omega_rugal Posted February 18, 2017 Share Posted February 18, 2017 after a week of working flawlessly my MJ just took a dump on me today, crank the engine, nothing, check the LPG lines, crank, nothing, test the ignition, no spark coming out the distribuitor... this happened to me before once but the problem solved by itself so i got no idea what happened, any ideas where to look first? Link to comment Share on other sites More sharing options...
Pete M Posted February 18, 2017 Share Posted February 18, 2017 crankshaft position sensor (CPS) is a common fail point. Link to comment Share on other sites More sharing options...
omega_rugal Posted February 19, 2017 Author Share Posted February 19, 2017 you think? like i said it happend before but solved itself after wiggling cable after cable until it ran, the ECU gets power as it drives the fuel pump (lpg evalve in this case) properly... is it getting a crank signal? is the sensor in the dizzy sending the right signal? damn too many variables... sounds like an afternoon of trial an error... Link to comment Share on other sites More sharing options...
Pete M Posted February 19, 2017 Share Posted February 19, 2017 the cps is a common random failure. if the ecu doesn't get a clean signal from the cps telling it where the engine is in its rotation, it won't fire the plugs. can be intermittent, sudden, and very frustrating. try wiggling the wires or cleaning the connector, and double check that the wires haven't cooked themselves on the exhaust. Link to comment Share on other sites More sharing options...
ParadiseMJ Posted February 19, 2017 Share Posted February 19, 2017 I don't think I'd be comfortable calling it good just by wiggling every cable each time I had an issue. Also, things that make your truck die all of a sudden don't usually solve themselves for very long. Some actual diagnoses might be in order here. Do you have a volt meter...a Digital Volt Meter (DMM) to test circuits? That said, what does it do when you turn the key? Nothing? Or does it try to start, but just won't catch? There are not that many variables. AKA when you turn the key does it turn the engine? Do you just get nothin' or does it crank and crank and crank, but doesn't fire, start? If it doesn't turn at all, I'd be looking at battery cables and connections, like take them off, shine them up and put them back on, securely and try again...don't just "feely" them and call it good...make SURE. If it turns and turns but doesn't start it's most likely that you CPS is toast, like Pete says. The CPS (CKPS) or Crank Position Sensor gets it signal from the flywheel/flex plate as it turns, if it's toast (which is what it sounds like) you'll get NO spark. Replacing it is a b**tch if you've never done it, but it's easy if you have done it a few times. 2 hours or 15 minutes. Depends on your experience level. Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 19, 2017 Share Posted February 19, 2017 What are you driving wtf?? How about editing your signature to show your rig details. At least HO or Renix. http://comancheclub.com/topic/51707-cc-members-edit-or-create-a-signature-to-describe-your-truck/ Link to comment Share on other sites More sharing options...
DirtyComanche Posted February 19, 2017 Share Posted February 19, 2017 What are you driving wtf?? How about editing your signature to show your rig details. At least HO or Renix. http://comancheclub.com/topic/51707-cc-members-edit-or-create-a-signature-to-describe-your-truck/ It's kinda neither. It's a Renix that the computer is only controlling the ignition and there's a demand based propane setup on it. I said it before, I'll say it again, I would put a HEI on it and be done. Throw some lighter springs in it so it advances hard and don't look back. Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 19, 2017 Share Posted February 19, 2017 That's nice. All that should be in the signature. Link to comment Share on other sites More sharing options...
DirtyComanche Posted February 19, 2017 Share Posted February 19, 2017 That's nice. Wow, you actually think something that not only has Renix parts on it, but isn't even chromed out, is actually nice! Way to see you're finally coming around on this stuff. Link to comment Share on other sites More sharing options...
omega_rugal Posted February 19, 2017 Author Share Posted February 19, 2017 fine i`ll fix the signature and yes it`s a renix, running on lpg and cranks for eternity without starting, i unplugged the dizzy lead and confirmed no spark is being sent... I would put a HEI on it and be done. i wish i had one right now, but is on the to-do list... i`m having enough with this mother@#$%ing renix... Link to comment Share on other sites More sharing options...
