Fuel Pump wierdness

[noJeepshere]

So on Saturday I go out to take pics of my electrolysis setup, and when I go to start my Yukon to show the unit working (making bubbles) it won't start! Pull out the multimeter and Chiltons, and start poking around. There is power along the entire circuit for the fuel pump, but it's not buzzing. Hmm... I do a search here, find out that it's about time for them to fail, according to fellow CK5'ers,(10 years or 120,000 miles, both of which it's at) and call the stealership. They want $260 at the student discount for a replacement, and I've got a full tank So today in class, my buddy and I run down to my apartment in his '94 Chevy to tug it up to class. When I turn the key to put it in nuetral, the pump runs! I crank it, and it fires right up!! I'm confused. Now I have a pump for it, but the one in there still works. Do I replace it anyways? I can't afford the pump at the moment, but don't want to get stranded somewhere. I'm doing the filter tomorrow, because it sounds strained, would that cause it to randomly shut off because of too much pressure in the line? School me.

 

[Hogback Fabrication]

I'd go ahead and replace the pump. The electrical/mechanical problem could be in the pump itself and (as you already stated) the pump is due for replacement.

 

[lectric80]

Replace the pump. Whatever caused the initial failure was jarred when you moved it, but it is a temporary fix that will leave you stranded, most likely at the most inopportune time.

 

[noJeepshere]

The thing is is I pounded on the tank with a 2x4 as hard as I dared, and it still didn't work then. Then I go out tonight and voila! it works.

 

[lectric80]

Hitting the tank will have little to no effect on the pump. Most likely the fuel sloshing around brought the pump back to life for a short time, but I wouldn't trust it very far. Even with the cost, it is a small price to pay for the peace of mind of knowing it will start when you turn the key.

 

[Hogback Fabrication]

Hitting the tank will have little to no effect on the pump.

So you're not supposed to fix things by hitting them with 2x4's?

 

[lectric80]

I didn't say that, I just said that hitting the fuel tank with a 2x4 is going to have little effect on the pump. Sometimes hitting things with a BFH or 2x4 is the best medicine. It works well on starters that have a little carbon dust or a dead spot.

 

[Rollcenter]

Replace your pump it is common for them to work intermittently and will leave you stranded at the most in opportune time. Get a Ford F 150 Frame pump and put it outside the tank on the rear frame rail it pumps over 15 psi used this setup on my girlfriends jeep with a 96 chevy v6 in it and I think the junk yards are full of ford f 150s but new its like 45 bucks. the other thing is the filter sock can goop up and when you have a full tank it gets worse then when you let it sit the crap falls away from the sock and runs then it pulls the crap back up and wont pass fuel again. So might be crap in the tank.

 

[dyeager535]

A minor point, but how did it have power all the way to the pump? Without the vehicle running, 12V will only go to the pump to prime the motor, and won't turn back on until you crank the engine.

Only inconsistency I see in your story, it may be nothing, but it's not right unless you left something out, like putting 12V to the fuel pump test lead.