Hey everyone i have a carbed 305 motor ive dropped in, i cant get the fuel pump to prime at all. Ive replaced both fuses, the relay, the fuel pump, i changed out the wiring thats in the cabin to the pump. I changed the ground wire thats on the relay. I cant figure this out. Could the oil pressure sensor be shot? Im getting 12v with the key on to the grey and orange wires. I get 12v for 2 seconds checking tge green ecm wire. I changed out the negative (black/white wire) This is stumping me now.

 

It may be helpful to test the voltage at the connector for the top of the tank, including (or, especially) the ground connection.

 

I changed the tank connectors wires. I used the ground prong on the ground wire while checking my green, orange, and gray wires. All of those wires are getting power and properly

 

If you tested the voltage there while the pump is connected and are still measuring battery voltage, that doesn't leave much but the wiring in the tank and the pump itself.

 

Thats what i was thinking. But i replaced tge entire sending unit and pump already. And i ran 12v straight to the pump and it ran.

 

Voltage means nothing. It has to have current. You need to do a voltage drop test. Voltage is like pressure - current (flow) does the work. You can have 35 psi of air pressure in your tire - it's not flowing anywhere so it's not doing any work. Same with voltage - you can have 12v at the pump but if the wiring has no ability to carry the current, when you apply the load the voltage will drop off to nothing and no work will be performed.

GD

 

Thankyou for the help, im gonna runa drop test, juat curious the oil pressure sensore wires are shot going to the connector could this cause the pump to not turn on too? Or no.

 

I'm not that familiar with carb model F bodies so I'll defer to the crowd for that one. But if you can repair it, you should do so. Oil pressure switches are often used for fuel pump power in carb applications. It's there for a reason and if it's obviously broken then fixing it certainly can only help the overall vehicle reliability quotient.

GD

 

Hi, did you get this sorted? Just a random thought but is the fuel pump wired the correct way round? It'll still run the pump but it obviously wont pull fuel up through it.