BizarroStormy Posted July 19, 2023 Share Posted July 19, 2023 So my Comanche left me stranded for the first time since I got it last week. Was running down the road to pickup lunch and it died after going about 2 miles. No sputtering, no struggling, it just quietly shutoff the engine. I did my normal figuring out why my jeep won't run routine, checked that no wires or hoses shook loose, and checked that fuel was in the rail. Fuel pressure seemed low to me, as not as much as normal shot out all over the place. It would turn over just fine, maybe sound like 1 cylinder would fire then just nothing. So I assumed it was low fuel pressure, bad pump or regulator, got a pressure gauge and tested it today after charging my battery. Pressure read 31 psi and it started right up. I don't think it was a bad battery because I cranked it a lot when I died, probably 2 or 3 minutes of cranking in total while trying to restart it on the side of the road. I couldn't really hear the pump priming on the side of the road but it was super loud with all the cars going by, but I can hear the pump now in my driveway. Also, I have done all of Cruiser's tips over the years, not to say something couldn't break or degrade in that time. I replaced the fuel pump when I got the truck in 2019, think it could be a dying pump? or am I missing something obvious? What should I check first? Really hate that I can't trust my truck now. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted July 19, 2023 Share Posted July 19, 2023 My vote would be dying pump. Very typical symptoms. Fuel pumps can just go out completely but I’ve noticed most that I’ve had go out in the last 10-15 years do so sporadically Link to comment Share on other sites More sharing options...
Ωhm Posted July 19, 2023 Share Posted July 19, 2023 1 hour ago, BizarroStormy said: Pressure read 31 psi and it started right up Is that 31psi with engine running or 31psi without engine running? Should read 39psi without engine running. Check vacuum hose on Fuel Pressure Regulator (FPR). Link to comment Share on other sites More sharing options...
BizarroStormy Posted July 19, 2023 Author Share Posted July 19, 2023 Just went out to check on the pressure, it goes to 30 when priming and stays there when running. But it just died again while idling, pressure is still good. So it must be something else. Link to comment Share on other sites More sharing options...
BizarroStormy Posted July 19, 2023 Author Share Posted July 19, 2023 Think I found my issue. I connected my REMII and it said it had a CPS fault. I put my multi-meter in the plug and I am getting .33v AC. According to Cruiser's site anything under .35 can cause a no-start. Link to comment Share on other sites More sharing options...
87MJTIM Posted July 20, 2023 Share Posted July 20, 2023 My vote is the CPS. I had the exact same condition many years ago. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted July 20, 2023 Share Posted July 20, 2023 Your idle fuel pressure sounds good. As mentioned above, 39psi should be the pressure with no vacuum attached/engine not running or WOT situations. Link to comment Share on other sites More sharing options...
BizarroStormy Posted July 20, 2023 Author Share Posted July 20, 2023 Got nowhere near 39, maybe 35 for a second. Noticed it was leaking down slowly after the prime. Just ordered a new pressure regulator, hopefully it isn't the pump as that would be super annoying to replace. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted July 21, 2023 Share Posted July 21, 2023 15 hours ago, BizarroStormy said: Got nowhere near 39, maybe 35 for a second. Noticed it was leaking down slowly after the prime. Just ordered a new pressure regulator, hopefully it isn't the pump as that would be super annoying to replace. The pump is very easy to replace finding a good replacement pump, on the other hand, can be more difficult Link to comment Share on other sites More sharing options...
Pete M Posted July 22, 2023 Share Posted July 22, 2023 might be that little rubber hose inside the tank. Link to comment Share on other sites More sharing options...
BizarroStormy Posted July 25, 2023 Author Share Posted July 25, 2023 Replaced my CPS, still no start. New one is worse than the one it replaced, only reads .25v while cranking. Think I got a dud or could my flex plate be defective? I had the trans off the engine last year and the plate looked fine other than some slightly damaged teeth. New pressure regulator seems to have helped, reading 35psi now. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted July 25, 2023 Share Posted July 25, 2023 On 7/20/2023 at 8:02 AM, ghetdjc320 said: My vote would be dying pump. Very typical symptoms. Fuel pumps can just go out completely but I’ve noticed most that I’ve had go out in the last 10-15 years do so sporadically Still sounds like bad fuel pump to me. Install your old cps back on. If the new one is giving you issues. Link to comment Share on other sites More sharing options...
