jlind871

Hi,

So I'm out of my league on car things.

My 1990 Jeep XJ does not start. 4.0L automatic

The conditions that lead up to the no-start were:
Started car normally in drive way, drove out the dirt path up to the road, powered into a turn and then it conked out.
I was able to restart the jeep right there, but it conked out again. I was able to start it up again three times.
Engine would unceremoniously and instantly die whenever it revved up to shift gears.

I got a smell I had never smelled from my jeep before after it died for the third time and I decided to let it cool down.
It smelled like gas, or something burning, I'm not sure.

I pushed and pulled it to the local shop.
They were kind enough to provide free diagnostics as far as fuel pressure (which was good), spark (no spark signal, but spark from coil), and EGR, PCV valves which they said were good.
But since the problem is electrical and this is a Renix, they advised against requesting more work because they'd charge $95 an hour to fish through a 30-year old engine bay to find a bad wire.
(Not their exact words, but I'm filling in the gaps with them having two vehicles stuck in the garage with seized suspensions that they did not have time to work on it at that moment)

So I towed it home, and we cleaned up the engine bay a little bit. I also disconnected the battery and did the little ritual one does to reset the PCM, then connected a tender to the battery for the night.
The next day, a friend went out there to start it, and it started! For about 10 seconds. Then it died again. He says it just conked out on its own, but I have to wonder if he revved it up. I was at work...

So as to where we're at with this:
It cranks, but unevenly. Every other crank drags. Is that normal? Any other time it'd only do that on a low battery.
After it died the driveway, the sound it made when cranking changed. Some element of the sound is removed. You can hear something is wrong. Would the spark plugs / coil be audible?
The fuel pump priming is audible.
When cranking, you can smell gas.
My friend has pulled the sparkies and said there is spark, but also at some other time said there was no spark at No.1 cylinder. Confusing...
With the key in ON, you can shift gears, and you can also shift the transfer case. All the lights work.

It's strange. I tried to start it a couple more times between the third death and the final death.
In these cases, you could hear and feel at least one of the cylinders firing. It was firing just not enough to keep going.

What we've done:
Cleaned the distributor (seems alright)
Replaced the fuel filter
Reset PCM

Mainly I'm just confused. Why with no other indication of failure would this happen? It didn't burn oil, it didn't misfire, it didn't knock, it didn't slip gears.
I guess all that is totally unrelated considering the problem is electrical. But is it? I don't know...
The only other problem is with the light switch, and that can probably just be cleaned.

Sig220

I would be checking the crankshaft position sensor (CPS). When it goes out, you won't be able to go anywhere if it does start.

Find you a FSM for that model year and I am sure they have tests to confirm the function/non function of the CPS.

As always on electrical problems, make sure your grounds are shiny and clean, take them off and make sure!

Good Luck!

jlind871

I was out there earlier today looking for the CPS. I can't even see it, it's supposed to be on the bell housing right?
I have a service manual, actually, guess I'll see what it says about it...

jlind871

Okay, sorry for the double-post. I was able to identify the CPS and checked the resistance across the pins.
The service manual say it should be 200 +/- 75 on a _hot_ engine. It's reading 220 on a cold engine.
I don't know what to say about that, but it should still be ok.

I'll check the ground studs tomorrow. I'm certain they are dirty.

djgrayxj

Note from DJ

I don’t know if you if you are still looking help with your no start problem or not; but if you are I’m going to offer you some simple thing to check that might clear up some of the things I have questions about your problem.

1. Check the dirty condition of your air filter; if it is very dirty this contributes to what maybe a flooding problem.

2. You stated that sometimes you have spark then other times no spark. If you have a tachometer included with your gage cluster you will notice a slight bouncing movement of the needle while cranking if the coil is getting a signal to fire a sparkplug; this is what is the first thing I look for if my 88 fails to start.

Now here is a simple test for under charged or a weak battery; if this is apparent the starter will be consume so much of the voltage available the coil will be producing a weak spark or no spark at all.

3. Take your voltage meter an meatier the static voltage of the battery; now getting into your XJ leave the door open so you can observe the interior lights, next turn on your headlights to the bright sitting and now try to start your Jeep; if your interior light becomes very dim or goes out completely you have a weak battery or bad battery cables or pore connections.

Remove the battery and take it to work with you and drop it off at your favorite parts store and have them no a load test on it. This test will element on of the possible problems.

Now here is a link to a lot of very correct information regarding the Renix year Jeeps.

Renix Tips by cruiser54 link on 10-1-20

http://cruiser54.com/

jlind871

Thanks a lot for the tips mate. I have put a new filter on.
I probably won't be able to get back to it till next week, it was storming today so I decided to just let it be.

As far as the battery goes, at _this_ point it probably is dead, because of the rapid drain-charge. Mostly I'm relying on a tender / battery jumper to try and start it.
I'll have to probe it and check the tach.

djgrayxj

Note from DJ

In reading over the information you have provided in more detail and it appears your Jeep has a history of the battery going dead.

