no fuel pressure diagnosis

[skelly1]

So, the 1990 has been sitting awhile and I did NOT use any fuel preservative, my bad. Finally got around to putting a battery in it and now its cranks but no start. I determined there is no fuel pressure. There is one connector with 2 wires going to the sending unit/pump at the tank. Then there is a ground securely connected to the chassis. I had 8.7VDC on one of the wires in the plug, and 21mV on the other. I believe that the 21mV is for the sending unit and the 8.7V is for the pump and the pump should be running. I hear nothing. Is it time to pull the tank? Are the voltage numbers above correct? The pump is relatively new, I replaced it a couple years ago then it's been parked. Cheers.

 

[dyeager535]

You shouldn't have voltage to the pump unless the engine is running, cranking, or on it's initial engine prime. Odd that you are seeing 8.7V though, it should be battery voltage or nothing.

There isn't anything complex about that circuit, fuel pump gets 12V on one wire, and it runs, that simple.

 

[skelly1]

I tested with key on, not cranking. If there is one, where is the fuel pump relay located?

 

[readymix]

Firewall, pass side, top, near the air cleaner.

 

[Thunder]

There is a red wire hanging out of the relay. Hook 12 V + from the batt up to it. The pump should run. If you hear the pump running normally the relay is prolly bad.

 

[dyeager535]

You've also got an fuel pump oil pressure switch, so even without the relay you'll get 12V to the fuel pump after a few seconds of engine cranking, assuming that switch isn't dead, which seems pretty uncommon. More common for the fuel pump relays to die.