Fuel Pump Failure?

[67Mach1]

Question, can a fuel pump fail in a state that it will allow too much fuel to pas through and flood the carb? Or do fuel pumps fail only in that they quit pumping?

Using a new rebuld QuadraJet from Oreileys, she ran fine at first but it was blowing black smoke. Very rich, so rich it is fouling the plugs. So here is the problem, I turned the screws down all the way to close and it still idles fine. In fact a bit high and only chokes down when I cover the butterflys with my hand.

Last night we checked the timing, pulled and cleaned all the spark plugs and then put a good used Edlebrock 600 CFM 1405 carb on it. She ran for all of about 5 min or less and then flooded, Gas was coming out of the carb.

We tried to crank it a few times then hydrolocked the motor with so much gas. After opening all the plugs to let the presure out we disconnected the fuel line and cranked it over more.

Any Ideas?

[Billla]

You don't note what pump it is; if the pressure is < ~7 PSI then a pump can overwhelm the needle. I don't think this is a failure as much as it is a mismatched pump. If it's an electric vs. mechanical pump, then it's a different discussion as the bypass/return could be blocked.

[67Mach1]

Originally Posted by Billla

You don't note what pump it is; if the pressure is < ~7 PSI then a pump can overwhelm the needle. I don't think this is a failure as much as it is a mismatched pump. If it's an electric vs. mechanical pump, then it's a different discussion as the bypass/return could be blocked.

Sorry, good point.

This is a stock 350 with a mechanical pump. The engine sat up for about 5 years before I basicly got it running again about 9 months ago.

I have no idea what the pressure coming out of the pump is? Guess I need to find out.

[Billla]

No worries If it's a mechanical, I can't think of a way it could fail that would produce higher pressure. My guess is that it's a race-type mechanical pump that's made to be used with a regulator. Definitely want to check the pressure before looking any further - anything over 6-7 means a regulator is required or swap to a street-type aftermarket pump.

I see this problem all the time :/

[FLEET72]

Similar problem 2 different carbs....... Do you have an in-line filter between the pump and carb? Sounds like needles sticking open.

[67Mach1]

Originally Posted by FLEET72

Similar problem 2 different carbs....... Do you have an in-line filter between the pump and carb? Sounds like needles sticking open.

Yes, there is an inline filter.

Thinking it is a carb problem myself. Edlebrock sat for a few months and might have a stuck float, will pull it apart this week to check it out.

Q-Jet ? Thinking a bad rebuild. Or from another post here might have a leak dumping extra fuel into the intake.

Will check it out this weeek also.

I agree with other guy that said he never heard of a fuel pump pushing too much fuel unless it is a higher Pressure unit than needed.