Thread: 3 fuel pumps? somethings wrong!

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alright, my beloved oll truck <80 3/4 ton 4x4 350 q-jet 4-speed> has been through 3 fuel pumps lately the first 2 were thought to be ultra cheap quality but this new one is fine we thought the pump went out again, but we figured out that its not. it will run fine on an empty tank, i filled it up today ran good for about 5 minutes then it started its crap again like the fuel pump dont work. sit there and crank and crank nothing happens wait a few minutes prime the carb crank it and it'll spit just a tiny bit of fuel at a time just enough to keep it idling, and the filter is like empty. waited a few hours primed it cranked it over and the filter is full as it can be and truck runs good. what the hell!?!?!?!?! its making me mad ive been late for work a few times!

If your fuel pump has two rubber hoses going to it try pinching the small
one with a vicegrip. If it runs well then, you have a problem with the return line. Some trucks had a restricter in the return line.

i have 3 lines, denny i went from 2 of the autozone cheapies to a carter from the place i work at. i work at one of the local hot rod parts stores stocking the floors <bi&*h job> but anyways

thing is, is it only does it with a full tank!

might be a dumb thought make shure all lines are clear and then check the tank vent, run the truck without the cap fully closed. if it stil runs out of fuel my thought would be to pull the tank somthing may have happened to the pickup. there is not much else to check

the other week i did a suburban that the tank was 3/4 full of sugar.... man was that a mess

Originally Posted by gassersrule_196

alright, my beloved oll truck <80 3/4 ton 4x4 350 q-jet 4-speed> has been through 3 fuel pumps lately the first 2 were thought to be ultra cheap quality but this new one is fine we thought the pump went out again, but we figured out that its not. it will run fine on an empty tank, i filled it up today ran good for about 5 minutes then it started its crap again like the fuel pump dont work. sit there and crank and crank nothing happens wait a few minutes prime the carb crank it and it'll spit just a tiny bit of fuel at a time just enough to keep it idling, and the filter is like empty. waited a few hours primed it cranked it over and the filter is full as it can be and truck runs good. what the hell!?!?!?!?! its making me mad ive been late for work a few times!

80 1 ton dually had something wrong with fuel pu took out the left tank and the pickup tube it all checked out fine, could not figure it out, my wife suggested blowing the lines out from the fuel pump with air and the problem was resolved I still never new what the problem was. I did have dual tanks and only one was doing this, but it may be worth a simple experiment. Ed

Summer's here...kids are needing money. Just hire one of the neighborhood kids to sit under the hood as you drive it to keep feeding fuel to it. At least you won't be late to work. Do it quick because minimum wage is going up in July. Seriously, have thought about the fuel baffle in the tank? It created havoc on those models. S series were the worst. But a lot of GM's suffered as well and seemed to only do it when fuel levels were up. When it was low, it worked well. Seems backwards, but it happened a lot. I feel better when I have made double sure that the "sock" was not restricting the pick-up because of fuel additives that have been introduced into the tank over the years. You have a strange situation for sure.

Sounded like your fuel pickup line in the tank messed up.

but it only does it when the gas is full i have no idea,

Originally Posted by DennyW

Ok. Have you checked to make sure the tank is venting ok ? On a full tank, you would have less air in the tank, and it wouldn't take long to suck into a vacuum. On an empty tank, you would have much more room for that. Just tossing ideas.

I'm with Denny on this one, I think you have a vent problem when the tank is full.