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GMC V6 and V12 Engines Engine repair and rebuilding

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Old January 31st, 2019, 03:53 PM
Clarke Clarke is offline
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Default Re: 1966 And Later Fuel Pumps

Originally Posted by ilvracn View Post
i still had my old pump laying on the bench from this summer when it went bad. i decided to take it apart, and see what went wrong. one of the check valves fell out. i was driving at hiway speed, i think the vibration from 3400 rpm probably vibrated the valve from it's seat in the pump. diaphram looked excellent. looks like manufacturer defect, should have been staked in.
Interesting... Did the engine die on the road or did it still run?

The first several that went bad on me, I took apart and they had a small tear in the rubber diaphragm towards the outer edge just inside the body flange. Iím assuming this due to having a hard point/edge that the diaphragm is repeatally flexing against? The pumps still worked with tear, but leaks oil from weep hole and Iím assuming you risk getting gas in the crankcase if you continue driving. Luckily, none have left me stranded.

Thanks for sharing.
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Old January 31st, 2019, 05:46 PM
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ilvracn ilvracn is offline
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Default Re: 1966 And Later Fuel Pumps

lost power going up a long hill, pulled the hose off of carb, would still squirt a little gas out. i thought gas gauge was wrong and ran out of gas. a farmer stopped to help, and went and got 5 gal gas. put 4.5 gal in tank, same thing. filled holley carb float bowl from vent hole, got truck running i was able to drive it home. started to run out of fuel in carb again on next hill. backed off of throttle, ran about 1/4 to 1/3 throttle up hill, made it over top of hill. was able to nurse it back, just kept rpm's up and throttle light. i was expecting to have crankcase full of gas but it was ok. changed oil just to make sure and replaced fuel pump.
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