97 7.4L ate a fuel pump, fuel tank under vacuum. related?

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GM Guy

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Hey all,

I recently picked up a new project, a 97 C3500 factory regular cab dually pickup, 7.4L factory NV4500, 2wd with G80.

Drove home 150 miles in February, would cut out every couple minutes like it has an ignition problem, I believe if put in neutral or foot on clutch one would find the engine off, but id keep it in 5th, playing with the throttle, then it would come back to life with full power within 10 seconds. When I stopped for fuel it had alot of vacuum in the tank.

Got it home, couple days later took it on a 10 mile trip to town. didnt make it. lol

I can no longer hear the fuel pump, and I believe the reason this truck was dumped at the consignment sale it was at was due to fuel pump problems.

Like my late father always told me, be smarter than the piece of equipment your working with/ find out why the old part failed before ruining a new part.

So I ask you guys, what vents the fuel tank on the vortec 454 trucks? If the tank was under vacuum, i assume that could definitely contribute to burning up pumps?

Also, Delphi seems to be the only quality option on Rock auto, is this the best option or is there an aftermarket solution out there?

Any info appreciated,
Thanks!
 

454cid

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The vacuum? Maybe, but the pumps don't last forever any ways. I currently have a Denso pump in mine. My first guess is the vacuum is a bad gas cap.
 

Schurkey

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I'd expect the gas cap to seal to the filler neck, with all "venting" done via longass hoses and the charcoal canister.

It is somewhat common for the valves on or for the charcoal canister to fail; and it's somewhat common for morons to remove the canister and plug the hoses.

Seems to me that there's a solenoid valve for the canister on the intake manifold of the '97 7.4L.
 

GM Guy

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I figured I'd give an update,

Farming is done for the year so I have a little time to mess with stuff.

Pulled the pump, (through the hole cut by previous owner...hack...) and found a mess! lol

The tubes are all bent to crap and the bottom of the tank is sucked in, so apparently a 454 makes enough vacuum that it can suck the tank in if the purge solenoid is stuck open.

The pump itself looks to have been replaced, as there are screw type hose clamps connecting the pump to the pressure feed tube, versus the new delphi pump having crimp type hose clamps.

The bending of the sending unit while the tank imploded popped the hose off the pump which is apparently when I got stranded. So, till I can order a new tank, new pump went back in the box, old pump got reconnected to pressure feed tube, and old girl runs again!
 
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