FrankTheDog Posted August 14, 2013 Share Posted August 14, 2013 My wife's 92 XJ began giving us trouble a month ago. Then it just died and wouldn't start. I put in a newer battery, fuel pump, CPS and coil. I replaced the CPS because when I put a 4x4 aw4 in I didn't route the wire right and it melted. The coil I replaced because it had a huge crack in it. I diagnosed them by changing out with known good ones from my spare 92 MJ. I'm not sure the fuel pump needed changing as I changed that first. I put new fuel filters in too. Now a few weeks have gone by and now it's a little hard starting but runs well for ten or so miles but then it starts stumbling and back firing through the throttle body. I switched out the TPS and IAC with good working ones off the spare with same result. Today I swapped out the computer for one out of my 94 XJ and same result. When driving it when it first starts acting up it feels doggy between 3,000 and 4,000 rpm. Then it'll start to stumble and back fire. What do I check next? Link to comment Share on other sites More sharing options...
FrankTheDog Posted August 15, 2013 Author Share Posted August 15, 2013 Now it's even doing it when I first start it up. Link to comment Share on other sites More sharing options...
HOrnbrod Posted August 15, 2013 Share Posted August 15, 2013 Check for codes? I had similar symptoms on my 91 (except no backfire) when the distributor sync sensor was going bad. It showed up as a code 54. Link to comment Share on other sites More sharing options...
FrankTheDog Posted August 15, 2013 Author Share Posted August 15, 2013 No codes yet. I'll try again tomorrow. That's the next thing I'm going to try. Link to comment Share on other sites More sharing options...
FrankTheDog Posted August 19, 2013 Author Share Posted August 19, 2013 Turns out its the fuel pump. Tested it and it's only making 23 psi. That's with the vacuum on and off and with the return line clamped shut. Link to comment Share on other sites More sharing options...
HOrnbrod Posted August 19, 2013 Share Posted August 19, 2013 Hmmm. There's a lot of that going around lately........ Glad you found it. Link to comment Share on other sites More sharing options...
FrankTheDog Posted August 19, 2013 Author Share Posted August 19, 2013 Turns out it wasn't quite the fuel pump. The Bozo that installed it (me) didn't push the feed hose from the pump fully onto the hard line and it wouldn't let it fully pressurize. Pushed it all the way on and cranked down on the hose clamp and reinstalled the pump. Now it has 33psi running and 41 with the vacuum line off the regulator. I'm going to get myself a fuel pressure gauge for diagnosing these things in the future. Oh, and momma is happy now. Link to comment Share on other sites More sharing options...
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