89xjcherokeeguy

Hey everyone I'm a first timer looking for a little help or any info. I have a 1989 Cherokee with the 4.0. a week or two ago it shut off as i was driving. all electrical stayed on and it would crank like normal it just seemed like it wasn't getting any fuel. I changed the fuel filter (which was pretty dirty) and if ran good for a day. The next day driving down the road @ 60mph it turned off again. it would crank and start but when it would start it would rev to around 1500-2000rpm and die i tapped on the pump and filter and 20 min later it started and got me the rest of the way home. so now i have replaced the pump and filter and it ran good for a day again but when i went to start it this morning it did the same rev to 1500rpm and turn off all electrical still stays on and is unaffected. Im looking for any ideas i hate going to mechanics even more that im out of work right now. The only other idea I have is the fuel pressure regulator any thoughts?

x91evo

Well what we need to know is
Whats your fuel pressure? Does it stay steady, or go up and down?
Do you have a STRONG spark? You need a nice fat blueish spark
Is your compression good over all 6 cylinders? within 30psi of each other

cruiser54

Test your CPS:

Renix CPS Testing and Adjusting
　
　

Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.

Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.

The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.

Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.

You should get a reading of .5 AC volts.

If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.

Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.

A little trick for increasing the output of your CPS is to drill out the upper mounting hole to 3/8" from the stock 5/16", or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.



　

　

Revised 01-26-2013

Unplug and plug your CPS back in after tweaking the female barrels in the connector.