lift pump runs with key off....

[tfitz4]

My 'new to me' 99 truck had dead batteries this AM.

35,000 miles.
No previous running/performance trouble.
Noticed a small humming/rumble when shut down before, thought it was a typical shut-down noise, never investigated further.
Obviously I was wrong. Lift pump was warm and running, all weekend no doubt.
Trying to recall, but I don't think it was present every time I shut it down, but ambient noise could have masked it.

ECM/Bad Relay/bad pump??? I don't have the shop manuals for this one so I don't know where the signal/feed originates......

Thoughts? Theories? Solutions?

Thanks in advance for the help.

Tom

[john8662]

Sounds like a bad relay. There is a fuel pump relay in the electrical fuse panel underneath the hood. It's possible this thing is sticking or improperly installed (previously replaced).

Check for add-in wiring by any previous riggers too.

J

[DennisG01]

Tom, I can't help in the diagnosis, but it is normal for the lift pump to run a few seconds after you turn the key off. Obviously, what you have going on is not normal. Just offering that for clarification.

[tfitz4]

Sounds like a bad relay. There is a fuel pump relay in the electrical fuse panel underneath the hood. It's possible this thing is sticking or improperly installed (previously replaced).

Check for add-in wiring by any previous riggers too.

J

Thanks John. Relay looked to be OEM Omron(sp), I replaced it on principal. I was able to isolate the pump initially by removing the relay, so hoping that is the fix. Was also able to start the truck and then shut off without the pump running on with the original relay this morning so......will take time to verify fix....if...hoping it was just a sticky relay.
You would think that circuit would be more isolated without the key on...ie no POS feed(term 30), much less the trigger circuit......85-86.

Only wiring mods I have located were 2 interior fuse taps on the Aux and Radio circuits. No cutting or scotchloks found throughout the truck. One of the conditions I was most pleased about when I inspected the truck initially.

Dennis, thanks for the tip on the pump behavior. Good to know.

Thanks again. If anything else jumps to mind, love to hear it.

Tom

[JohnC]

...Noticed a small humming/rumble...

Never heard the lift pump described as a "humming/rumble" before...

Click...Click...Click.....

[tfitz4]

Never heard the lift pump described as a "humming/rumble" before...

Click...Click...Click.....

I think of a facet pump with a clicking. That's what I have on the Disco.
This pump sounds more like the blower fan spinning @ 100rpm....maybe it should be sounding like a click?? Perhaps another symptom that needs addressing....

Tom

[DennisG01]

Never heard the lift pump described as a "humming/rumble" before...

Click...Click...Click.....

Does yours make a click-sound, John? I would describe mine as "purring" (which is the closest thing to a cat I'll ever have!), but I thought the humming/rumble was pretty good. I've only ever been around 4, maybe 5, different 6.5's, but the LP's all sounded the same. I dunno. :)

[JohnC]

You say tomato...

There's a plunger in the pump body that's pushed forward by a spring. When it reaches the end of its travel it is pulled back by a magnet similar to a solenoid... Click. Maybe more like a thunk?