fuel pump works only when the key is in start postion i don't now if its the relay. and i don't know where the relays located:angry:

its the only ride i have honda but motor whent out so having to start the datsun and run and unplug starter and drive and hold the key switch on start postion

Edited January 13, 201114 yr by buddyjackson

Every year is a bit different for the fuel pump circuit. In the '78 (my year), the fuel pump runs with the key in the "start" position and then remains running if there's output from the alternator or oil pressure. If both the alternator goes dead and the oil pressure dies, the pump will shut off. This is controlled by a fuel pump control relay (a different relay from the fuel pump relay). Both relays are located inside the black box on the inside of the passenger side fender in the engine compartment. If the '77 is at all similar, your fuel pump control relay might be out.

Earlier models (I don't remember how much earlier) have a fuel pump shutoff switch in the air flow meter that shuts off the pump if airflow drops below a certain rate.

You should download a copy of the '77 factory service manual. You can find it free, but I forget where.

factory service manuals

http://www.xenons30.com/reference.html

I believe the 77 may have the fuel pump shutoff in the AFM module. Not sure. In any case many of us could speculate where the problem might be, but the fastest way to find it is going to be to look at the circuit diagram, get out a multimeter and start tracking it down. Could be anything. My car had a similar issue, previous owner hooked up a relay backwards and melted the ignition power source wire. The ignition power source is different than the "Start" power source.

The '77 280z has the fuel pump shutoff switch in the air flow meter AFM that shuts off the pump if airflow drops below a certain rate.

If you suspect a relay (i do) they are pretty simple to test with 12 volts and a multimeter. Find the relay in question and follow this video:

Put down the shovel guys