I have a '96 Bonneville SE 3800 with a challenging electrical problem.
It started when the car died while driving. After some testing we determined that the fuel pump was bad so it was replaced. That didn't fix it. So time to investigate. This is what I found. When I disconnect the SU (sending unit) and measure the voltage back to the e-conn I get battery voltage until the relay takes it to zero after a few seconds. I then operate the pump on a bench power supply and it works good. I put them together and they don't work. I looked at the e-conn'* and they look fine. I measured the resistance of the SU wire harness and this is what I found + 0.6 Ohms/ - 0.7 Ohms. This seems fine but not sure of specification. I also measure the resistance of the negative lead on the e-conn (from the e-conn to the negative battery terminal) and got 24 Ohms.
I am stumped.
Any suggestions would be greatly appreciated.