Zac_Lail

Hi I have an 88 XJ (Renix 4.0 I6) that was a bought a few months ago. The person I bought it from was driving and it died on him so he replaced the fuel pump thinking that was the problem, shortly after it died on him again so he sold it to me. It will crank all day but it wont start. There is no pressure at the fuel rail and I dont hear the pump buzzing when starting it. Also it has no keys and was wired with a push start Im guessing but it will still crank when turning the ignition cylinder. I dont think it would be the fuel pump considering it was just replaced. Does anybody have any ideas or suggestions that might help?

cruiser54

You can check for power at the fuel pump. Red wire, the biggest wire, at the fuel pump connector.

While cranking, you should have about 12 volts there.

Zac_Lail

Thanks Ill try doing that tomorrow. Also it looks like there is some melted tape or wire on the left wire that goes to the ballast resistor could that be a problem? Ill get a pic as soon as I can.

cruiser54

Yes, it could be an issue. Do you have a multimeter?

DFlintstone

Pretty sure the rear wire on the resistor goes directly to the pump. It's fine to bypass the resistor completely, ether for testing, or permanently. There is no need to go under the Jeep unless the pump doesn't run when that has power.

Zac_Lail

Yes I do have a multimeter. I will be checking every thing out today. Here's is that picture of the melted tape or wire I'm not sure what it is to be honest.

cruiser54

That's the ballast resistor. You should have battery voltage at both sides during cranking. Fix that wire.

Zac_Lail

Should I reconnect it to the resistor or just connect the wires after I fix it?

Zac_Lail

Also I know that it restricts the fuel pump while the vehicle is running so would the resistor being messed up like that be the cause of the fuel pump not getting fuel through the lines to the rail?

cruiser54

Yes, the resistor may be bad, but if that's the case, it would start and run for a few seconds.

Zac_Lail

OK I'll get under the jeep with a multimeter and test the wires going to the fuel pump.

Zac_Lail

Ok I was reading about 7 volts at the harness that connects to the fuel pump when starting. I hear no buzz from the fuel pump at all.

DFlintstone

Sounds too low to me, thinking of around 9 as a minimum. Front of the resistor gets about system voltage. 12 something sitting, and closer to 14 running. Rear of the resistor 9-10 ish I think. If that new pump is POS and drawing a bunch of current without running, that could result in low volts there.

The resistor is just to quiet the pump some. Some 87's don't even have them. Myself, I'd hook 12 volts to the rear wire, (past where it's boogered up), and see if the pump runs.

Cruiser knows better than me, but I myself would not suspect a problem with the wiring or the pump unless it didn't run with good power to that ugly wire there. (that clearly needs to be chopped off)

Zac_Lail

Thanks that was what I was thinking myself. As soon as I can I'll chop that wire and repair it. What's my next step from here. I still have no pressure at the fuel rail. Should I just got ahead and replace the fuel pump and hope that's the problem. Also would it be worth it to replace the o'rings that connect the fuel line to the fuel rail?

Zac_Lail

I just re-read your post and I think I will test the leads on the resistor sometime tomorrow. I had a family member looking at it with and he cut the o'ring/spacer clip off the fuel line without asking if I had the tool to remove it (which I do so I guess I have to track another one down because now it won't stay in the fuel rail (sigh).