2005 cavalier electrical issue

[love0126]

Hi everybody. Im writing because I thought I had a bad fuel pump (again). Turns out the fuel pump is good. When cranking, the fuel pump relay shows 12 volts on only one terminal. The upper right. When tracing it back, the block where the harness from the fuel pump plugs in shows twelve volts. However, the fuel pump doesn't run. I disconnected the harness and jumped the fuel pump terminals directly. The car runs great when I do this, except for a check engine light. I am going to pull the codes later today. I wanted to know if anyone has had an issue with the ecm going bad, etc. Any suggestions would be appreciated.

[jeepkiller]

I had a very similar problem on a blazer buy the haynes manual for your Cavalier maybe you could find some place where the wires have short circuited or some type of relay hidden somewhere like in my blazer sorry if I can't help more though

[love0126]

Thankfully I was able to fix the problem. I will now describe that process.

First thing I did was re-check the resistance from terminal #30 from the fuel pump relay under the hood to the fuel pump positive wire just before it enters the fuel tank harness (thanks to a wire I had soldered in just for the emergency occasion if this darn thing decides not to work again. Saved my butt the next day) I just about dropped my jaw when my multimeter read 700 K Ohms. Then I traced the harness back into the firewall. The fuel pump + wire then went into connector 200 (in the driver's kickpanel) at terminal W. I noted excessive melting at terminal W upon closer inspection. I checked resistance from this terminal on the distal end from the relay before it splits from the wiring harness into the fuel pump branch and checked back at terminal #30 underhood. The same 700 K Ohm reading! I checked the proximal side of the connector (closer to the fuel pump relay) and found that the reading was erratic. I checked the distal end to the wire that I had soldered in just prior to the fuel tank harness and got .3 Ohms, a very solid reading for 15 feet of wire. At this point, I soldered in line some 12 Gauge wire from terminal # 30, fished it through the firewall by the harness entry point, and soldered it up to bypass connector 200. It works great now. The connector was beyond repair short of using epoxy to hold it in place. I prefer solder to any friction fit connector anytime. And the best part is that I don't have to let the gf use my truck anymore. And many thanks for the link to the haynes electrical diagrams.