1989 cherokee

Hey guys I have a 89 ltd and it won't turn over I hear the fuel pump the plugs wires and cap were changed the batt is strong I just bought it with a 650 crank it's like it wants to but won't turn over please help!!!!!

sam24th

Wait is the starter actually turning over? If the starter works but your engine wont run its probably your CPS sensor. If your starter is turning over weak check your connections at the starter, or test the starter.

1989 cherokee

My starter is cranking fast it's not slow or anything but It's like the motor won't kick in I thought it was maybe it was the fuel pump but I hear it hum when i turn the key before it would start sometimes but not others but today not at all

sam24th

Check your CPS. If your starter is cranking and you have fuel pressure, Im willing to put money on the CPS. If you have a pressure gauge throw it on the fuel rail and check the pressure. The CPS wont allow the ignition to fire if it doesnt see the correct voltage. Engine needs 3 basic things to run, spark, fuel and air. If its got fuel and air, its probably missing spark which regulated by the CPS on start up. When the sensor goes bad you can sit there and crank for an hour until your batt dies and it wont start. CPS is found on the bellhousing of your transmission. Upper driver side. Has 2 bolts going to it. Its a PIA to get to. You can drop the tranny slightly to get to it easier.

1989 cherokee

Thanx Sam so much for the help I love this forum everyone is great

DFlintstone

Guess if it's cranking/turning over but not firing/starting it's fuel or spark. If it doesn't fire with a shot of starting fluid, It's not a lack of fuel. If there is no spark, like Sam says the CPS is a common culprit. One test is to unplug it there at the rear of the manifold and probe the two wires from it for 1/2 volt, (500mv) AC while your cranking. I'm sure there are a few wright-ups somewhere for that Renix not starting. Let us know how it goes, Good luck!

cruiser54

Here's the CPS test. Just because you hear the fuel pump prime doesn't mean the hose inside the tank isn't compromised. Do the CPS test first. If you've got spark, check fuel pressure with a gauge at the rail.

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 3.5 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 it’s mounting holes with the first drill bit that just won’t fit through the original holes. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.