Fuel pump running problem reoccurring

[ExploreMinnesota]

All right, here's one that has me puzzled. In January of this year, I noticed my fuel pump would sometimes run for a few minutes after shutting my truck off. It would stay on longer each time and eventually it just would not shut off. I figured it was either the fuel pump itself or it was the relay. I have since replaced both of them. The relay appeared to be the culprit. That fix lasted for 3 days and the problem was back. The guy at NAPA agreed to exchange the relay for another new one free of charge. That fixed the problem for several weeks, but then it came back.

What I have discovered is that I can unplug the relay and plug it right back in and the problem goes away for days or weeks. I'm stumped on this one. Is it the relay? Could I have gotten two bad relays from NAPA? I doubt it. Why does unplugging the relay for a brief second or two fix the problem for a while?

Somehow, this has to make sense. Any ideas?

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ExploreMinnesota
91 EB 4x4 Stock

 

[DrewP]

Weird! You may try removing the relay after it sticks and then meter the socket to see if there is some voltage. If there is, then maybe you can trace back the problem to the relay driver. This could be a failure in the computer/electronics. Sorry I can't help more.

Good luck.

Drew

 

[ExploreMinnesota]

Drew,
That's a very logical solution, unfortunately it doesn't work. As soon as I unplug the relay the problem goes away. That tells me there is not a signal coming to the relay. It seems to point to the relay. But how could 3 relays, two of them brand new, exibit the same problem?

I have also disconnected the battery when the problem occurs. When I reconnect the battery, the problem is still there . . . the pump begins running as soon as the battery is reconnected.

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ExploreMinnesota
91 EB 4x4 Stock

 

[Mark R]

I had this same problem on mine...fuel pump stuck on, changed fuel pump relay, 2 weeks later fuel pump sticks on and clicking under hood. This happened right in front of my ford dealer, so while inside I asked why my relays kept going.

The service manager told the parts guy to sell me an EEC (electronic engine control) Relay. Changed it and the problem has not returned.

The fuel pump relay is closest to the firewall, and the EEC relay is the one next to it. The diagram they printed off showed only two relays under the fusebox, but mine had three. On mine it was the middle one, if you have two it is the front one.

Keep the new relay on your fuel pump and buy another relay for your EEC.

Mark

 

[kocke01]

Yes, the ECM relay. I went through the exact same thing. Never understood why, but after putting the new ECM relay in the problem went away and after 2 years hasn't returned. Go figure.

 

[ExploreMinnesota]

Thanks, I'll give that a shot. The problem is back today, so I can't wait to try this.
When I got back to work today after lunch the pump stayed running. I opened the hood and gave the top of the fuse box a good rap with my fist and the relay shut off. That was sure easier than pulling those two boxes out and unplugging the relay.

I have three relays in the bottom box. The fuel pump relay on mine is the middle one . . . at least that's the one they keep giving me.

Thanks for the help!

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ExploreMinnesota
91 EB 4x4 Stock

 

[ExploreMinnesota]

This is an update . . .

The problem appears to be fixed. It's been more than two weeks since I put the new relay in and the problem has not returned.

NAPA told me they only carry the fuel pump relay . . . they don't have the EEC relay. I went to the ford dealer to get it and found out the relay NAPA sold me is the EEC relay, not the fuel pump relay. It will only fits one of the three plugs, so it wasn't that I stuck it in the wrong place. Anyway, I bought the fuel pump relay from Ford and that solved it.

Thanks for all the great help!

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ExploreMinnesota
91 EB 4x4 Stock