Still no start, after a year.

OK guys, here we go again. i have posted and wrenched and cussed for a year now on my 91 XJ.

It started with this in Feb. 2011:



1991 XJ Sport 4.0L 4x4 AutoTrans



i am firmiliar with my truck and when it needs something critical to continue vehicles proper functions, i get it. i dont use, used parts that pertain to fuel spark or intake. situation as follows....


i install directv with my jeep....


Yesterday, i drove over 75 miles with no incident at highway speeds for the entire day. finish my last job, get in start, drove about a mile. while doing about 55mph, the engine stalls. i pull over turn the key, it starts, runs proper for a few seconds, then stalls. continued this way for 20 mins. start, stall, start, drive 100yds, stall. then i start it and when it tries to stall i feather the gas, and it recovers and just stumbles from time to time till i limp it home.

Today, it starts, idles, and drives fine. an hour into my day it dies again. i fumble with the distributor, to make sure everything is good.up until this point it has new (less than 3 month old) cap, rotor, ACCEL coil. i wiggle some of the old wires and it stumbles as if it is wanted to fire. with no luck i go to store and comeback with new wires and new distributor internal pick-up, a new fuel filter and Lucas inj cleaner (as i origianally assumed trash in fuel) fuel pump and ignition relays and fuses are fully functional. when key is turned, the fuel pump sounds as it always has. still with no results i had to get towed.

at this point this has just been an expensive form of troubleshooting, ie: replace stuff till it works.

i am out of bucks!! the next step that i can think of is Crank Position Sensor.

GURUS< ADVISE IF THE WRONG STEPS ARE BEING TAKEN.

air filter is fine
exhaust is absent of a catalytic converter
when the key is turned it no longer tries to start, but turns over STRONG
i have checked ecu grounds, battery connections and jumpers,MAP connections.

i dont know what else to do, but i feel confident that it is simple parts replacement. i am just afraid of it being something outside of my capabilities.

ANY AND ALL HELP IS APPRECIATED
................................................................................




Since i have replaced the fuel pump as well as PCM with 3 other XJ's. I gave up on trying to figure it out and sent it to the Jeep dealership for some results. after them wrenching on the thing for 3 1/2 months. they have since asked me to come pick it up. they had one answer, "Buy a new PCM" althought they said its most likely not the case. its just the only way to definitive way to rule it out. its got the required fuel pressure, its got spark, and of course...air...isnt the problem.


guys i am desperate, and i feel like i am having to make a life or death decision. after all the money put into it, it dosnt make sense to scrap it. not to mention that I absolutely would if it wasnt for the fact that i dont have new Jeep money right now. If it was just the no start i would feel better about making the decision to pull the plug. however it has a news trans, fully rebuilt front and a custom 8.8 rear, all new ignition, fuel and air systems, 5 brand new BFG KM2's and i am always looking to improve.


I am just worried that if factory trained technicians cant figure it out.....what in the world could it be. I am afraid it is the wiring harness, but jeep couldnt reinforce the thought. it is really frustrating. i would love to communicate with some of the most jeep savvy individuals. i am currently between jobs, so i am available all day. if any one wants to call me or lives in VA and wants to come by.....i would appreciate any assistance.:huh:




the list of replaced parts:

CPS
MAP sensor
distributor
plugs/wires/cap/rotor
fuel pump/filter
PCMx3
alternator
battery


used a volt meter to check:
TPS
coolant temp sensor


and after Jeep had it, they have checked all the routine items, as well as some unconventional testing im sure.

check the white resistor on the inner fender right by the brake booster I had mine come unhooked and acted just like tou are describing. Also air fuel and spark are all thats need to run make sure you have compression too. head gasket completely blown maybe.

compression is fine and i have checked for current to travel through the ceramic ballast. it is fine. im am fairly confident it is nothing mechanical. it must be information transfer somewhere. The dealership was able to get it to start a couple of times and it ran great, so timing, compression and air, fuel, spark are all there. they are unsure of why it will not continue to start. it is to the point where they will continue to check things at the rate of $50ish an hour. its beyond the free diagnostic. at that rate if i spent a $1000 for 20 hours, it still may do nothing for me. i know they have over 40 hours put into it already.

*There have been a number of threads of premature fail with that ACCEL coil. You have spark, but do you have "quality" spark? You need a strong, blue, snapping spark to fire up the engine. If you have an OEM coil, I'd put it on just to rule it out; only takes a few minutes.

*You mention compression is fine, but did you actually test all 6 cylinders with a gauge? No shortcuts. Looking for 120-150 psi, with no more than a 30 psi variation between cylinders

*You should be able to get a used PCM either at a salvage yard or on ebay. Those routes would be the least expensive.

X2 pm the coil. If it gets to hot the accel coils seem to fail. On the CPS even if new can fail and the plug if not getting a good connection can cause issues to. Alot of people either hard wire them in or change the plug out to a better plug. On the fuel pump ballast resister it may test good when cold but may have too much resistance when hot. It can be bypassed with no I'll effects to find out if that is causing the issue. The fuel pump may sound louder with the resister removed but this is normal.

Check and or clean all you grounds, don't forget the ground for the map sensor. People have had that 1 ground cause major issues, they usually end up adding a better ground just for that sensor. Recheck your alternator output. Should be close to 14.4v at idle. Never rely on the dash gauge though, lol. For the hell of it bring in the alternator to a parts store and have then check it. The better machines can tell you more then pass or fail. They can tell you voltage output, a/c ripple and more. All alternators create a little a/c voltage but if the alternator is letting to much by it can and will destroy a battery with out relizing it.

