Truck Repair: 1989 Chevrolet pickup, oil pressure switch, electric fuel pump

Question
I wanted to say thanks for the advice on my last question. And I have just one more. The problem is with the same truck. 1989 Chevy 4.3 V6. The problem is when the engine is cold, it takes about 30 seconds of cranking to start. When it's warmed up, it will just crank until the battery is dead. If you prime the throttle body it will start right up. Or if you get it rolling and pop the clutch, it will start just fine. Any ideas?
          
                                Thanks. Brad

Answer
Hi Brad,
It has an electric fuel pump inside the tank.
Normally, the pump is operated by a fuel pump relay, probably on the firewall in front of the passenger area.
A backup power supply system for the fuel pump is an oil pressure switch, that supplies power to the fuel pump whenever there is oil pressure.
I think your relay is not working, and the long crank is required to build up oil pressure, then run the fuel pump.
The cold oil builds pressure quicker.
I would wish your oil pressure built quicker, or it might be fine, and the switch slow to work. it is right beside the distributor.

The relay depends on a crank signal from the crank sensor to the ecm, which then runs the fuel pump relay.

The reason for the relay or oil pressure switch, rather than just ignition power to the pump, is so the pump won't keep running in case of a wreck, pumping gas on a hot engine, etc.

You might try some heavier oil, or see why the relay isn't working.

The fuse for the fuel pump is also on the firewall, near the relay. It is kinda hidden in a little black holder screwed to the firewall. Pull the fuse, and jump some battery power to the fuse holder. You should hear the pump running. See if it won't start right up when the jumper is in place.
It won't hurt anything for the pump to run...it runs all the time anyway when the truck is running.

Van