Automotive → 1996 Grand Cherokee - No Start

I've had the in-tank filter clog on both a Cherokee and a Ram. Oddly enough, the pump is open at the top so everything is fine with more than a 1/2 tank of gas. Fuel pressure is still OK but flow is restricted. The pump holds enough gas that seeps through the clogged filter so it can take a bit to act up after the vehicle has been sitting.

Just a thought but since nothing else has worked, how full is the tank?

Correct for this vehicle, yes. The specified fuel pressure is 49psi +/- 2psi. I am reading around 48. That is, when I can get it to idle.Base timing is not adjustable. Using the procedure for installation of a new distributor, the base timing is correct. (There is a hole in the distributor body, and in the shutter wheel. When the motor is brought to TDC on #1, this holes should line up, and do.)That was my thought. Me and a friend checked the wiring from the CKP sensor to the PCM, and the CMP to the PCM. Both check fine, with good continuity back to the appropriate pins. We even pulled the harness apart to follow the wires back, moving the wires while hooked to the multimeter. Good connection.

The PCM was replaced due to the vehicle just shutting down at random, and being able to (usually) start it right back up, after cycling the key. When it died like this, you couldn't communicate with the PCM. After you cycled the key, you could.

A screw up on my part was getting a cheaper PCM from a place down in Miami. They have a lifetime warranty on their PCM's, but it's no good when I can't rely on the quality of their work. The last PCM they sent me isn't even reporting as the right part #!

I have access to another 96 Jeep Grand Cherokee, exactly like mine. It runs good, but the trans is shot. The owner of the Jeep is going to let me use it as a test bed to test my PCM.

Going to try to get back after it this weekend. If I put the PCM in the other Jeep and it runs, then my only recourse at this point is to pull the engine harness, and go over it wire by wire. It's really not that hard to pull the harness, just time consuming to make sure everything comes out in one piece.

Check the sensor resistance at the ECM pins. Check that tranny is bolted up tight and maybe check that the flexplate isn't cracked and wobbling.

I wonder if the 96 has the same stupid ECM ground wire setup as 93 ZJ. On the 93, all of the ECM grounds converge into a single wire that run back to the battery ground. Mine got damaged somewhere along the way (probably when I had the battery replaced). The engine would die if I hit a bump like I turned the key off, with no codes set. Would start up right away or after I towed it home. Drove me crazy for a few weeks until it finally stayed dead and I found it while checking grounds at the ECM.

I thought about grounding issues, and cleaned up the grounds where it bolts to the coil bracket, but didn't really check them back to the PCM. Time to break out the pinout sheets and the multimeter...

Well, I got out to the Jeep today, and we checked out the grounds to the PCM. They were all good. So, we were checking that the PCM was putting out the 5vdc signal for the sensors. Check... it's putting out 5.17V.

Well, we decided to investigate the distributor closer, because it has been a source of problems before. When we removed the cap, we noticed that the shutter wheel had rub marks on it, where something was dragging on it. Pull the cam sensor out, and looked closer at it, comparing to a new one (that supposedly doesn't work) and we saw a clean wear mark in the sensor, where the shutter wheel was hitting it. Since you cannot adjust this wheel, we condemned the distributor (a new one was only $60). Pulled the old distributor, and noticed the hold down tab was broke off. The only thing holding the distributor down was the anti-rotation clip on top of the hold down tab. We also noticed the distributor gear looks a little chewed up. Shining a light down inside the block, the cam gear looked okay.

Replaced the distributor, and somehow, we managed to pinch the damn Cam Position Sensor harness. If you push it together, it will run fine. If not, it won't even TRY to start.

So, now I am looking to replace the connector. Standard Motor Products makes one, S-1838, $30 from RockAuto. Going to order it on Wednesday, and solder it into the harness. Hopefully, this fixes the engine problem. I'm sending the PCM back to be inspected since I am not getting any oil pressure reference. The gauges worked with the previous PCM.

Don't take this the wrong way, but this has taken quite a long time to diagnose and fix; even though it officially isn't fixed yet, the issue sounds plausible,

I hope you are aware that the approach you took was incredibly flawed and increased the difficulty in pinpointing the root cause.

