Fuel Starvation Issues + Noisy Fuel Pump

[422flat6]

The PO of my car had the mixture cranked up super rich. The car ran well but got very poor MPG. Plugs 1-5 were covered with dry black carbon and plug 6 was snow white. I knew something wasn't right with the MFI and set about trying to get it "right". I went through check measure adjust and set everything up correctly. The biggest issue was low fuel pressure at 2.5 psi (!) This must have been causing inadequate fuel delivery to the pump, and the overly rich mixture was compensating for this issue. After cleaning the tank strainer and verifying there was no debris in the bottom of the tank, replacing all fuel lines (supply lines were fossilized and kinked), replacing the fuel filter and replacing the overflow valve I got pressure up to 10 psi and the car ran better. I had a shop with an exhaust gas analyzer adjust the pump mixtures and the car runs great now SOMETIMES with the exception of intermittent stumbling and jerking.

There still seems to be a fuel delivery problem. When the engine gets enough gas it runs great, but it doesn't always get enough gas. The shop recommended relocating the pump to the front since mine is still in the stock 1972 location on the left rear of the torsion tube. I've read all about the benefits of relocating the pump here and on old Pelican threads. I also know Fuel Injection Corp rebuilds these pumps and supposedly does a good job.

While it would be nice to have a freshly rebuilt fuel pump, I don't like just throwing money at a problem. Mine doesn't leak and is capable of 40 psi maximum pressure before the internal bypass valve opens. I have already sent it to Fuel Injection Corp, they bench tested it and sent it back to me saying "it's fine, it makes plenty of pressure, no need to rebuild it". Of course we know pressure isn't the only indicator of a properly function fuel pump. It's also got to deliver enough fuel under all operating conditions.

My pump is super loud and inconsistent sounding. Please listen to it in this Youtube video and tell me if this sounds normal or not. Is this the sound of a weak/dying pump or the sound of cavitation due to the rear-location of the pump? The car is cold in this video, so that should rule out vapor lock due to heat.

https://www.youtube.com/watch?v=V8klTu8myAQ

[lopena]

That certainly does not sound normal to me...the pump should hummmmmmmm smoothly and consistently. Something is definitely amiss in my (admittedly amateur) opinion.

[edmayo]

The rear location is not the problem. Too many of those cars work fine that way. Take the suction hose off the pump and run a direct line from a fuel can into the pump. See how the noise is,,,,that eliminates all possible feed problems of the tank and lines.

[422flat6]

Ed, thank you. I just tried that and the pump sounds fine just pumping in and out of a gas can. I guess I need to look at my fuel lines for any possible restrictions.

[422flat6]

Figured it out. There was a major kink in the suction hose up front where it was routed up and over the steering rack. It was at the apex of that bend up above the rack where it was really hard to see. This modern Viton lined hose I'm using isn't as flexible as the old stuff. I pulled it out and ran it straight to the hard line beneath the steering rack and all is well again.