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Well that was a waste of $200

T

Throttle

NAXJA Forum User
Location
A tree fort
Well I just spent most of my Saturday of the long weekend replacing my fuel pump just to find out that it WASN'T the culprit of my trouble starting.

Really it wasn't a waste of $200 because it has 130k on it and it saves me from leaving me stranded if the old one did eventually die.

So here's my plea to those out there that know 4.0L really good.

If I leave my truck sitting for more than an hour and go to try to start it, the first try it wont start, no matter how long I crank it for, second time I try to start it it does the same thing but some times sputters, third time, starts no problem
 
I know this isn't 4.0 related, but my 86 MJ with the 2.8 does the same thing. What I found works for my case is to turn the key to the run position, wait for all buzzers to stop, press the gas pedal 3-5 times, wait another second, then turn it over. Works for me 99.9% of the time.
 
beaterjeepjoe said:
I know this isn't 4.0 related, but my 86 MJ with the 2.8 does the same thing. What I found works for my case is to turn the key to the run position, wait for all buzzers to stop, press the gas pedal 3-5 times, wait another second, then turn it over. Works for me 99.9% of the time.
Click to expand...

probably because yours might be carburated. Pressing the gas pedal on a fuel injected vehicle wont do anything.

When I go to start it now, I have to turn the key to the accessory position, wait for the fuel pump to stop charging, then repeat 3 times, then start for it to start the first go.
 
i would check the inline fuel filter first if you already haven't changed it. the other thing i would suggest is testing the crank position sensor. they are notorious for going out on the 4.0. it is located on the top of the bellhousing. (automatic). my 87 Cherokee 4.0/AW4 did the same thing, and i also replaced the fuel pump and came to find out that it was the crank sensor the whole time,


good luck


:patriot:
 
what year is your XJ? like jk333 mentioned, it might be the crankshaft position sensor. for my 2001 XJ, this is what a bad "CPS" showed. fuel and voltage meters both inactive, fuel pump would not turn on, starter would spin, but engine wouldn't fire. if you left the key "on" for 10 seconds or so, the odometer says "NO BUS". and, a OBDII scanner will not be able to read anything from the computer.

if that matches what your XJ is doing... it's a pretty cheap sensor, but a PAIN to get to. you'll want to put a jack under the tcase and lower it a couple inches. you'll still need a lot of extensions for your rachet, I think I used almost 2 feet of extensions including a u-joint extension. two bolts holding it in place, upper drivers side.
 
check fuel pressure at rail. check engine codes may not throw cel light but still have codes. check relay connections pdb under hood. mine had a problem with starting totally random at first then more obvious then shut down on me on interstate then almost left me stranded after work. i got prepared to do a fuel pump job then isolated the problem to the relay connections. $0.00 dollar fix. that was 4 months ago. btw mines is a98. work smart, not on hard on random problems and search the forum for answers or atleast a trail to follow. i am proof positive of the SEARCH button. good luck. at least you know you have a new fuel pump and filter i presume.
 
What Year is it??? I have a 92 XJ 4.0L that never sees the road, but will die after wam-up if I don't use both feet, top speed is about 17mph in four high because the tranny won't come out of first gear. (auto) If it dies I have to to turn it off and back several times before it will fire.
 
The fact that it often happens when the xj sits, it almost sounds like a tempurature thing(or a fuel pressure thing, but it sounds like you are making up for that by letting the pump prime the system b4 starting). Depending on the year it MIGHT be a coil.
 
Last edited:
Might be a shot in the dark, but how about the coolant temp sensor?

Mine went through this thing last year where it gave me hell on starting from a cold start....no matter how long I "primed" it. It would sit there and crank, and crank, and crank some more. Once it finally fired it ran like poo for about 15 seconds (misfired) and would straighten out. Never did get around to replacing that sensor, as it turned warmer and I havent had that problem too much anymore.

In addition (and it's done this for two years now, and still does it), after I drive it anywhere, and wait about an hour or so like you said, it will take forever to start.
 
99XJSPORT06 said:
Might be a shot in the dark, but how about the coolant temp sensor?

Mine went through this thing last year where it gave me hell on starting from a cold start....no matter how long I "primed" it. It would sit there and crank, and crank, and crank some more. Once it finally fired it ran like poo for about 15 seconds (misfired) and would straighten out. Never did get around to replacing that sensor, as it turned warmer and I havent had that problem too much anymore.

In addition (and it's done this for two years now, and still does it), after I drive it anywhere, and wait about an hour or so like you said, it will take forever to start.
Click to expand...

Well I did just recently change the thermostat to a 180f thermostat, but I believe it may have been doing this before I replaced the thermostat..... not quite sure on that one tho....
 
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