Hello all! New to this forum. I just picked up a 1990 XJ with 140k on it but non running. The PO replaced the fuel pump and filter because it just wouldn't start one day. So I put a new battery in it. Replaced the terminals. Also jumped the ballast resistor and cleaned the ground in the rear behind the spare tire. My problem is that the pump isn't kicking on but it did the first turn on with the new battery before it toasted the wire. and it keep burning and heating up the wire near the starter solenoid for the ballast resistor.

 

Hey Dustin, welcome to the forum! I might see if it's still shorted with the rear wire unplugged from the resistor/jump. Then you would know if the short is ahead or down from there. Likewise you could pull the second of the row of four relays and do the same test. Also disconnect at the tank in case the wires are shorting in there. (maybe start there and work forward). Trouble with wiring inside the tank DOES happen.

 

That's a great idea. I'll unplug the pigtail from the fuel pump and crank it again and see if it's still heating up and or burning through. I don't know where the "new" pump came from but the PO said he hardwired it and could hear it run that way. He thought it was the ECU or crank sensor. If it does then I guess I can rule out in tank grounding out and I'll move forward to the other side of the ballast resistor. I'll give it a shot tonight and see what happens. Thank you!

 

So just to make sure we are talking about that wire that is either red/orange looking connecting to the 2 green wires????

Not the yellow terminal that looks to be cut off or the blue one right?

 

If you jumped the ballist resistor, on the drivers side fender. That is why your wire is getting hot. Hook the ballist resister back up.

 

Ok so unplugging the ballast resistor still got the wire hot as well as plugging it back in and using a junkyard replacement. Still nothing. I did hear the fuel pump prime this time after having the battery disconnected all night. The red/pink wire is the one I am talking about.

 

Also unplugging the fuel pump relay didn't change it from heating up either. I did try a junkyard starter solenoid and nothing changed.

 

Ok so the last thing I tried was unhooking the pigtail at the fuel pump and it didn't heat up at all.. so I apparently must have a pump grounding out or seized?

 

Bingo!

 

Wrong. The resistor was added in the 87 year due to complaints of the pump being too noisy. It's OK to bypass/jump it. I prefer having mine in. Less wear on the pump I figure.

Little confused at that. That should have cut power to the pump.

Correct.

Fyi..The Fuel Pump gets power three different ways.

When wired stock..when you turn the ign. on, the ECU grounds the 85 terminal of the relay for a few seconds. This connects power from #30, (always powered by that fried, fusible link off your start relay), Connects that power from 30 to 87, across from there. 87 is power to the pump. This primes/pressurizes the rail.

Now, when you turn the key to crank, that terminal on the start relay powers the pump cranking, maybe bypassing the resistor, no matter there, it's powered while it's cranking by the starter relay.

NOW after it ether starts, or passes 300 RPM's and has completed two revs, the ECU, (from the CPS signal), will again ground 85 at the relay triggering it to continue passing power from 30 to 87.




These diagrams as well as links to Cruisers stuff are in the link in my sig.

It's power from you ign at 86, when 87 is grounded that energies a little electromagnet in the relay. (here the ECU grounds it.--- Start relay is grounded by the NSS, different relay, same principal) That then closes points that shoot the (fused link power) from 30, up and out 87. The SPDT relay will connect power to 87a at rest, then switch it to 87 when 86 has power and 85 is grounded. (I use these "cube", Single Pole Double Throw relays for all sorts of things) Their coil uses very little current.

 

Maybe the rear wire is double, and getting power from the start relay while cranking.

 

Ok latest update is.. I warrantied out the fuel pump. It's a Delphi from autozone. The in tank ground was really loose so since it was out I replaced it. Now when cranking you can really hear the pump it's loud and the ballast wire isn't burning or heating up so making progress.. Still not firing over though. There is a leak from the fuel rail picture attached any more advice from here. I also swapped the relays around with some from a junkyard and still no fire.

 

Note from DJ
Is this where your fuel leak is?

 

Make sure you have good fuel in the tank (at least 1/4 tank) and that the battery is fully charged. Renix are sensitive to the engine speed (CPS counts the teeth that pass by). If the CPS is bad, it won't start but I'd hate to go in that direction right away. DFlintstone has a link to Cruiser's tips on his signature.
The leak on the fuel rail is an issue but it won't matter to the ECU as far as firing the plugs. You have a new pump and new fuel filter and hear the prime. It would be good to check the pressure on the fuel rail with a gauge but you could assume for now there's enough fuel (since it's leaking out!).
The Cruiser Tips should be followed to make sure the obvious and not so obvious have been ruled out.
If you bought the Jeep in a non-running condition, I would want to check the CPS output voltage before you get too far in. Could be a bad CPS right from the get-go.

 

http://cruiser54.com/?p=50 for the CPS test.

BTW, good job so far.