Is there a check valve, or similar flow directional device, between the lift pump and the fuel filter? I am trying to understand what I can about this area of the fuel system, before I remove the lift pump to further investigate the problem. So far, I have been unable to get any flow through the filter housing.I ensured there is fuel to the lift pump, but I do not see any fuel flowing through the filter housing. This was done by pressurizing the fuel tank and witnessing fuel at the pump fitting. And the fuel filter cap was removed to determine if any fuel flow after the lift pump as it was not witnessed at the banjo test port fitting .I have been using the bump procedure to engage the lift pump and I do hear the lift pump working, though I do not believe it is as noticeable as it has been in the past.Thank you,Gary

The only check valve that I am aware of is on the return line, back between the firewall and the head. The output of the fuel pump to fuel filter should just be the eighth inch stock line. I removed all that on mine, change it all to 3/8's for better fuel flow. I never have liked the banjo bolts for fuel flow, just another limitation for fuel. You never want to starve the injection pump. Those lift pumps, a difficult thing to diagnose. You can hear them, but may not be pumping the fuel. I added BD's aux pump to mine, mounted back by the fuel tank. It comes on when engine oil pressure comes up. Stock pump comes on rigth away, up to 12psi, then when engine is running, oil pressure comes up, aux fuel pump comes on and I get 28 to 30psi. Been running this way for almost 3 years now. No problems at all.Good Luck.

Just because the pump is buzzing doesn't mean the pump is good. These carter stock pumps have a plastic hub inside them that will break free and the pump motor will buzz but the pump rotor is just sitting there... If there is no pressure or flow assume the pump is dead. As for check valve... Nope there is no check valve on the pressure side only the return side of the VP44.

I really hate to say this but if the lift pump croaked, the odds are the VP44 injector pump is damaged too. The VP44 is "fuel lubricated"... and is disappointingly fragile. The new UltraLow Sulpher fuel reduces the lubrication even more. Mike poineered running a bit of 2 cycle oil as a fuel additive to improve the lubricosity of the fuel. I'm not sure if it would help the injector pump survive a lift pump failure. Russ

I wouldn't want to personally try that Russ but I beat it would aid for a short time but the lack of extra fuel flow would eventually kill it I'm sure... Like running a engine without a constant oil pressure eventually the bearings will fail...

I know, if the lift pump died, all bets are off!Russ