DirtyComanche Posted February 19, 2017 Share Posted February 19, 2017 Summit Racing sells a drop in one for $150. https://www.summitracing.com/int/parts/sum-850047/overview/make/jeep I'm going to order one for my J-truck at some point. Link to comment Share on other sites More sharing options...
omega_rugal Posted February 19, 2017 Author Share Posted February 19, 2017 $150? that`s a little high for an old, beaten up engine, for a freshl rebuilt one is well worth it... stil trying lo find a hackable GM dizzy... just checked the cps sensor and double check that the wires haven't cooked themselves on the exhaust. the cables are so cooked that became rock solid... oh i can see where this is going... Link to comment Share on other sites More sharing options...
omega_rugal Posted February 19, 2017 Author Share Posted February 19, 2017 bingo! the cable to the cps sensor was fried so i replaced the damaged part and now is up and running again... btw someone just offered me a 1990 XJ, 4.0 renix (damn) , AW4 part time 4x4, all black in exchange for my $#!&ty 1997 mercury sable wagon... should i? Link to comment Share on other sites More sharing options...
87MJTIM Posted February 19, 2017 Share Posted February 19, 2017 Yes Link to comment Share on other sites More sharing options...
Minuit Posted February 19, 2017 Share Posted February 19, 2017 Yes Link to comment Share on other sites More sharing options...
omega_rugal Posted February 20, 2017 Author Share Posted February 20, 2017 soo dissappointed the XJ looked great from outside, no a single dent, just old, washed out paint, fixable engine was a renix+aw4, running good but in desperate need of an oil change, not too bad but the interior, OMFG what the hell happend there? a complete mess: eaten up seats, windows don`t work, a door doesn.t even open, a window was kept open with a stick.. A STICK goddamn it, and dirty as @#$% i don`t even want to know what was in there, like someone barfed, pissed and took a dump there all at once... the mercury sable sucks but at least i won`t get AIDS while driving it... how can anyone drive that... Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 20, 2017 Share Posted February 20, 2017 soo dissappointed the XJ looked great from outside, no a single dent, just old, washed out paint, fixable engine was a renix+aw4, running good but in desperate need of an oil change, not too bad but the interior, OMFG what the hell happend there? a complete mess: eaten up seats, windows don`t work, a door doesn.t even open, a window was kept open with a stick.. A STICK goddamn it, and dirty as @#$% i don`t even want to know what was in there, like someone barfed, pissed and took a dump there all at once... the mercury sable sucks but at least i won`t get AIDS while driving it... how can anyone drive that... All this is off topic. No need for any more. Link to comment Share on other sites More sharing options...
Hippie66 Posted February 20, 2017 Share Posted February 20, 2017 bingo! the cable to the cps sensor was fried so i replaced the damaged part and now is up and running again... btw someone just offered me a 1990 XJ, 4.0 renix (damn) , AW4 part time 4x4, all black in exchange for my $#!&ty 1997 mercury sable wagon... should i? '90 XJ won't be Renix. Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 20, 2017 Share Posted February 20, 2017 '90 XJ won't be Renix. Really? What would it be then? Link to comment Share on other sites More sharing options...
Hippie66 Posted February 20, 2017 Share Posted February 20, 2017 '90 XJ won't be Renix. Really? What would it be then? XJ went to HO in '89. Link to comment Share on other sites More sharing options...
Hippie66 Posted February 20, 2017 Share Posted February 20, 2017 '90 XJ won't be Renix.Really? What would it be then?XJ went to HO in '89. Scratch that, I was wrong. Link to comment Share on other sites More sharing options...
omega_rugal Posted February 21, 2017 Author Share Posted February 21, 2017 yes, it`s a 90 XJ with renix, i saw it myself... Link to comment Share on other sites More sharing options...
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