yxmj Posted July 1, 2014 Share Posted July 1, 2014 Hello Gents, Please keep in mind the vehicle in question is 2 hours from me and I am just working on figuring it out before I get there. The patient is a 1998 XJ 4L auto has been a strong runner. My daughter drove 2 hours one way to visit us camping.....on the return trip at about the 1.5 hour mark (having noticed no problems with the jeep or any alerts on the gages) it suddenly started to lose power and was not responding to here right foot. She pulled over, shut down and was unable to start.....had it towed home were my son was able to hook up my code reader......no codes shown. By telephone this AM I can hear the motor turning over strong and they have sent me picks of the code reader (display show 0) so last night my first thought was CPS.......................but with 0 on the display I am now thinking computer? I have (strangely enough never had a computer die on a 4 liter) Any thoughts suggestions or quick testes. My first suggestion was remove the battery cable until i re-contacted them..... :dunno: . :MJ 1: . Link to comment Share on other sites More sharing options...
shelbyluvv Posted July 1, 2014 Share Posted July 1, 2014 I'm saying CPS. Link to comment Share on other sites More sharing options...
yxmj Posted July 1, 2014 Author Share Posted July 1, 2014 I'm saying CPS. My thoughts too.....but the boy pulled a wire and put in a plug that had lots of spark when grounded..... I am driving home now and one thing that struck me was ......fuel pump???......sending them out now to see if they can hear the pump turn on or if there is presser at the fuel rail.. . :MJ 1: . Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 2, 2014 Share Posted July 2, 2014 Try cleaning up the CPS connector by spraying with some electrical contact cleaner in it. You might get lucky. Link to comment Share on other sites More sharing options...
Jeep Driver Posted July 2, 2014 Share Posted July 2, 2014 Fuel pump relay. Link to comment Share on other sites More sharing options...
yxmj Posted July 2, 2014 Author Share Posted July 2, 2014 Thanks for all the answers.....definetly fuel related as we were able to get it to fire by spraying fuel in the intake. Changed out the pump relay still no go.....will start working my way back from there.....hoping i do not need it but already have a feul pump on the bench.... :thumbsup: If you have any quick fuel pump tests or tricks please feel free to join in the convo............... Link to comment Share on other sites More sharing options...
shelbyluvv Posted July 2, 2014 Share Posted July 2, 2014 Jump the relay and see if you can hear the pump running. If not it is more than likely a dead pump. Mine just up and died a year ago and I still have not replaced it. The truck has been sitting in the garage ever since. Link to comment Share on other sites More sharing options...
yxmj Posted July 2, 2014 Author Share Posted July 2, 2014 Yes I already tried replacing the relay....and just jumping it with a wire.....nothing...........lucky for me I happen to have this in the shed Compleat tank with pump in it......will probebly be faster to do a quick switch.......clean out this tank first of course......i am online now trying to find out a quick bench test routine so i can be sure this one works befor I go through the trouble. :thumbsup: . :MJ 1: . Link to comment Share on other sites More sharing options...
mjben Posted July 2, 2014 Share Posted July 2, 2014 If everything else points to the fuel pump, be sure to check for power/ground loss in the wires just before the tank. Ideally, BEFORE DROPPING the tank... I once had a '98 (up country) XJ die on me in the middle of a trail run. No fuel. Decided it was the pump. Got pulled up hills, and then had a few crazy scary rides down with no power steering or brakes... Not fun. After a 60 mile flat tow home, she was in the driveway. Started the process of removing the tank skid and broke the first 2 bolts I turned. (Rusty Iowa Jeep originally) Got out the PB Blaster, gave em' all a good spray, and proceeded to break another bolt. Decided I'd better properly diagnose the problem before opening up a huge can of worms. Long story short, my test light revealed a broken power wire right where the harness starts going over the top of the tank. A simple heat shrink butt-connector got her right back on the road and could have avoided everything!!! :fs1: Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 2, 2014 Share Posted July 2, 2014 ^^^ Troubleshooting Electrical Problems 101. Verify power and return at the device before replacing the device. Link to comment Share on other sites More sharing options...
