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90 wagoneer starts but dies immediately

90woodyxj

NAXJA Forum User
Location
Sebastopol, CA
My 90xj will start but won't stay running. It shuts off immediately. Replaced the CPS (crankshaft position sensor) but it repeated the problem only a few days later. I also have an issue with extremelely high idle when it is running. Sometimes when it starts up it will "idle" at over 3000rpm. Any suggestions on either problem?
 
vacuum leak
loose intake manifold
stuck open IAC
dirty throttle body
throttle plate sticking.
 
Bad ignition switch (corroded inside so it heats up and disconnects) or cracked fuel pump resistor? Stuck open EGR valve?
 
Check the ballast resistor. On the inside of the driver's side fender. It's that grayish-white ceramic block with two wires to it. It reduces voltage to the fuel pump to cut down on noise. The start circuit bypasses it, so the fuel pump will run while you crank the engine, then when you release the key the power to the fuel pump gets cut off if the resistor is bad.

When you first turn on the key (before you crank the starter) does the fuel pump run for several seconds? If not, jumper the leads on the ballast resistor and try again.
 
Fuel pump is fine. Checked the EGR, that doesn't seem to be the problem either. Got a new MAP sensor off another jeep just for random hope's sake, didn't help. I'm thinkin' it may be a computer issue.
 
Don't jump to the computer too quick- it is about the last thing to go out. On my 1990 with 4.0 engine etc each time I had a high idle it was the TPS. I'm on the third since new. One of the things listed above is WAY more likley than the computer.
 
CHECK THE BALLAST RESISTOR!

Like Eagle said, the computer switches to a different circuit after startup. Which will cause exacty what your talking about.
 
Check for voltage on both sides of the ballast resistor, if there is nothing there, you need to check the fuel pump relay.

Look for the 4 relays all in a line next to the battery. If I remember correctly, the first one is for the electric fan, and the second one is for the fuel pump. Try switching them around (they just pull out) and starting the Jeep then.

If it stays running, then you need a new fuel pump relay.
 
I'll go with the TPS since he said it would idle high sometimes. That tells me that the engine is getting fuel fter start, but if the TPS is bad it'll either die or idle high.
 
okay, so it's not the TPS. Um, another symptom of the start up it has goin is if I keep the starter cranking i can keep it running. I can rev the engine and the whole bit. I know its murder on the starter, but it'll keep running if I do that. I'd check the ballast resistor now, but it's really cold outside and my jeep is way far down the driveway =P
 
well if you can keep it running with the key in start position then I would say it's a problem in the fuel pump circuit, most likely the resistor.
 
do NOT check the resistor with a meter, cause it will read good......just take a piece of wire and short across the terminals on the ends and start her up,,,,believe it or not, there are two conductors inside that resistor block...
 
do NOT check the resistor with a meter....it will check good. there are 2 conductors inside that block....just take a piece of wire and short across the end terminals of the resistor and start her up......
 
I'm bringing this thread up because I have the same problem that 90woodyxj has/had with his XJ. I can't see what the problem was, so I'm checking if someone can give me a hand.. I had this problem before, and a shop fix it but the guy didn't tell me what the problem was, he talked about a starting relay.... :( I don't have a clue were this starting relay is.
90woodyxj what did you do to fix this?, I have the exact same problem, the engine starts and when I loose the key it dies. If I hold the key in the cranking position the engine keep's running. Sometimes it starts right up, but sometimes it don't.
 
HotChiliRam said:
I'm bringing this thread up because I have the same problem that 90woodyxj has/had with his XJ. I can't see what the problem was, so I'm checking if someone can give me a hand.. I had this problem before, and a shop fix it but the guy didn't tell me what the problem was, he talked about a starting relay.... :( I don't have a clue were this starting relay is.
90woodyxj what did you do to fix this?, I have the exact same problem, the engine starts and when I loose the key it dies. If I hold the key in the cranking position the engine keep's running. Sometimes it starts right up, but sometimes it don't.

That sounds like a bad resistor wire for the ignition to me. (or the ceramic on the driver's side is gone TU) Other possibility is the ignition switch is worn out and not always making contact when you turn the key back to run. Try wiggling it to see if the motor catches.
 
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