XJ Starts but wont run

I have an 89 XJ with 4.0 liter FI on which I replaced the fuel tank and installed a new manifold gasket. When I went to start it up after all the work I can get it to start but it wont continue to run. The fuel pressure is only about 20 psi and falls off to next to nothing and then it dies. It has a new fuel pump, new filter, new regulator. With the key ON the fuel pump voltage is only 6.6 volts. The wiring diagram I have doesnt show where the fuse is located for the fuel pump. Can someone point me to the cause? Thanks a lot.

tomking said:

I have an 89 XJ with 4.0 liter FI on which I replaced the fuel tank and installed a new manifold gasket. When I went to start it up after all the work I can get it to start but it wont continue to run. The fuel pressure is only about 20 psi and falls off to next to nothing and then it dies. It has a new fuel pump, new filter, new regulator. With the key ON the fuel pump voltage is only 6.6 volts. The wiring diagram I have doesnt show where the fuse is located for the fuel pump. Can someone point me to the cause? Thanks a lot.

Click to expand...

Ballast resistor, next to air filter box. Current flows through that when running but is bypassed for cranking/starting.

first suggestion... check for broken wire or pinched wire... the 6 volt is of course an issue... need to make sure that reading is correct.

check voltage at both sides of the ballast resistor on the driver side fender...

are you sure when wiring the pump the leads are not touching the bracket?

but... thinking still......

have you tried reversing the leads on the fuel pump wiring at the tank? If these are wired backward, they will run, but pressure will be non existant or low...

don't think your fuse would be an issue for now.

I have been on a business travel since makiing the posting and am not home yet. Yes I am sure of the 6.6 volts with the key on. Dont know what it is at cranking, cant stretch that far! I havent checked the ballast resistor yet as I didnt know what it was for. I am sure the pump rotation is correct as I had it wrong the first time. Had to remove pump and correct my miswiring inside the tank. I will check the ballast resistor upon returning home. Hopefully just a loose wire. Thanks.

Problem found! Thanks to your suggestions and directions I found the connection to the ballast resistor I had knocked loose with all the work I had done under the hood. Runs fine now. Thanks a lot for the help.