Car died with 1/2 tank, Replaced fuel pump, still no start. .78 volt reading at pump. Jumped relay at fuse box, same voltage reading, .78. any ideas, PLEASE.

 

https://www.rx8club.com/series-i-maj...-modes-176491/

This thread has a good wiring diagram for the fuel pump. If you only jumped the fuel relay, it won't have power unless the circuit relay is on too.

 

Thx for reply.
Relay circuit is live. I'm assuming the pump resistor located on the air pump bracket may be cause
Does anyone know how this works? Does the ECU control voltage to the pump? Is there anyway to eliminate the pump speed variability? The resistor costs a fortune!

 

It's basically a 2 speed pump, under load the ecu turns on the second relay which lowers resistance to the pump. Before replacing more stuff, I'd recommend checking voltage where you can along the wiring and connections for the pump to find where the voltage goes away. And just to be sure, you have both of these relays jumped?

 

Thanks so much for your replies!
Took some time, but I finally traced the poor voltage to corrosion on the 60 amp fuse located on the battery terminal. Showed very high resistance due to corrosion I suppose came from exposure to battery electrolyte. Cleaned and replaced, circuit now powers the fuel pump perfectly. While testing the high/low resistor, I decided to relocate above the air pump.
The thread you sent me was perfect!
Thanks again!