1989 Jeep Comanche - Crank but won't turn over.

[dotnetrob]

Have a new to me 1989 Jeep Comanche Pioneer, Automatic, inline 4.0, 4x4.   Bought it a month ago, drove it 600 miles home and have started the long restoration process.  But now it won't start.  Have already found some good post on step by step things to check but have a small twist that may change the order or help diagnose the problem.

 

It has always cranked a few times before turning over.  Today I needed to move it out of the garage to get to mower.  Started it up, usual couple of cranks and it started.  Put it in reverse, got it out of the garage and it died...  first time it has ever died while running on me, of course I have only had it a month.  Now it cranks but never turns over.   Not sure if they fact it died, had a long crank in the first place, and won't start help narrow down what to test first.

 

What have I done to in the past month

1. replaced battery - had the wrong size battery in it from the previous owner - so replaced with new correct size battery
2. replaced the power and ground wires with kit from jeep cables, the power wires and ground wires that were in it junk, bare wire showing and destroyed.  replaced 2 weeks ago - has started 20+ times since then.
3. installed new radio
4. fixed rear brakes - they didn't work at all  and it failed state inspection, so had to get this done.  Now inspection is done. :) 
5. changed air filter, old one was way past due.

 

[fiatslug87]

Do you hear the fuel pump prime when you turn the key before cranking?

[Bhase]

I’m in a similar situation. I am trying to start mine for the first time after swapping to a stroked 4.7, it cranks but no spark. Doing some research I checked the CPS and the ignition coil. Both of mine are good but you should start there. Hopefully someone else knows what to check next if yours are also good. 

[dotnetrob]

19 hours ago, fiatslug87 said:

Do you hear the fuel pump prime when you turn the key before cranking?

 

Fuel pump sounds like its coming on.

[fiatslug87]

Then check the CPS as stated above. Sometimes if you disconnect and reconnect the CPS it fires up.

[dotnetrob]

26 minutes ago, fiatslug87 said:

Then check the CPS as stated above. Sometimes if you disconnect and reconnect the CPS it fires up.

 

1 hour ago, Bhase said:

I’m in a similar situation. I am trying to start mine for the first time after swapping to a stroked 4.7, it cranks but no spark. Doing some research I checked the CPS and the ignition coil. Both of mine are good but you should start there. Hopefully someone else knows what to check next if yours are also good. 

 

CPS Readings

245 ohms

.3 AC volts.  

 

will check ignition coil next.

 

[fiatslug87]

According to Cruiser’s tips 0.3v is too low.

https://comancheclub.com/topic/73466-7-–-cps-testing-and-adjusting/

 

[Bhase]

Not OP but in the same boat. I am getting 215 ohms and .525 volts. Any suggestions as to what check next? Just replaced the ignition coil and module since that was out of spec 

[Eagle_SX4]

I just ran into this issue pull your distributor cap and make sure it is turning while the engine is being started. My camshaft ate my distributor gear and it was no longer spinning.

 

The likelihood that your cam ate your distributor gear is very low but it can happen as I found out.

[Bhase]

Sweet, will do! Thanks

[dotnetrob]

On 7/24/2025 at 3:50 PM, fiatslug87 said:

According to Cruiser’s tips 0.3v is too low.

https://comancheclub.com/topic/73466-7-–-cps-testing-and-adjusting/

 

New cps install, was a pain to do.  Same results, crank no start.

[dotnetrob]

On 7/27/2025 at 4:06 PM, Eagle_SX4 said:

I just ran into this issue pull your distributor cap and make sure it is turning while the engine is being started. My camshaft ate my distributor gear and it was no longer spinning.

 

The likelihood that your cam ate your distributor gear is very low but it can happen as I found out.

 

Still learning, how do i test this.  Pull the distributor cap and try to crank it ?

[Eagle_SX4]

5 minutes ago, dotnetrob said:

 

Still learning, how do i test this.  Pull the distributor cap and try to crank it ?

Remove the distributor cap and either video the distributor or have someone watch it and make sure it is spinning while trying to start the engine. Like this.

 

I am still trying to figure this issue out myself. Even with my distributor my truck still won't start. I have tried 3 different new CPS sensors but it still won't start. I think I have the issue narrowed down to a bad ground. You can follow along in my thread here.

I hope to get my truck running today.

 

[dotnetrob]

39 minutes ago, Eagle_SX4 said:

Remove the distributor cap and either video the distributor or have someone watch it and make sure it is spinning while trying to start the engine. Like this.

I am still trying to figure this issue out myself. Even with my distributor my truck still won't start. I have tried 3 different new CPS sensors but it still won't start. I think I have the issue narrowed down to a bad ground. You can follow along in my thread here.

I hope to get my truck running today.   

 

 

 

Greatly appreciate the help.  Rotor is spinning when i crank it, even saw a spark from the center on the distributor cap.

[fiatslug87]

Will it start if you put starter fluid down the TB?

[dotnetrob]

1 hour ago, fiatslug87 said:

Will it start if you put starter fluid down the TB?