Is this happening because of just sitting with not being started or because prolonged attempt to start?

jlind871

Well, first, yes this jeep does have a history of the battery dying.
In the first case, it was due to sitting 1-2 weeks at a time between being driven.
After a time of that though, it would kill batteries even if regularly driven.
We replaced the alternator and the master power relay about 3 years ago, that problem was fixed.
So this battery is about 3 years old then, and it has been drained to just about nothing a couple of times from cold start attempts, and one other time where I foolishly forgot to disconnect the battery whilst I took out the interior to do some work on the rusty floor.
A bad battery wouldn't cause it to conk out on the road, though.

That's the first issue: it conked out, then would not start.
I also jumpered it and tried to start, the tachometer did not move.
Maybe just some rogue rubbed out wire or bad relay...

Though this Jeep has for about 7 years needed extended cranking before it would start. Not too out of the ordinary, and it would start immediately once warm.
Anyway, that battery is probably well and truly dead at this point, having been drained from so much cranking.

djgrayxj

Note from DJ

Here is more information on Battery State of Charge or SOC with Colored Chart

Note: For longer battery life, batteries should remain in the green zone (40% or more SOC). Occasional dips into the yellow may not be harmful, but continual discharges to those levels will shorten battery life considerably. Generally speaking, the less you discharge the battery before recharge, the longer the battery will last. Most alternative-energy systems are designed to keep the battery bank at least 50% or higher.

Note: The 100% voltage is NOT the recommended charging voltage (which will be higher and multi-stage). See your battery manufacturer recommendations regarding charging.

STATE OF CHARGE CHART

jlind871

Well, I already got a new battery. (Old one was at 9.8V, definitely dead) I have a new fuel pump on hand.
I tried cranking it a couple times and "tested" the pressure at the valve on the injector rail. It just dribbled out. If it's supposed to be at 40 PSI, there is no way that pitiful dribble is enough pressure.
That would also explain the 10-second run, and then death. A bunch of priming and the failing electrical system / pump would build up enough pressure to run for a bit, but not long enough.
In the mean time, I'll be poking at and cleaning the grounds in the engine compartment. For a long time now, the voltage gauge on the dash has leaned low, that must be an indication of bad ground.
I also need to replace the headlamp switch as it's clearly shorting or arcing, it makes a buzzing sound and the headlights go out. That can't be good for the electrical system considering it has no relay.

Fun thing, my friend took off the distributor cap to take a look at it. Dunno how, but he forgot to put the rotor back in. That's why there was no tach movement. There is tach movement now.

cruiser54

check and see if the wires are loose on the ballast resistor.

You can actually bypass the resistor and see what happens.

cruiser54

Here's a thought.

Ever gone to my website and completed Tips 1,3,4, and 5?

djgrayxj

Note from DJ

When you remove your old fuel pump before you throw it away pull on the hoses that are a part of the pump.

The reasoning for this is the Ethanol gas we now haft to burn will cause the older hoses to become soft and it have been found that in some cases the hoses have moved enough that they leak at the connections; If this has happened to yours that will explain your loss of pressure.

And don’t forget to let us know if the problem was solved.
I hope the news is good.
And follow cruiser54 tips.

jlind871

I've got more diagnosis to do.
I've pulled up every relay I could find in the engine bay and verified the contacts were cleaned and sprayed them with contact cleaner. (That tends to be done on this jeep once every 2-3 years...)
Every plug I pulled open was shiny clean.

The behavior now seems to be:
Cranks, gets fuel, fires once and then STOPS sending spark pulse and STOPS sending fuel. (IMMEDIATE death)
I actually thought I heard the pump prime before ignition. Actually I'm hearing the brake pump. The fuel pump does not prime before ignition. Tried swapping relays, that doesn't change, right now I'm assuming that this jeep has never done that as long as I've known it. I do need to find the exact contacts to jump to run the pump constantly, just out of curiosity. I'm assuming there is no fuel pressure sensor that will stop ignition pulse if pressure is too low.
Bypassed ballast resistor. No affect, didn't think there would be. Its resistance was awfully high at 4 Ohms, permanently ditching it.

The one ground I can't reach right now is the one behind the dipstick. Obviously, that's the most important ground of all of them-- I have to get to it somehow tomorrow.
I also need to do more diagnosis at the pump itself. The line is definitely soft, but I don't think its a fuel issue anymore. I can't smell any gas down there after starting attempts. I tried starting fluid tonight, the same thing happened: Fires once (well with the starting fluid it fired twice but w/e) and then stops sending pulse. (No tach movement)

So, what else can I look at? What goes on in the ASD circuit, again? I've also got the headlight switch to replace but that's besides the point.
The engine ceasing to send ignition pulse as soon as it fires seems suspicious. Like that would be something very specific. Distributor...?

Another Q, what should be plugged in to the coil module? It has three plugs, but only two are occupied: The radiator-side 3-prong plug, and the center 2-prong plug but that particular plug has only 1 wire populated.

cruiser54

Done Tip 4?