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Won't start - 88 4.0L mt

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Hey guys, don't know if anyone has an idea, but that's what we are here for, right? So, recently rebuilt the fuel system because she was running rough. Finished the job, and discovered a blown head gasket. Changed that last night, everything is plugged back in, and now she is not getting spark or fuel. I can hear the brand new pump kicking on, but there is zero fuel at the rail. Squirted a little ether (starting fluid) in the intake, and she still won't fire, indicating no spark either. I am going to swap out the ECU (I love working in a salvage yard) and see if that fixes the problem, but does anyone have any other ideas in case that doesn't work?

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Check it out scientifically:


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.



And see if this helps:



Renix Jeep ICU/Coil contact refreshing




The contacts between the coil and the ICU on your Renix Jeep can become corroded and loose causing a complete or intermittent no-start condition. I recommend the following procedure as a maintenance precaution to insure this is eliminated as a possible cause now and in the future.


The coil is attached to the ICU by two T20 Torx bolts. Remove these two bolts and lift the coil up off the ICU. You will see 2 pins and 2 sets of contacts. Clean both the pins and springy contact pieces with a good electronics cleaner.

Squeeze the springy contacts closer together with some needlenose pliers. Apply some dielectric grease to the contacts and bolt the coil back on to the ICU.

While you’re right there unplug the connectors from the ICU and inspect the pins in the harness connector. Make sure the pins are not retracted into the connector. Spray out the connector and the receptacle of the ICU with the same good electronics cleaner you used earlier. Apply dielectric grease to the connectors and plug them back in.


I feel this procedure should be performed at least once in the lifetime of a Renix Jeep.

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