There is a fuel pressure switch on the side of my fuel filters ( 87 MCI 6V92 NJT ). Did some searches here and I believe at has something to do with shutdown over ride ??? Regardless, it is leaking fuel. It is a NASON SP-1B-6F. I've tried to get one locally, but no one seems to be able to cross that number over. I've called NASON who referred me to their NYS salesman who is sending me a quote and tells me that any product from them could be 8 to 12 weeks out. Has anyone replaced or eliminated this sender or have an idea where I can get one ?
On a GM that switch is a pressure switch that closes once the engine is running. It is to stop the starter from running if you try to start again so you don't damage the starter.
On an MCI, that switch is normally closed, and provides ground to the starter solenoid. As soon as the fuel pressure is up, it's assumed the engine is running and the switch opens so the solenoid can't operate the starter motor. I personally bypassed it as soon as I installed a priming pump. I connected the ground wire from the solenoid directly to ground. Now I have to make sure I don't try to start the engine when it's running, I lose a failsafe, but I can turn the engine over with my priming pump running.
I changed mine to the oil pressure line as the priming pump would make the starter inoperative.