BizarroStormy Posted July 27, 2023 Author Share Posted July 27, 2023 Second replacement CPS, this one reads .33v which is lower than what is should be. Still no start. Is there any way to adjust these so they are closer to the flex plate? Are all aftermarket CPS's garbage? Link to comment Share on other sites More sharing options...
MiNi Beast Posted July 28, 2023 Share Posted July 28, 2023 Not all. I would ensure cleaned at housing, and perhaps clean connection or could hard wire it as this has resolved some interminting issues before for myself and others. I would pull on the connection of cps while someone tries to start it up. Just jiggle the wire a bit to ensure its not that. Fuel, spark and air all at the right time starts everytime. Link to comment Share on other sites More sharing options...
GrandBoost98 Posted July 28, 2023 Share Posted July 28, 2023 12 hours ago, BizarroStormy said: Second replacement CPS, this one reads .33v which is lower than what is should be. Still no start. Is there any way to adjust these so they are closer to the flex plate? Are all aftermarket CPS's garbage? https://cruiser54.com/?p=50 I followed this tip and went from .3v to .5v Link to comment Share on other sites More sharing options...
acfortier Posted July 28, 2023 Share Posted July 28, 2023 2 hours ago, GrandBoost98 said: https://cruiser54.com/?p=50 I followed this tip and went from .3v to .5v @cruiser54 does this tip apply for HOs as well? Link to comment Share on other sites More sharing options...
GrandBoost98 Posted July 28, 2023 Share Posted July 28, 2023 That I'm not positive but I would venture to say yes. Youre just closing the gap between the CPS and flywheel so it produces a stronger signal. Hopefully someone else can confirm if it works for HOs or not Link to comment Share on other sites More sharing options...
Ωhm Posted July 29, 2023 Share Posted July 29, 2023 Yes. Any electromagnetic sensor (CPS) decrease in gap will increase AC voltage output, but to close can confuse it. Engine cranking or engine running speed (RPMs) has a greater effect on AC output. Increase RPMs increases AC output. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted July 31, 2023 Share Posted July 31, 2023 HO is a Hall effect sensor. Renix is VR. To the OP: do you have any spark? Have you checked fuel??? Link to comment Share on other sites More sharing options...
BizarroStormy Posted July 31, 2023 Author Share Posted July 31, 2023 Haven't checked spark, but I shouldn't be getting any if the CPS is not reading. I have been checking the voltage directly from the CPS unplugged so wiring is not the cause of the low voltage, I have replaced the wiring harness plug with a new one though. Have a NTK sensor coming in today, if that doesn't work I will try the boring out trick that I missed on Cruiser's site. Fuel is fine, 35lbs. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted July 31, 2023 Share Posted July 31, 2023 The ac voltage test on a variable reluctance sensor is somewhat subjective without a reference cranking rpm. The voltage is going to vary based on your cranking rpm and not all 4.0’s crank at the same speed as you well know. Battery voltage, ground and power cable condition and many other factors could greatly affect this reading. Try a fully charged battery with no spark plugs in the cylinders. My guess is that you’ll see a higher voltage. But again, try pulling out a plug and checking for spark before messing with the cps. You could get better sensor resolution when lessening the air gap, but it should still run just fine at the factory gap. Out of curiosity, did it start taking longer and longer to start recently? Link to comment Share on other sites More sharing options...
BizarroStormy Posted May 12 Author Share Posted May 12 So I finally fixed my issue after my truck sat for about 9 months. In the end it was the ignition control module. I figured that out after replacing the flex plate, crank position sensor, doing the cruiser crank position sensor mod to increase voltage, and the coil. Jeeps are fun. Link to comment Share on other sites More sharing options...
Gojira94 Posted May 12 Share Posted May 12 Which ICM did you get? Mine’s original and I’ve wondered who makes a decent quality replacement if I ever need one. Link to comment Share on other sites More sharing options...
BizarroStormy Posted May 12 Author Share Posted May 12 Got a Duralas one, I don't know how good it really is but my truck runs now. Looked identical to the original other than the potting material was translucent on the bottom. Link to comment Share on other sites More sharing options...
cruiser54 Posted May 12 Share Posted May 12 Glad to see it's fixed. I'm suspicious of new parts anymore. I keep a good used spare ICM/coil around. They rarely fail. I have to ask. Did you ever do the contact refreshing on that ICM before replacing it? 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