position without power being applied. When the relay contacts start to get corroded, the contact surface gets rough, and they have a tendency to arc more just before they close. This can cause the relay to "weld" itself in the closed position, causing power to constantly flow. The coil won't show bad in this case.

 

[unclemeat]

I only replace the FPR switch on mine and the probem was solved. I intend to replace the ECU relay when I get around to it.

 

[Crankcase]

Really good chance it is the F.P. Relay.