Fuel pump issues

[Defend_Dingo]

Okay I got my 86 running with the new transmission temporarily, but only if I pour fuel into the carb directly. I attached a vacuum pump to the inlet side where it should be sucking fuel from the tank and the gauge shows no vacuum when cranking... does the pump need to have fuel in it for it to properly work? This car has been sitting for a while and the fuel system is completely dry

[irowiki]

It is possible the fuel pump just rotted out. You might take it out and run it through the tests in the FSM.

Does not need fuel in it to prime, I've replaced a few fuel pumps and they primed themselves.

Did you replace the fuel filter?

[marlinh]

If it has been sitting for a while the fuel system may need some help. That has happened to me a few times. What has worked for me in the past is to pressurize the fuel tank with compressed air at the filler neck. It helps push the fuel towards the engine. You may still need to start the car with a bit of gas down the carb too.

Where did you have the vacuum gauge hooked up? You can check for pressure on the outlet side of the pump. It is quite low, 4 or 5 psi.

[Petros]

if you are sucking air from the fuel line at the engine bay the solution is simple: find the leak in the fuel line and fix it. Like the pump is okay and the fuel line on the suction side is leaky, so it sucks in air rather than fuel from the tank.

Usually it is one of the rubber flex fuel lines that has degraded and cracked, either right before the fuel pump, or at the fuel filter (either side of it). Also there is a short length of rubber flex fuel line from the tank to the hard line on the underside of the car. That one is hardest to reach.

If the car lived with salty roads, it is also possible one of the hard lines have rusted through, it will only take an inspection to find it.