4.0 won't run

[alfman]

1987 XJ 4.0, automatic transmission, 350,000 miles.
I have a problem where I got towed off the NY Thruway due to a fuel pump problem, the fuel pump was noisy and I couldn't hear it running anymore. Replaced pump and sender and it started and ran for approximately 5 minutes. Went to take it for a test drive and it started to cut out and died. Now no spark and no trigger on the fuel injectors. It's OBD and I only have OBD 2 scanner. Crank sensor appears OK as the fuel pump is running. I replaced the coil and module under the coil, as they were original, still no spark. I also do not have a trigger pulse in the single signal wire going into this module. Should I be looking at the distributor, pick up coil, or ECM? Any other ideas?
I am going to see if I can borrow a scanner for OBD, but haven't found one yet. Does anyone know of a cheap OBD scanner?
Thanks in advance, Al

 

[cruiser54]

Fuel pump running does not mean the CPS is running. test the CPS output.

RENIX CPS TESTING AND ADJUSTING
OCTOBER 30, 2015 SALAD 84 COMMENTS EDIT
CPS drill mod

CPS location

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 itself as shown in Figure 2 as Connector A, 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.

Another little tip to save tons of aggravation is to stick a bit of electrical tape to your 11mm socket and then shove the bolt in after it. This reduces the chances of dropping that special bolt into the bell housing. CPS bolt socket

 

[CJR]

Cruiser54,

A GREAT write-up! I did your CPS mod on my 88XJ and it worked great! I went a step further and notched the holes so that I now only need to loosen the CPS bolts to remove a defective CPS and insert a new drilled/slotted CPS. That now makes replacing the CPS a snap on the 88XJ. Likewise, I've also slotted my 00XJ different-type CPS to ease future replacements.

Thanks again Cruiser!

Best regards,

CJR

 

[cruiser54]

And Alfman, your Jeep is not OBD at all,

The only scanner you can find id the MT2500 or the REM. A link to the REM: http://nickintimedesign.wordpress.com/