Lately my 92 has developed a cute habit of the engine quitting while driving around town. I haven't been able to isolate the contributing factors as yet. It can happen when steady state cruising at 55mph. Today I was turning off a 50 mph road to a side street, it died as I was making the turn. Rolling on my street at 25mph, it died. Sitting in traffic, it died. This does happen after Ive driven around 20-30 minutes. So 12volt power is good, battery and alternator check out. when the engine dies I still have battery power as the radio and heater blower are still running. Shifting from D to N, I can get her started again. Sometimes it starts first try. Other times I have to cycle the ignition switch.

Ive reseated the IAC valve connector as well as the coil to dist wire and power to coil connectors. Since the 92 has limited troubleshooting codes there are no codes thrown to this point.

Anyone have experience with engine problems like this?

 

Try replacing the fuel filter, just a thought check fuel pressure at fuel rail.

 

I agree with Dusty in that fuel needs to be ruled out as one of the first things.....although there are certainly more than a few possibilities here.

Get a fuel pressure gauge. Many parts stores will rent them to you inexpensively if you don't have access to one, call around. With the engine running, it may not be conclusive but may yield a clue like being out of spec low. For a 92, you should have approximately 31 psi at idle. Then disconnect the vacuum line leading to the fuel pressure regulator and the fuel pressure should jump to approximately 39 psi. If there is any raw fuel in the vacuum line to the FPR, replace the FPR as it has a ruptured diaphragm. And yes, even just as a matter of course....replace your fuel filter. Easy to do on a 92, alongside the drivers side, easy to access and an inexpensive part.

Another wildcard here if fuel checks out is you can have random stalling because of a crankshaft position sensor starting to failure. May not set a check engine light. You mentioned that it happens after driving for 20-30 minutes...the crank sensor can absolutely suffer from "thermal" heat related failure, with engine heat screwing with this sensor. You can test the crank sensor but if engine runs when you test it, testing is likely to not be conclusive. Would have to catch it / test it right when it actually is failing which is tough to do. You could try carefully putting a bit of hairdryer heat to that sensor in the driveway and if the additional heat stalls the engine, then it's time to replace that sensor. If you end up replacing it, as hard as it is right now because of availability issues, try to find a genuine MOPAR crank sensor. Aftermarket crank sensors are hit and miss. With quite a bit of miss.

Good luck and keep us updated!

 

x2 on the crank sensor starting to fail. Typically does not throw a check engine code.

 

You guys made me think...I replaced the Crank Sensor about 4-5 years ago. I'm letting her cool down now and will play a heat gun on the CPS and the ignition pickup coil to see which one is being fussy.

 

When my CPS went started going in my '00 there were no codes either.
Just stall when reached operating temperature.
Thermal failure.
I suspected the CPS, asked here, many people agreed, and changed it out.
Turned out to be correct but was still a guess regardless.

 

Yeah I agree Ralph. Throwing parts is not a good method of trouble shooting. But as others have chimed in, this is a common failure with a characteristic symptom. Another part that is prone to cause the same symptom is the ignition pickup coil.

Anyhow a consideration for those following this thread is finding reasonable priced parts. Using the "Standard" brand part number I found the box stores at 75 bucks. Rock Auto....$35.00. I like to support our local businesses. But........

 

UPDATE - Replaced the CPS without success. I did find the Ballast Resistor (BR) was cooked and HOT. The engine idled for about 4 minutes then quit. Now the original BR is PN 8933000682 1.1 Ohm. The replacement is a "Standard" PN RU38 and measures 5.6 ohms. The engine does not like this part. And it too starts to get VERY HOT. Rockauto lists this same PN for my 4.0.

I've found a 0.8 and a 1.25 ohm parts.....just not sure about this.

Any suggestions as to where to start troubleshooting?

 

I don't have a '92 FSM but the '93 says:

"On XJ body, disconnect ballast resistor. Using an external ohmmeter, check resistance of ballast resistor. If resistance is more than 5 ohms, replace ballast resistor. Perform TEST VER-1. If resistance is less than 5 ohms, repair open in Dark Green/Orange wire. Perform TEST VER-1."

My '88, according to the FSM uses a 1 ohm resistor. I just verified by measuring mine.

Quadratec has them for $8.95. Oddly, it states for 87-93 XJ.

https://www.quadratec.com/p/crown-au...nd-comanche-mj

The Crown site shows it as 1.5 ohms.

https://www.crownautomotive.net/Ball.../33000682.html

 

Eliminate it and connect the two wires together. It was added afterwards to reduce the voltage to the fuel pump after the engine starts to make it quieter. Later years don't have them. As you noted, it does get hot since it's dissipating around 25-watts through the mounting bracket into the fender. Pretty common for the connectors to get corroded or for the ceramic to crack.

 

Not to be offensive, just hooking the wires together makes me a bit skeptical. Absorbing that much power? Whats the result? The fuel pump will just be noisy? I can deal with that.

I think I've found the answer from other XJ forums..OK

 

A little extra noise from the pump is all. The earlier years with the same exact pump didn't have the resistor and it was added to address noise complaints. I think 93 was the last year for it. The pump will run at the full 12-volts it gets while your cranking all the time instead of around 8 that the resistor knocks it down to. The fuel pump draws 4-5 amps through that resistor, which works out to 16-25 watts.

Since yours measures fine, you could just clean it up and reinstall it too. Usually when it's a problem, it's because the connections corroded causing more heat and the ceramic to crack and the resistor to open up inside.

 

'94 and later do not have it so "delete" is OK. It's bypassed at startup and full throttle. Just make sure you make a proper splice. You can always go back to the resistor if you want.

"Ballast Resistor (Cherokee)
A ballast resistor, located between fuel pump relay and the fuel pump, is used to reduce voltage to the fuel pump. This reduces fuel pump noise during operation. Ballast resistor is mounted on fender panel, next to washer fluid reservoir. When fuel pump relay is energized, voltage is supplied to fuel pump through the ballast resistor. During start and wide open throttle conditions, ballast resistor is by-passed and fuel pump receives its voltage from ballast resistor by-pass relay."

 

UPDATE ------- I ran a check then jumped the ballast. She ran for about 4-5 minutes and shutdown. It appears the fuel pump power is not a problem.

Tomorrow I watch the fuel pressure....

 

bump