Hamster

Well it was a PITA but, I replaced the crank position sensor and no joy, it still won't start.
I don't understand................it's getting good fuel pressure and a good strong spark.
One thing is for sure, it's just too damn cold outside to be troubleshooting this thing so, I had it towed to work and Monday morning, I'll have it put in the shop to let THEM figure it out.
Being an employee, I only pay 50% labor and parts are cost + 10% so, I can live with that. Even then, I can pay it out over time rather than having to have it all at once.

PDEM87

Just getting it up to room temp may get it to fire up. Even a good running vehicle can start hard when it's 11 degrees outside.

Hamster

After a bit of troubleshooting at work, we discovered that the ignition coil was only firing about half the time. Replaced the ignition coil and it fired right up. Test drove it around the parking lot a few times and it did great. When I headed home however, I hadn't made it 1/4 mile from the dealership when it spit and sputtered, then died..........almost like it wasn't getting enough fuel. When we tested the fuel pressure, it was reading between 31 and 35 psi so, I know that's good enough.
After coasting onto the shoulder, I tried starting it again and it fired right up. When I tried to rev the engine or put it in gear, it would die again. I started it up again and let it idle for a good 5 minutes.....put it in drive and it died again.
WTF!?!?!?

Roler

Did you end up getting a CPS from the dealer?

Hamster

Back in the shop today and after a bit of poking around (and a phone call to a full time Jeep mechanic), decided it is the pulse generator ring inside the distributor and found oil inside the distributor housing. This part is apparently not available by itself. However, a complete new (not rebuilt) distributor assembly that comes with the cap and rotor is only $65.00 my cost.

I was hoping to get it running today but, it started snowing a couple of hours ago and we've already got 2 inches so, they shut the dealership down and sent us all home.

That's just my luck, we haven't had a snow flake since I first bought the Jeep and now when we finally get some, it's down and I can't go play in it.

cruiser54

Hope it works for ya, but you can run a 4.0 Renix forever with a bad sync generator in the dizzy. Unplug it some time and start the Jeep.

PDEM87

Has anyone tested the new cps? Cruiser's cps test is very important. You should be around .5 volts ac as previously stated. Sometimes the top mounting hole needs opened up to acheive the needed voltage.

Hamster

Yes, the new sensor has been tested and it's good. The engine will start and run, it just won't stay running for very long. As long as the engine is cold, it will run just fine but once it warms up, it shuts down as if it suddenly loses the spark.

The fuel pressure has also been tested extensively............at idle with the vacuum hose connected and disconnected, also under a load. It's a little higher than the book says it should be but only by about 5 psi so, not enough to cause a problem.

One thing we did notice was, that just before the engine would shut down, the spark would change from blue to orange as if the ground was weak but, I've already done all the ground refreshing and we've thoroughly checked all the connections.

Roler

If this was observed to consistently happen before the engine would shut off, I'd think it holds a valuable clue....orange is a "weak spark" colour.
At least you now have a path to go down on...

Hamster

Yes.....it happens every time, about a second before it shuts down. The "Jeep" guy my co-worker talked to said he's had to change dozens of them over the years. The "Sync Generator Ring" on later models, is called a camshaft position sensor but, both serve basically the same purpose.

cruiser54

Absolutely not true. In the Renix, it has NOTHING to do with spark.

Hamster

Thanks to your advice, I did NOT replace the distributor. The XJ is running now but, I'm not exactly sure why. At one point, there was 3 pairs of hands + 1 hand from a guy who only has one, digging around under the hood.........wiggling wires and disconnecting, checking and reconnecting QD plugs. I'm thinking maybe it was one of the connectors on the ignition control module but again, not 100% sure. They were both spotless on the inside so the seals were definitely doing their jobs but, it was shortly after that, that it started sounding more even and wouldn't shut down again until I turned the key off.

I drove around the parking lot and down a side street several times (hitting every bumpy spot I could find to make sure whatever it was, didn't jar loose again) before finally heading home and it did just fine.

Now however, my "part time" light is staying on for some reason. I had the 4x4 computer unplugged during part of the testing because I'd removed the lower dash panel to get access to the ECU. I probably should have just unbolted it from the panel and left it plugged in but, I didn't. Anyway, while it was unplugged, the "part time" light came on. Even though I disconnected the battery before plugging it back in, it stays on now. It's not really a big deal I guess but, it's a bit annoying because it's bright yellow.

cruiser54

First off, TCU does not affect 4WD.

What you did was very possibly the solution. Why I wrote this:


I suggest unplugging EVERY electrical connection in the engine bay you can find, whether engine related or not, and spraying it out with a good electronics cleaner, visually inspecting the terminals making sure they haven’t retracted into the plastic holder, and then plugging it back together. There’s a critical 10-pin connector for the front lighting system located in front of the air cleaner and behind the left headlight assembly. Don’t miss that one. Also be sure that the connectors to the ballast resistor mounted near the air cleaner housing are clean and tight.

ALL of the relays should be removed, the terminals wire-brushed until shiny, and the receptacles sprayed out with contact cleaner. Then plug them back in. I do this on every Renix Jeep I purchase or work on for someone else.

Revised 07/23/2012

Hamster

Not the TCU, it never got unplugged. Maybe it's not called a 4x4 computer but, it was the only one unplugged when the PT light came on. It's on the right side of the vehicle and screwed to that lower trim panel that goes all the way across the bottom of the dash.

cruiser54

Sounds like the tCU that you're describing.