I have an 89 that had a "almost start/run for a few seconds issue" a few years ago. A pretty good mechanic shop had it for a week and tested/replaced all kinds of things with no good results. Eventually it was tracked down to the ignition switch under the steering wheel. It was fried/loose and was making and breaking all kinds of electical connections at it's own whim.

It will cost you nothing to pull the plastic under panel and drop the steering column for an inspection/adjustment. It is also a cheap part if it is crispy fried like mine was.

Also a pretty common failure on our old chariots.

Regards,
Tom

Join date of 2003 and only 3 posts? The Ultimate Lurker.

True forgot about the ignition switch. Had a few burn on me myself.

i will definitely check the ign switch. i had an ex's do that once. i tried a oem coil as well...no change. i have 3 PCM's 2 from my choice JY. the ALT is charging perfectly. during the 2-3 times that the jeep ran fine....it ran fine. compression isnt going to prevent the engine from even attempting to combust fuel. there is not even a sputter. i am very interested in the faulty CPS issue. it makes me want to go get another and swap it in to see if there is a change.

still, the fact that it has started and ran perfectly even once makes me think it is information not making its way to the computer. i have pulled some of the grounds like the one at the MAP, block-frame, head-frame, battery-frame, main fuse block. they seem tight, no corrosion, i even took a wire brush to the MAP ground.

it sounds like the first few days of getting the jeep back is going to be tedious trial and error. thanks guys.

First problem I see is getting it to start. Then once that problem is solved, we can work on the intermittent dying, as they may not be related.

I think your year still had a fuel pressure regulator on the front of the fuel rail. IF it is like Renix, there is a vacuum hose attached to it. If the FPR diaphragm leaks fuel into the vacuum line it quickly floods the engine causing a no start, and can kill the engine at idle. Check it first. Also check the ignition switch to make sure it is not adding to your grief. I had a new one die in just 4 months before I rewired some stuff on mine.

One or more fuel injectors may be leaking fuel, and flooding it. If you press the gas peddle while cranking, that tells the ECU to turn off the injectors, no fuel, and you get max air flow to dry out the flooded engine. If it starts cranking at WOT (try 20 seconds of cranking 2 or 3 times), you need to fined the source of the excess fuel next, FPR, or injectors leaking, or shorted injector ground wire, shorted to ground.

You also need to determine if the injectors are opening, or even getting power???? Many ways to do that, a stethoscope (to listen for clicking, open-close. Some people use a big screw driver, handle is the ear piece, and touch the injector with the metal end), or flashing noid light when current flows. The injectors fire when the ECU grounds the second wire. Have you checked to see if the Injectors are getting power?

WE have seen a rash of bad parts, new out of the box, including spark plugs, CPS, fuel pumps, TPS, IAC and so on. Just because a part is new, don't trust it. Get out an ohm/volt meter and test each sensor and each ground wire!!!!! Start looking for a bad wire connection with a meter at some point.

IF the IAC is stuck shut, trash in the throttle body IAC port or not getting power to open and let air flow, it can cause flooding and no start.

In summary, right now I would bet it is flooding, and staying flooded. Only takes a few seconds to flood one, to kill a good day!!!! Once flooded, it may take 1-20 seconds of cranking at WOT to un-flood it. Once flooded, you are wasting time, until you dry it out and fix the flooding issue.

Also, have you checked the OBD-I for codes?????????

Have you tested the fuel pressure at the fuel rail????? Too much or too little pressure????? Test it with a fuel gauge. There have been problems with new fuel pumps, low pressure....

fuel pressure is fine. i know that Jeep used "a" noid light, but i do not know if they used 6 of them. and dont know, inder what exact conditions they were used. i know that the jeep would fire up and run, for the first time in 6 months, and it ran....at that point they called me and said it was finished. they then pulled it to the parking lot and called me saying it was completed. never checking for the "on, off, on, off, on off." it started so they figured they figured it out.

i feel, and could be wrong, that if there was a flooding incident that there would be some sort of attempt at combustion. either before the flooding or after some of the fuel evaporating. there is either start, rarely. or no start. nothing in between of any kind. there isnt even the sputter of not enough fuel in the cylinder.

p.s. any of my comments are not shutting an idea down. just throwing some details out there. i definitely can be incorrect.
I came in and paid them for what they did, go to my jeep, try to start, no success. apparently, they can get it to stat once, then days of no start. they would go to it, no start, no start, no start......start, no start, no start, etc......they have not been able to duplicate the scenario.

now, i am very firmiliar with my jeep, and very mechanically inclined. not saying that i know it all, by any means. however, i know the terms of trial and error, and response and result.
i

They may not get enough old jeeps in to the dealership to know what they are doing anymore, and may not really care. They are there to service and support new Jeep sales (OBD-II tech), not keep 20 year old OBD-I vehicles running.

It does not take much to flood an engine, just a few seconds, and then you can crank all day long and you just flood it more, with no sign of life. Once you get past the maximum explosive limit of fuel / air concentration (ratio), you could toss a flame thrower at it and not ignite the fuel, figuratively speaking. Too much fuel, and you might as well try to ignite water.

I have had 3 serious non starters over the years. One was a leaking FPR. The other was a brand new CPS that was bad, but always tested good after it had already flooded the engine and I put the meter on to test the CPS, it would say, oh yes I am OK now, LOL, and the third was a bad Intake manifold air temperature sensor that let the engine flood quickly.