My 89 quit and won't start now

[vfb]

Hi folks,

Having a problem with my 89 4 litre. It's been working fine and just now while plowing snow it quit. And won't start again.  Plenty of battery and I did get it to fire a short time by using some starting spray,  but it wouldn't keep running.   Now it won't fire at all even with that,  or a bit of gas poured in the intake.  

I jumped the ballast resistor even though I didn't  think that was it, because it understand if that's the issue, it'll start and quit right away.    I can hear the fuel pump running for a second or two like usual when I go to start it but it just turns over and won't fire.  It's in an awkward snow bank right now so not easy to get to anything.

I'm not a mechanic so the next step is a tow truck unless I can find something easy and obvious.  Any suggestions? thanks

[MiNi Beast]

let it cool a bit. check wiggle cps wire connection, check distributor ensure spark and dry. are you on a angle? 

[89 MJ]

Are you getting spark?

[vfb]

Thanks!  Not too much of an angle  luckily...... but will go now and start wiggling and checking distributor. 

 

I'll check for spark but I assume so because it did fire with starting spray

[vfb]

I let it cool and wiggled connectors but no luck. Now no start even with the spray.   Also double checked that I have fuel.  Is there a way I can check for spark if I'm on my own?

[MiNi Beast]

pull boot off and a plug or if have extra one put in boot lay it engine where you can see it from inside and crank or jump the starter with a screwdriver while holding the plug against block. 

[vfb]

Thanks ... that's a good idea. I will do that tomorrow.   I'm beginning to think about the coil too because just as I was quitting for the day, I tried it again and .... it started!  I ran it for about 5 min and it revved fine and I even backed up a foot or two. Then I shut it off, and no start again.  Maybe I didn't let it cool off long enough before.  I had this once on another truck where it wouldn't start unless the coil was totally cold.  Not sure if that would cause it to quit while running though. 

 

[JustEmptyEveryPocket]

Time to check your CPS function. 

 

Read THIS PAGE and follow the test exactly as described. Report back with the number. It should be >=0.5 reading on the volts AC scale. 

 

A failing CPS can shut down your truck and cause a crank, but no start situation. Then when everything cools down completely it will run again for a while.

[MiNi Beast]

[vfb]

Today project: finally learn to use that multimeter.

I'm really hoping it's not that I need a new CPS.  That's beyond my capabilities I'm afraid

[MiNi Beast]

simple deal two bolts. you can do it. just need a few extentions. 

[vfb]

Thanks for the encouragement ....  I'll try the testing first.

 

Winter, no indoor work space, and being an old geezer make it a daunting prospect though.

 

 

[JustEmptyEveryPocket]

Test first, lets make sure the CPS is an actual problem. Then worry about how to fix it.

 

Like MiniBeast said, its fairly straightforward, just time consuming.

[MiNi Beast]

i have it down to about a 15 mins swap. only done it 20+ times. 

[vfb]

Well, you guys don't realize what a novice you're dealing with.  So before anything I tried again this morning and it started fine and was pretty consistent in restarting, except for once.  Cleaned the CPS connectors and I tried to get a reading, but think I must have something set wrong. Is this the correct way to hook it up? Mostly nothing happened except once it jumped from zero to read .4 but then flashed back to 0.00.

Appreciate you guys bearing with me. 

 

[MiNi Beast]

novice ha. been there and in fact never even used what you have there. so I'm no help on working that tool. but i say pick up a cps and swap it out as as a newb myself that what someone told me to do so i learned about the factory external torxs 10m bolts that bolted on the crank positioning sensor  to the 11 o clock position on the back side of the engine where you could use 28.5" extension on a rachet and slowly turning counterclockwise to get the bolt to pop with release and you swap these bolts out a standard bolt head type and install a $30-$50 Cps that are known to be common failures amongst the 87-96 era xjs and mjs, so the idea being as a newb you are just hoping and swapping parts that it might fix your jeep, being a costly expense if it in turn doesn't fix said problem. now however in my 14years experience learned i did not waste money buying a cps as i have a few times swap out the cps as i have been stranded like you in the middle of the trails of nowhere . so a safe bet as good spare. however with electrical gremlins still found in our MJs it is best to learn how to use the muti-meter tool for it is only to our advantage. i will do so with you now. i wanna say it has the volts be.5 seems legit.    

[87MJTIM]

You want to be measuring DCV on the 20 scale.  Car electronics run on DC not AC.

[vfb]

 

Ya, I got it on sale after hearing so much about those electrical gremlins.  This is the first time I've needed it and definitely wish that I'd tried to learn it during the summer when it was more pleasant weather!  And you're right about getting a new CPS. I'll see if i can find one next time I go into town.   Even if this issue turns out to be something else, good to have it around and when it warms up I can learn to install it.

[vfb]

5 minutes ago, 87MJTIM said:

You want to be measuring DCV on the 20 scale.  Car electronics run on DC not AC.

 

Ok thanks. I'll try that tomorrow.

I guess I'm still having trouble understanding the terms. I did think cars run on DC, but was going by this on Cruisers site:

 

Quote

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.

 

DUH! What am I missing?

[MiNi Beast]

you plug it into your house. 

[JustEmptyEveryPocket]

3 hours ago, vfb said:

DUH! What am I missing?

For most things on vehicles Tim is right, you measure in VDC or volts direct current. However, the CPS produces an AC wave form because of the 'pulses' from the tooth pattern on the flywheel as it goes around.

 

Make sure your test leads are on the wires going to the CPS itself and crank the engine. You should be getting some reading. If you see nothing, then I would assume your leads aren't staying on the pins in the connector. Sometimes I use paperclips to backprobe a connector I want to measure. That makes it easier to get a solid reading. Can you get someone to help you? Often I can bribe my wife to come hold test leads and read the DVOM for me, but YMMV.

[cruiser54]

12 hours ago, 87MJTIM said:

You want to be measuring DCV on the 20 scale.  Car electronics run on DC not AC.

Renix CPSs generate an AC signal.

CRUISER'S MOSTLY RENIX TIPS

RENIX CPS TESTING AND ADJUSTING

OCTOBER 30, 2015 SALAD 113 COMMENTS

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. 

[vfb]

Ok, as long as my multimeter is set properly, I'll work on getting a better connection with the pins. I feel sure it's the right connector.  I assume you pin the paper clip right onto the connector pin? I'll try that today.   Tomorrow I may have someone to help.

[vfb]

14 hours ago, JustEmptyEveryPocket said:

You should be getting some reading. If you see nothing, then I would assume your leads aren't staying on the pins in the connector. Sometimes I use paperclips to backprobe a connector I want to measure. That makes it easier to get a solid reading.

I think that was it. I used alligator clips and got a reading. It started at .4 then fluctuated between .6 and .8  Is this ok or too much?  I know .5 is ideal. 

Should I check the coil next?

[MiNi Beast]

i would have checked coil first.  yeah verify spark. cps controls when it sparks as well when the fuel is injected. however I'm thinking you should have spark as it has started for you just hit and miss. perhaps a weak spark or carbon build up under cap, so check there as well. need good spark at the right time to keep running eh.