Pez

1989 Cherokee,4.0, BA 10/5 😞,372k miles on original engine & tranny......ok, now 2 the problem.......stopped to eat the other day, maybe inside 30 minutes. Jump back in and try to start.....engine turns over fine but won't start. Try it 4 or 5 times same result. Get a ride to class....3 hrs later I get a ride back....starts up first try but starts idling about 3k (guessing as I only have idiot lights). Shut it down, immediately restart, idles fine,no issues.My initial guess was a fuel issue......hoping fuel filter(which I am changing today anyway) but wondering if it may be fuel pump starting to go?? Or electrical gremlin? Fuel pump is original as well...... Any insight or thoughts are welcome and appreciated.....

F1Addict

It is unlikely to be your fuel filter although if it hasn't been changed in a while, replacing it is part of semi-routine maintenance and not a bad idea. However, it's unlikely to cure your problems. For the no start, I would suspect your crank position sensor (CPS). They fail and random crank-no-starts are a typical first sign of that failure. The high idle could be the IAC but the more likely cause would be your throttle position sensor (TPS). I occasionally have the odd high idle on start up, usually 2000-2500 rpm but it settles back to normal within five second or so, so I haven't addressed it.

Check member Cruiser54's tips for checking the CPS and checking/adjusting your TPS.

cruiser54

Yes, and do Tips 1,3,4, and 5 while you're at it.

DFlintstone

Long before I knew anything about a Renix Jeep, I spray painted the CPS connector with white paint. Bonehead me somehow figured out that if you disconnect that, then plug it back in, the Jeep will start.

The reason I painted it white was so my elderly Mom could point at it and tell a helper, "my son said to try un/replugging that" Even recently with my Echlin putting out over .4 ACV, I've needed to do that a couple of times.

Follow Cruiesrs/F1's advice, but in the meantime maybe that will get you going.


My intermittent high idle likely was not the IAC it's self, but rather it's connector. Some CRC electrical contact cleaner, and on and off a number if times seems to have been the ticket there for me.

Pez

Thanks for all the leads �� My Saturday plan is going to be a checklist off of Cruisers pointers....LOTSA cleaning and testing......will let you all know if I find anything interesting. Thanks again.....

DFlintstone

Pete, what do you think. For white what I did was just loosen the nut on the grounds on the dipstick stud, spray it good with contact cleaner, work all the wires around a bit, re-spray, repeat, repeat. The result was that the surfaces that make contact got rubbed/riced. IIRC that gave me a goose egg for resistance from my engine side TPS ground.

cruiser54

Your TPS is grounded well then. Can you be confident your TCU and it's shift logic circuit are goose eggs also? No IP upgrade yet?

DFlintstone

OK, you got me there "IP"? My prostrate seems to be good enough for my age.

I have yet to do more checking, (not my prostrate!). Po of white has a cobbled TPS connector. I changed it to wire nuts, and again found no TPS ground on the trans side, through the TCU, (same as Brown), which shifts fine. I was only barely able to tweak white into spec. I would bet that I verified brown's TCU's ground is good. Mal-runctioning white's non functioning TPS ground could be a bad ground on the TCU.....

Any thoughts on the speed sensor? (and agreed, I should try another TPS).

You talking about my IP address? This is a stealth unit, I think....

cruiser54

Instrument Panel. Forget the trans side of the TPS and it's ground. Wire nuts are an improvement to cobbled up connectors of any other kind?

DFlintstone

Gottchya. I've got allot on my plate right now. The instrument panel ground can affect my shifting. Really?

And yes, I'd put a wire-nut right below solder, and a mile above those stupid crimped splices. Your house probably has hundreds of them handling way more current, with no Oxy-Guard, dielectric, or any grease. That crimp force even meets code for ground circuits in allot of states (I think). CA requires a special crimp for grounds, for safety (litigation), but about all power is handled with wire nuts. Ugly, but effective.

cruiser54

It can if the Power/Comfort switch is trying to ground through something else or vice versa!!!!!!

I wouldn't worry about it. I'm probably out of my gourd anyway. Carry on.

DFlintstone

Thanks, and yea, I suspected that is what you were getting at. I can swap stuff with Brown....I gotta suspect that TPS. It's much worse when it's hot.