 

Went and got some new start fluid, sprayed in throttle body and it turns over for a second. Guess i need to recheck pump, maybe replace fuel filter, existing one looks ancient and research which relays to check. Its progress 😁

[fiatslug87]

By turning over you mean it started and ran for a second, right? Jump the fuel pump ballast resistor on the driver side fender and try starting. You can also check fuel pressure at the rail, Cruiser’s tips has the procedure.

[llhat]

but define your terms....  just so everyone is on the same page

 

Crank but won't turn over.

 

The starter turns over the engine in the process of 'cranking'...   or attempting to start 

 

what is happening to you is it is cranking, engine spinning, but will not  run............   is that correct??

 

by the posts above you saw a spark from distributor,  correct...

 

air + compression + fuel + spark =  some reaction.. though it may not be the engine achieving RPMS... could be a backfire or after fire

 

agree on verifying fuel pressure at the test port on the rail...... 

[dotnetrob]

On 8/2/2025 at 12:55 PM, fiatslug87 said:

By turning over you mean it started and ran for a second, right? Jump the fuel pump ballast resistor on the driver side fender and try starting. You can also check fuel pressure at the rail, Cruiser’s tips has the procedure.

 

Correct, if i put spray starter fluid directly into the throttle body it starts and run for a second or two.  Without starter fluid it just cranks and engine doesn't start. 

 

Jumping the fuel pump ballast resistor didn't change the results with or without starter fluid.

 

Got a R.E.M.II+ from NickInTimeDesign today.  Plugged it in to get some readings.  Still learning all the workings of the REM but below are some screens from the diagnostic section, not sure if they help at all.  Only tried starting it without starer fluid to get readings.  Didn't try putting in starter fluid so that It would run for a few seconds, not sure if that would results in different/altered data.

 

Did see a message saying No CPS signal, not sure if I should put old cps back since it may not have help swapping it out.

 

Current next steps I plan to test/try.  Unless I should try something else first.

1. Check if fuel pump is coming on, hard for me to hear over the ignition buzzer.  Got under the jeep last time while some turn the ignition to the start position and pretty sure I head the fuel pump.  Just waiting on an extra set of hand so I can retest.
2. Check fuel pump ground by tail lights.  I did swap out the tail lights weeks ago, have driven it many times since, but will check to make sure it still good and attached, may move as per recommendation once I get it running again.
3. Checking fuel rail pressure, don't have pressure gauge I can use for this, getting one today
4. Ordered a fuel filter, may or may not change it out depending on results of other test.

[fiatslug87]

I would leave the CPS alone, since it starts and runs with starting fluid it’s getting spark. Concentrate on fuel delivery. The TPS should be at 17 at idle when you get it running.

[Eagle_SX4]

7 minutes ago, dotnetrob said:

Correct, if i put spray starter fluid directly into the throttle body it starts and run for a second or two.  Without starter fluid it just cranks and engine doesn't start. 

 

7 minutes ago, dotnetrob said:

 

Did see a message saying No CPS signal, not sure if I should put old cps back since it may not have help swapping it out.

I just ran into this a similar issue. My rem said CPS Crank fault but I had spark which didn't make any sense. You also have spark because it would not fire with starting fluid if you didn't.

 

I noticed that the CPS Crank fault doesn't come in immediately when cranking it takes a few seconds to turn on. Which leads me to believe that the computer cuts spark after it doesn't fire. And you either have a fuel issue or your distributor is not indexed properly.

 

Don't change your CPS out. It is probably not the issue.

 

Based on all your symptoms you definitely have a fuel issue and first you need to check if your fuel pump is running. It should turn on for about 2-3 seconds when the key is first turned on then the fuel pump will shut off. You will be able to hear the pump run. If you can't hear the pump run. That is where I would start.

[dotnetrob]

44 minutes ago, fiatslug87 said:

I would leave the CPS alone, since it starts and runs with starting fluid it’s getting spark. Concentrate on fuel delivery. The TPS should be at 17 at idle when you get it running.

 

42 minutes ago, Eagle_SX4 said:

 

Based on all your symptoms you definitely have a fuel issue and first you need to check if your fuel pump is running. It should turn on for about 2-3 seconds when the key is first turned on then the fuel pump will shut off. You will be able to hear the pump run. If you can't hear the pump run. That is where I would start.

 

Video of fuel Pump, sounds to me like its coming on.  Hopefully I am correct.

 

Also have video of it firing up with start fluid sprayed in it, don't think it adds much info.  

 

[fiatslug87]

That’s a weird gurgling sound. You can pull the fuel line from the filter, put it in a jar and try starting, see if the pump is delivering anything. Or just pull the pump to see if everything is connected and bench test it.

[Ωhm]

Using a voltmeter or 12vdc testlight (preferred) check for Battery_Voltage on the following pins (use battery_negative terminal for ground):
D1_5:  Battery_Voltage (Hot at all times)
D1_6:  At KEY ON, (Hot for 2-3 seconds). During CRANK, (Hot at all times).
D2_4:  At KEY ON, (Hot at all times). During CRANK, (Hot at all times).

[Eagle_SX4]

1 hour ago, dotnetrob said:

Video of fuel Pump, sounds to me like its coming on.  Hopefully I am correct.

Your fuel pump is coming on but is sounds like the pressure line has come off of the pump and it is just moving the gas around in the tank. I would pull you pump out and double check that everything is hooked up as it should be.