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XJ starts and then dies.

BrokenXJ

NAXJA Forum User
Location
Massachusetts
Jeep died in the driveway yesterday, starts right up and dies every time. Last year I had the thottlebody cleaned and rebuilt (new tps, ais, and egr). Any ideas?
 
Year?

If it has a fuel pump ballast resistor (the white ceramic thingie mounted inside the left fender next to the airbox on my '88), the resistor is bypassed when the key is turned to "START" and the fuel pump gets full 12 volts. When the key is released to the "RUN" position, power to the fuel pump is redirected through the ballast resistor. If the resistor is cracked, at that point the pump will stop and as soon as the engine has used what fuel it has in the rail, it will die.
 
A bad fuel pump relay can also cause this on a Renix 4.0 On these engines another relay provides power to the fuel pump while cranking and then the fuel pump relay provides the power when the ignition switch is in the RUN position. You didn't say what year or engine you have.
 
Well - he did mention EGR -- so if it's a 4.0 (and the shop didn't screw him) it's Renix Controlled (pre-HO) so the suggestions already posted have value - The User profile indicates an '88 so if it's not a 2.5L...

I especially like the Ballast resistor as the culprit! You can short-across that as a test; if the XJ stays alive, then you can stop looking.

On the relay, since all of the relays in the cluster (aft of the battery on the passenger side fenderwell) are the same part number a little "swapping" there can work for the other ...

If you have a tach - watch it -- how does it fall off -- is it a slow death (approximating what's happening to the engine) or does it drop like a rock only to have the engine stop tuning an instant later? (quick-drop, dead before engine can indicate ignition switch or other primary systems issues)


If you have a 2.5... ?
 
More info. Help!

My XJ is an 88'. I have a standard relay on the left fender wall. I took it off and one of the connectors was rotted off. I had to wait for today to get the relay from Jeep dealer.

I cleaned the connection and put the new relay on. The Jeep started and idled, so I shut it off. Later today I started it up and drove out of the driveway and it died, started the same symtoms!! It now starts right up and dies.

Why did it run for 50 yards! Should I have a ballis resistor also. My left fender well has a bunch of after market curse control stuff on, that may be hiding the ballis resistor.

I took out my voltage light and I am getting constant power on pin 30 of the relay, but am not getting power on pin 85 (orange), or 86(black) when the ignition is released.

Thanks in advance, Steve
 
PaulJ said:
The fuel pump relay is not on the left side. It's under the funny cover on the right side.

Correct.
 
Just jumper the ballast resistor to test. It isn't really necessary -- the '87s didn't use it. It was added in '88 to reduce the noise from the fuel pump by slowing it down a bit. You can jump it to see if it'll run and, if so, either bypass it or replace it, at your option.
 
Have you tried a new map. Mine was giving me intermittent problems like that. I took someones advise and changed all the sensors on my renix system. Mine runs great now.
 
It lives

I got it going this morning by jumpering the fuel ballast resistor.
BTW: The relay that I replaced on the left fender was the electric fan relay.
 
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