dastrius Posted yesterday at 07:08 PM Share Posted yesterday at 07:08 PM Hey all, happy Sunday! Got kind of an odd issue going on with my MJ and need some guidance. About a week ago I stopped at my local glass shop to have them reattach my rearview. As I was leaving, the truck had a real hard time starting. Crank crank crank - nothing. Did this once more and same result. Third time, it made a very odd kind of swallowing sound like it was gasping for air. For preface I have a CAI style cone filter in place given I didn't have a factory airbox at the time of the 4.0 swap. As it gasped for air, a puff of smoke came from out of the air filter. Thought it was odd but given I was on my lunch, I couldn't check it out right then and there. Let it sit for a minute and it turned right back on as normal and drove back to work. I had gotten gas the previous day and chalked it up to being bad gas. Truck was fine for about a week until 2 days ago. For the past month I've been fighting a real bad oil leak coming out of the back of the valve cover. Dripped down into the bell housing and would come off the bottom of that, and coated my whole undercarriage as I'd drive. I work for a Toyota Dealership and asked one of the techs to once over my work and see if he could spot where I was messing up with the valve cover leak. I let the truck run and it just randomly shut off when it got up to temp. Thought that was odd and went to turn it back on. Surprisingly, the motor did the whole 'gasp for air and blow smoke out the air filter' gag again. The tech was flabbergasted. Waited a few minutes and it turned right back on. Couple more minutes, turned right back off and did it again. This time, the tech caught that as it gasped for air, all of the pulleys and crank spun BACKWARDS and then stopped when I stopped cranking. We were stumped. It was getting late so we let it sit for a few and got it to run and limped it home. With the reasonable amount of time I looked at other people's issues on the forums, I figured maybe it'd be the CPS, given also that's the running joke of all renix issues. Measured it as per Cruiser54's guide on testing it, and both hot and cold it reads between .5v and 1v AC. Pulled it and cleaned off the tip thinking maybe it was gunked with oil and clutch material. Turned it on and shut off again once up to temp. It was getting late and I called it a night after redoing my VC gasket for the 5th time this month. (side note: I got it fixed!! 96+ VC with the OE metal grommets and a VC Gasket for a 95 4.0 ftw). This morning I walked out to the truck and tried to crank it over, and now it doesn't want to start at all. Tested CPS once again and is within spec. REM shows no codes at all. I'm stumped at this point, and any help is appreciated! Technical details: 86' MJ with a 4.0 Swap from an 88' XJ with a HO head on the block. Rebuilt about 5k miles ago. Thank you!! Link to comment Share on other sites More sharing options...
eaglescout526 Posted yesterday at 07:47 PM Share Posted yesterday at 07:47 PM Have you tested any of the other sensors? How new is the fuel pump? Grounds clean? How about the coil? I’ve heard of those getting heat soaked and being on the fritz when hot. Link to comment Share on other sites More sharing options...
dastrius Posted yesterday at 08:15 PM Author Share Posted yesterday at 08:15 PM Fuel pump is about 8 months old, but is a bit noisy. Checked fuel pressure and it holds at about 30psi while running. Grounds have all been refreshed and I relocated the fuel pump ground as per Cruiser. Haven't tested any other sensors just yet, wasn't sure where I should start looking. Sounds like ignition coil is next. Link to comment Share on other sites More sharing options...
eaglescout526 Posted yesterday at 08:56 PM Share Posted yesterday at 08:56 PM May not be the coil entirely but given it’s puffing smoke back out the intake makes me think it’s not firing and a bunch of gas vapors are just coming back out after the injectors firing. But I don’t know much about the 4.0 and it’s injection. Ironically I have the book on it. Link to comment Share on other sites More sharing options...
dastrius Posted 23 hours ago Author Share Posted 23 hours ago Just checked the coil, no spark coming from it. Checked the yellow wire leading into the ICM, it's getting 11.9 volts (read somewhere it's supposed to be a volt under battery voltage so that checks). Maybe ICM is dead? Leaning towards that or CPS. It's putting out .8v-1v AC which is a bit concerning given it's higher than typical range. Link to comment Share on other sites More sharing options...
eaglescout526 Posted 23 hours ago Share Posted 23 hours ago Could be. I one time had the contacts be dirty on the ICM that my XJ died on me and would restart. Thought it was the CPS and it wasn’t. Swapped the ICM entirely and fired up. Cleaned the contacts on the old ICM, put the coil on and fired right back up. So could be dirty contacts that could operate fine for a bit but then stop all together. Link to comment Share on other sites More sharing options...
dastrius Posted 20 hours ago Author Share Posted 20 hours ago Alright, good news! Went 45min away to the nearest O'Reilly's that had an ICM and grabbed it. Installed and she fired right up. Not 100% confident the truck won't do the whole gasp for air jig again but at least this is forward progress. Thank you again for the help! If I have any further issues with it I'll reply here. :) 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