No start dilemma

[Eagle]

My '88 MJ 4.0L is dead. I need ideas.

 

I went to use it a couple of weeks ago, right after a couple of days of heavy rain. Fuel pump runs, engine cranks, but go start. Once the rain had stopped, I did the unplug & replug on the CPS connection and it fired right up. "Great," I thought. Needs a CPS.

 

I wasted several HOURS on Saturday installing the new CPS. (It's a 5-speed, and there's no way to get humanoid hands up past the clutch hydraulics. I have no skin left on my right wrist.) It's in, and I didn't even drop the upper bolt into the bell housing. That's the good news.

 

The bad news is that it still doesn't start. My brain is fried. I can't check the new CPS by the method in the FSM, because they want me to test the ohms with the engine at operating temperature. How the blazes can I get it warmed up if it won't start?

 

Any other ideas?

[JeepcoMJ]

wait?! EAGLE IS ASKING A QUESTION?

:P

 

j/k.

 

 

well, it's not the CPS then is it?

[86FUBAR]

Had the same problem with my bros s10 , wouldnt start after a heavy rain i spent weeks testing every little sensor , chasing wires and also tried to hook up the snapon scanner i got from work and the truck didnt want to talk to me, finaly came to the conclusion that the ECM got wet and fried . so i replaced it and it works now .

I'm not saying that ur ecm is bad but somethn worth looking into if nothing obvious pops up

[Oizarod115]

couldn't be the CPS wiring could it? or it wouldn't be the first bad CPS (hasn't someone had trouble with that before?)

[Geonovast]

If your computer is dead and/or dying, I have one from an 88 4.0 5 speed 4x4 XJ that works good.

[Eagle]

wait?! EAGLE IS ASKING A QUESTION?

:P

 

j/k.

 

 

well, it's not the CPS then is it?

What can I tell you? I'm an analog dinosaur living in a digital world. I grew up racing cars with artifacts called by strange-sounding names like "carburetor" and "points" and "condenser." This new-fangled electronic stuff baffles me. If I lived in a state with no emissions testing, I'd dump all that stuff and revert to an old AMC 258 ignition with a Weber carburetor in a heartbeat.

[Twisty]

So with the new CPS you must not be getting a spark. Do you need to test the truck wiring harness at operating temp, or the CPS at operating temp? If you need to do the CPS, why not stick it in an oven at ~150 degrees? Maybe you could try it with the old one to see if it was the problem. If it checks out ok, then its another problem.

[DirtyComanche]

It doesn't matter what the CPS does at temperature if it doesn't work cold.

 

 

Pull the plug, put the ol' analog ohm meter on it and see how bad it is. All mine did the infinitive ohm thing when failed. If it's within the hot spec when cold, it SHOULD work. Then put it on the Mv setting and bump the starter over by jumping the ignition relay. See if it makes a signal.

 

 

Failing that, maybe look at a few other things... How wet is wet?

[Pete M]

There was a time when a hard rain would find it's way in the engine compartment and through the firewall to drip down the back of my fuse box in the 88. It was essentially my fault it got inside the cab because I removed the factory firewall grommet to run some new wires, but the rain was finding it's way past the weather stripping at the back edge of the hood. How does this relate to Eagle? I'm not entirely certain. I didn't get much sleep last night. Thank goodness for Firefox spellcheck. :D

[mjeff87]

[i'm an analog dinosaur living in a digital world. I grew up racing cars with artifacts called by strange-sounding names like "carburetor" and "points" and "condenser."

 

You still have an old fashioned timing light stashed somewhere? (I did, but gave it to my neighbor :D )

 

Hook it up and see if you are getting spark, and troubleshoot from there. If'n ya got spark, pull a plug and see what they look like. My neighbor wheeled his brandy-spankin new 7 HP Honda mower over to me last night because it "just died" on him. He was giving it to me and going to get a new one. Five minutes later and a freshly filed spark plug, and I gave him his mower back :roll:

 

CPS's differ from auto to manual, although I don't know exactly what the difference is.....maybe you picked up the wrong one and the tip is too far from the trigger wheel, or flywheel (?)

 

Jeff

[ORCA]

Did you hit the ole starter with ye olde hammer yet? I know it's a little rudimentary but it's usually my issue with rain + no starts.

 

I'm an analog dinosaur living in a digital world. I grew up racing cars with artifacts called by strange-sounding names like "carburetor" and "points" and "condenser."

 

BTW wtf are "points" and "condensers"? ;) :bowdown:

 

hahaha :headpop:

[Wildman]

Eagle - I re-read this post several times, I think you answer your own question-

 

, I did the unplug & replug on the CPS connection and it fired right up

 

I assume that was the old CPS, yes?? and then you installed a new CPS. And assuming that you got the right year, i would really look into the connector, and/or the wiring.

 

And was there not a Service Bulletin regarding wiring the CPS directly to the ECM years ago??

 

I understand the FSM say to test the CPS with the engine at operating temp, to throw the ECM into "closed loop" but that's not posible :nuts:

 

I've tested the CPS before, cool, and got the reading that were with in range on the book, I would still test the new one this way.

 

I had to change a CPS on one MJ, and belive me, it's worth droping the trans support, and droping the trans down enought to reach the CPS, and I'm sure my hands are alot larger than your's :D

 

And I know what "points" and "condenser" are, and have the gray hair to prove it :brows: I'm sure glad to work on electronic ignition any day!!

[Eagle]

Yeah, there was a TSB on replacing the wire harness between the CPS and the ECU with a pair of direct wires, and it happens that I bought the CPS that comes with that replacement harness. I'm thinking that I just may have to dredge up a copy of that TSB and do the upgrade.

 

The other thing I'm wondering about is that this truck still has the C101 connector on the firewall. I hay try unplugging that a couple of times to see if there might be a bad contact inside that can of worms.

[FxRacing282]

have you checked the distributer and the cap?

[Wildman]

The TSB is posted in here -

 

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

 

Under the CPS article.

 

After looking at that, you might want to go back to "points and condenser" :eek:

 

And FxRacing282, brings up a good point about the distributer, and check the

CAM Position Sensor located in the "distributor" Also.

[Eagle]

Small world department: Eric Giordano (a.k.a. JabbaThaHut) used to work at my dealership and we used to wheel together. Then he left the dealership and dropped off the face of the earth. None of the guys at the shop or in his old club have any idea what happened to him.