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Help..no spark after motor change


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89 4.0 comanche. installed new motor, new o2 sensor, new cps sensor. went over everything 3 times and still have no spark.

Also, when key is in on position, one of the relays up by the battery is clicking really loud (the middle relay). Any help???? Any idea?????

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If you swapped also, you could have busted the crank sensor where it goes into the bellhousing while installing the motor. Pull the sensor out and see if its broken....and replace it while its out anyways if it isnt broken. If I remember correctly, the new ones come with a peice if cardboard on the end of them to set proper air gap to the flywheel, when the engine turns over, the cardboard is ground off by the flywheel and proper air gap is established. Good luck!

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I put the new sensor in after it was bolted up it was in a bag from mopar no cardboard that I could see on it. I did it this way as not to damage it. I am pretty new to vehicles with this sensor crap so my knowledge is limited except for what I have read on here. So should I realy pull this cps and try the old one?

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You could check the ohm's reading from the connector in the engine bay first, to see if the CPS is within range.

 

Here's the link to all the Renix sensors -

 

http://www.lunghd.com/Tech_Articles/Eng ... ostics.htm

 

Most common sensor that will "kill" the spark is the CPS. 2X's on checking for pinched wires.

 

Check the grounds, battery to block, block to firewall, one loose, or corroded can cause all kinds of problems. Also, check the ground at the ECU.

 

The relays on the shock tower (front to rear) Fuel pump, Ox2 sensor heat relay, B+latch relay (AC clutch - 4th if you have) If your 2nd relay is "clicking" check to see if the Ox2 sensor is hooked up, or check for a bad relay.

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Thanks for all the help guys I wish it was a new painted block its a new to me motor. The relay continues to click as long as the keys on also clicks while its cranking. Its the middle so that`s the o2 I did get the o2 off ebay no signs of it being installed before and it was a borg warner. We tried to do a good job on the grounds but will redue and recheck them and clean better today. We tied all the wires up and were realy easy in setting it in but will check the wires again also.

New thought would the distributor being in wrong or faulty cause this also? I need to put my old distributor in and reset the timing? Thats one of the few parts I used off the doner. Will do the tests on the cps also would some crud getting on the CPS just another thought I had.

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CPS needs to be kinda clean as it needs a +/- 5volts to send to the ECU before the ECU will allow the injectors and spark to turn on. It also must see a starter RPM of 300 to allow those things turned on.

As many have mentioned a pinched wire is very common and will stop that very faint signal(+/-5V) to get to the computer. So it would be a great way to get more familar with your Jeep to physically explore that all the way into the harness.

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There is NO timing to set, that's done with the ECU. The Distributer needs to be set, at #1 post, and #1 cyl at TDC on the compression stroke.

 

Even if you had the dizzy off, you should still get spark, just not running, or running rough, and possibility backfiring.

 

Check the coil pack to see if your even getting voltage out.

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Hope some one is still watching this. Even thought we changed the cps neither one the old or new is putting anything out while cranking??????????????? Any ideas? Did the flywheel have to go on in any certain relation? Also this is the one off the running motor.

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Hope some one is still watching this. Even thought we changed the cps neither one the old or new is putting anything out while cranking??????????????? Any ideas? Did the flywheel have to go on in any certain relation? Also this is the one off the running motor.

 

Oh, oh.

 

The truck is an '89, correct? That's a Renix. What year is the "new" engine? If it's a 1991 or newer, and you kept the "new" flywheel on the "new" engine -- there's your problem. The newer Chrysler injection/ignition system uses a different type of CPS than the older Renix system. The newer flywheel won't work in the old vehicle. Neither will a CPS for a '91 or newer Jeep.

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Bearings were gone sound like little gremlins in the lower end with hammers. I used the pan from my old motor had less rust. There was bronze caked in the bottom around the drain at least 1/4 inch thick. Truck ran excellent until I pulled the motor never had a problem (other than the knocking) I will have owned it for a year in October. Should also metion I used my intake, fuel rail, etc, new manafold also.

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Yea, when I read your update on the flywheel, I thought the same as Eagle, But, I think you put that to rest, using your old flywheel.

 

here's the test for the stator -

 

http://www.lunghd.com/Tech_Articles/Eng ... Stator.htm

 

I'm still thinking your not putting any voltage out of the coil, and that should be tested.

 

OK, you write the old engine ran, the replacement engine ran (I wouldn't call a replacement engine "new") So, in the words of the famous JTDesigns.........K.I.S.S.

 

There has to be something simple that got over looked, didn't get hooked up, I know, you checked everything 3 times.

 

OK......I'm going to toss out something really off the wall here........Take the ECU out, yea, I know it's a pain, open it up, and check the circuit board, look for any "burnt" resistors or any odd looking solder trails, in other words, take a close look at the board, it's a remote possibility that you might have damaged the circuit board buy shorting out the positive lead :dunno:

 

To answer your other question.........Yes, there are several of us following your topic, but, we're not all on here 24/7, we have day jobs to support our "hobby" and also spent time :wrench:

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Yea, when I read your update on the flywheel, I thought the same as Eagle, But, I think you put that to rest, using your old flywheel.

 

here's the test for the stator -

 

http://www.lunghd.com/Tech_Articles/Eng ... Stator.htm

 

I'm still thinking your not putting any voltage out of the coil, and that should be tested.

 

OK, you write the old engine ran, the replacement engine ran (I wouldn't call a replacement engine "new") So, in the words of the famous JTDesigns.........K.I.S.S.

 

There has to be something simple that got over looked, didn't get hooked up, I know, you checked everything 3 times.

 

OK......I'm going to toss out something really off the wall here........Take the ECU out, yea, I know it's a pain, open it up, and check the circuit board, look for any "burnt" resistors or any odd looking solder trails, in other words, take a close look at the board, it's a remote possibility that you might have damaged the circuit board buy shorting out the positive lead :dunno:

 

To answer your other question.........Yes, there are several of us following your topic, but, we're not all on here 24/7, we have day jobs to support our "hobby" and also spent time :wrench:

Went through simular "no start" Although it was intermitant to begin with ,it quickly became as yours ,went thru all the hoops and finally found defective ECU was the culprit :agree:

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I'm having the exact same problem, just got done with the motor swap in the XJ, and no spark. Tested the CPS, and I'm getting infinite OHMs. Pretty sure I busted the CPS either during removal or install.

 

Never thought to pull the sensor/reinstall with the manifolds off. Now I get to change it the fun way. :fs1: :wall:

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  • 2 weeks later...

Great news the manche lives and breathes again. :banana: :banana: :banana: My friend took over the job I was just to busy to keep going. He is a retired Air Force Mechanic and former Chrysler tech. It was a ground wire in the harness that comes out around the middile of the firewall and runs out to the injectors there`s a place where some smaller wires branch out of it.

 

We had to pull this up and out of the way during the swap. I stuck it under the wiper arm to hold it. Well the wires were separated and making bad contact. He soldered them and resealed and wrapped them back up and it runs great. Nice and quite no knocks no ticking from the former exhaust manifold. I can't believe how much I missed this thing for the past couple of months. Thanks for all the help everyone!

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