I am sure this had to be an incredibly frustrating exercise for you, but unfortunately you tried to use a shotgun approach to the problem and were trying to guess your way to the cause. It rarely works that way, which is why I suggested diagnostics to isolate it. Throwing parts at a problem is a poor way to diagnose a vehicle.

Hadn't you had the distributor cap off before? Weren't you checking for play in the distributor shaft? Unfortunately you were right there. Were this a shop environment the customer would have probably wanted to flip their lid.

Anyway, back to the distributor: I'd be concerned about the distributor gear being damaged. I'd like to see a picture of that. Perhaps there is a lot of end play in the camshaft of the bearings for the cam weren't replaced or another issue caused the wear on the gear. Better to know now before blowing another distributor away.

It took as long as it did due to the fact that I simply didn't have the time to work on it.

The PCM was throwing a loss of CKP or CMP reference to PCM. I suspected the CKP, since when it was originally installed, they did not use the spacer card. Of course I didn't bother to check the old sensor until AFTER it was swapped out. Oh well. My loss. Now I have a spare CKP.

As for the cap, I have had it off... multiple times. Most of the time, the shutter wheel was facing away from me, where I did not see the marks on it. I've also noticed the notch in the sensor, but didn't put two and two together. It wasn't until a friend of mine came over to assist me that HE noticed the marks.

When I had this block tanked, I had it line bored, and new cam bearings installed. Also had the cylinders honed as well (they did not need to be bored). The only thing I can think of, besides the cam not being installed right, is that either the distributor itself was junk, or the gear on the cam is eating the distributor gear. (I seem to remember reading about a certain cam gear that was harder than the distributor gear, and it would eat the gear.) The cam is a Comp Cams shaft that was designed for this particular application. (The part # escapes me right now.)

The old distributor was a new unit from Cardone, that I purchased from Rock Auto. It has a lifetime warranty. Right out of the box, the distributor cap was broken. Not a big deal at the time. Then the rotor failed a few months later.

I have the old distributor out in the Jeep. I will go out here in a bit and get a picture...

Pictures as promised...

I have to say, that distributor sure looks older than 2 years old. If the cam distributor drive gear is hardened it can cause wear so the recommended gear would be a "bronze" gear for the distributor. If you put a high volume oil pump in it without enlarging oil passages, that can accelerate gear wear.

Oil pump is just a stock replacement.

The distributor is a little over two years old. Closer to three. It was bought in Feb of 2012, but not installed until March of 2012.

Not sure of the gear on the cam. Going to look it up when I get time. If it is hardened, then I'm gonna have to find a bronze gear for it.

Replaced the cam sensor plug on the harness. I can use wire nuts, right?

Just kidding. I do what I normally do for harness repairs, good mechanical connection, solder, epoxy filled heat shrink.

There is a replacement plug available from Standard Motor Products, but it seems to be either on back order, or an astronomical price. I went up to the local pick-a-part yard, and grabbed one.

Seems to be running fine right now. Took it for a test drive today, and didn't have any issues.

Here's hoping *that* issue is fixed. Now I need to address the distributor gear issue. IIRC, there is a spring and button at the head of the camshaft that rides against the timing cover to pre-load the cam. I don't remember off the top of my head is there is a cam retainer plate or not. (Just checked the FSM, there isn't one.) If this pin or spring has broken, then my cam is walking, and that's probably my problem... Problem is the only way to see if it is the spring/pin, is to pull the front of the motor apart. Or pull the distributor and use a small pry bar to check the play in the cam.

Cam end play was an issue on Rover vehicles for a while
; a 1-2 degree forward ramp to keep the cam from moving rearward was developed. Even so, the cam would wear a bit and knock. While not an issue that caused undesirable operation, there was usually a knocking noise that customers complained about. Luckily on Serpentine belt engines, we could just remove the timing cover and there was a cam button that could be installed to correct this. The better fix was to install a GM cam button and spring, but it was rarely done.

Get that fixed and your cam/distributor gear problems are history. I'd love to see that.