Over charging, and stalling out.

I give up. I don't have an ohm meter, so I can give you the resistance of any one sensor, or part of the harness but here's my problem/s...

First and most important the vehicle.... 1991 Jeep Cherokee 4.0L/AW4/NP231

New parts into this.... Rebuilt engine, ALL new sensors, new alternator, new ECU, new engine harness, all of my grounds have been cleaned throughout the whole truck. That's why it makes this really hard to troubleshoot (at least for me)


The problem... I'm overcharging quite a bit. It spikes to almost 19 volts at random, also a new thing is it randomly dies out now without warning. new CEL is set off either so I have no idea, I put another new alternator and another new ECU in it just in case that it was faulty from the factory, but my problem was still there.

Dude?

Justpunchit said:

I give up.I don't have an ohm meter, so I can give you the resistance of any one sensor, or part of the harness but here's my problem/s...

First and most important the vehicle.... 1991 Jeep Cherokee 4.0L/AW4/NP231

New parts into this.... Rebuilt engine, ALL new sensors, new alternator, new ECU, new engine harness, all of my grounds have been cleaned throughout the whole truck. That's why it makes this really hard to troubleshoot (at least for me)


The problem... I'm overcharging quite a bit. It spikes to almost 19 volts at random, also a new thing is it randomly dies out now without warning. new CEL is set off either so I have no idea, I put another new alternator and another new ECU in it just in case that it was faulty from the factory, but my problem was still there.

Click to expand...

Take a couple slow breaths and please clarify your points.

haha wow... sorry joe, I ment I CAN'T.... wrote the post from the garage on my phone, not the easiest to see what you type.

Justpunchit said:

haha wow... sorry joe, I ment I CAN'T.... wrote the post from the garage on my phone, not the easiest to see what you type.

Click to expand...

I hear you. Ok, you really need a multimeter to get anywhere. A code reader (better yet a scanner) can only take you so far--the codes/data can point you in a direction, but finding the real problem requires a multimeter to test sensors/wiring.

Sensor reference voltages are approximately 5.0 volts. The PCM is going to try and provide engine management based on data from sensors--if the reference voltage is off, then so is the output voltage--bingo, bango, nothing works right.

HF has $3 multimeters; the same thing will run you $10-$15 at your local parts emporium. Slightly nicer meters $20, and a NOS Sunpro/Actron multimeter with RPM function can be found on eBay for under $40.

The overcharging is likely the alternator, the PCM (controls charging), or a harness problem.

Here is an article on PCM controlled alternators: http://www.motor.com/article.asp?article_ID=1203 you have to scroll down a bit to get to the Chrysler section.

Voltage regulator is a possibility here, on a 91 that is in the computer.

Actron/Innova makes some great inexpensive meters. I was just in Walmart yesterday and they have the 3330 with autoranging for $25. A great meter at a great price. A cheaper Innova was only $12.

At those prices, nobody that works on their XJ HAS A good reason not to own and learn to use a meter. It is a mandatory tool and you don't need to be an engineer to learn the basics.