Electric Fuel Pump will not run in 'ON' position

[ZCurves]

I have a 1978 280Z that I have been restoring and I have finished with the engine,etc. under the hood. I wanted to get it up and running to begin the task of adjusting, fine tuning and such. When I turn the key to ON - not Start (although the pump should also run in Start) I am not getting ANY fuel pump buzz. I have had a 78 model for around twenty years and I know the fuel pump should be running initially in the 'ON' position. I have installed a new Fuel Pump and Oil Sender. I have also checked all of the relays and fuses. If I unplug the Oil Sender OR the Alternator, then the fuel pump jumps to life and operates as it should. So, what I need to know is what else could be goofed up that would keep the Fuel Pump from running. Any help would be much appreciated.

[sblake01]

It sounds to me like it's working properly. If you look at the fuel pump operation chart in the 78 FSM in the Engine Fuel section, page EF-15, and also read the text (11-1) on that same page, it doesn't say that the fuel pump would be actuated in the on position until after the engine is started.

[Jeff G 78]

Yep, it only runs in the start position in a '78.

[sblake01]

Yep, it only runs in the start position in a '78.

Well, it only runs in the start position and when he engine is runing with a signal from the alternator and oil pressure switch completing the fuel pump circuit. 78's were the first to have an internally regulated alternator (with a connection for the fuel pump circuit) and the first that didn't have the fuel pump contacts in the AFM. They also have the fuel pump relay under the hood rather than under the dash next to the steering column as the 75-77 did. I've known a few people that ran into problems by attempting to use 78 stuff in a 75-77.

[Jeff G 78]

Well, it only runs in the start position and when he engine is runing with a signal from the alternator and oil pressure switch completing the fuel pump circuit.

Hee, hee. Yes, otherwise it would be a short journey.

[ZCurves]

Gentlemen, Thanks A LOT! sblake01, you were dead on. I must have read that paragraph at least a dozen times; I guess that I was too close and needed to stop and step back. I suppose that when I did not hear the pump buzz then I got spooked and started looking everywhere for a problem. I am certain that I will be needing some more input from you guys in the very near future as I wake my buddy back up from his nap. I only hope that I can help you guys out in the future! Thanks again!!:laugh:

[sblake01]

Well, you just have to remember the differences between the different years of Datsuns. There are some, like my 810, where the fuel pump will run in the on position w/o the engine on long enough to prime the system the it will shut off. That comes in handy if you ever run out of gas.