yxmj Posted July 2, 2014 Author Share Posted July 2, 2014 Yes thanks to you both....the test lights and the DMM are the first tools I reach for.....I am leaning towards the thought of a broken wire or bad ground as well......just because of the way it died.....suddenly while driving ........did not fade away or was not even intermittant....... just all at once Well enough speculation it is 2 pm here now....off work at 5......by 6 maybe 7 will have an answer I hope Link to comment Share on other sites More sharing options...
yxmj Posted July 7, 2014 Author Share Posted July 7, 2014 Finally had time to have an in depth look at the XJ. Since it is my daughter who went through the ordeal I guess she and the tow driver thought they were doing me a favor by putting the truck at the back of the yard no were near the shop….on a patch of raw earth….during 3 days of rain. I hoped I could solve it without hooking up the strap and dragging it inside. :thumbsup: She had let it sit with the key on so first order of business was to hook up the battery charger. First I went for the easy way….. That did not involve lying on the ground …..And went through the PDC with test light a DMM and confirmed that I was getting a pulse to throw the relay when the key was turned. Then bench yesterday the relay (to be safe I walked over to another 98 that was running and pulled its relay and popped it in….still nothing) I had bench tested the pump in the tank in the pic above with the battery charger …and finally in a break in the drizzle bit the bullet and crawled under the dead one and pulled apart the plug to the tank and hooked up the leads…noticeable humming sound….let it go 15 seconds….stood up turned the key….fired right up…best news all day …not the pump. Without taking as long as it took me to trouble shoot the harness (and cursing at everybody’s mother) finally was able to find the culprit….and a first time for me…. On an XJ the plug from the tank goes up through the driver’s side rear floorboard under the back seat (easy to get at) when it passes through the sheet metal it goes through a pre-formed (molded around the wires) rubber grommet……this is where my break was….totally hidden…no broken or frayed wire to slap me in the face but one that took 2 hours of searching to find in a spot you would think would be ok. Just a note for the MJ’s…..Harness is different the ground is at the back by the tail light….and the pump on MJ’s with a ballast resistor probably will not like the full 12 volts. Link to comment Share on other sites More sharing options...
mvusse Posted July 7, 2014 Share Posted July 7, 2014 87 4.0 MJ did not have the ballast resistor, and on the ones that do it is bypassed on start up (and during WOT), so testing the voltage across the pump you should still see (close to) full battery voltage unless the truck is running. Link to comment Share on other sites More sharing options...
yxmj Posted July 7, 2014 Author Share Posted July 7, 2014 87 4.0 MJ did not have the ballast resistor, and on the ones that do it is bypassed on start up (and during WOT), so testing the voltage across the pump you should still see (close to) full battery voltage unless the truck is running. ??????????????????????????????????????????? Link to comment Share on other sites More sharing options...
mvusse Posted July 8, 2014 Share Posted July 8, 2014 and the pump on MJ’s with a ballast resistor probably will not like the full 12 volts. The pump is the same for 87 (no ballast resistor) as in 88-90 (with the ballast resistor). The resistor was added due to customers complaining about the fuel pump being loud, meaning it must be bad. The resistor quiets it down some. But even on the 88 and later ones, that resistor is bypassed on start up and during wide open throttle operation allowing the pump to work at max capacity. The pump will like 12V (or even 14.4V from the alternator when the truck is running) just fine. Link to comment Share on other sites More sharing options...
yxmj Posted July 8, 2014 Author Share Posted July 8, 2014 and the pump on MJ’s with a ballast resistor probably will not like the full 12 volts. The pump is the same for 87 (no ballast resistor) as in 88-90 (with the ballast resistor). The resistor was added due to customers complaining about the fuel pump being loud, meaning it must be bad. The resistor quiets it down some. But even on the 88 and later ones, that resistor is bypassed on start up and during wide open throttle operation allowing the pump to work at max capacity. The pump will like 12V (or even 14.4V from the alternator when the truck is running) just fine. :thumbsup: Good to know....thanks for the clarification Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now