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CPS replacement, please help...

caseydunham

NAXJA Forum User
Location
hazlet nj
Hi,
I'm new to this board, and even to trying to fix stuff on my own.
The story sounds like everyone elses, stalling once in a while then more often, and then, dead.
I usually was able to get it started after a stall, but the one time, just deas, lights and everything this time, guy pu a new battery in it, he said he load tested it and it was at 0. He also said the cable from the dist cap to the ignition coil was a little lose and after he tightend it, it was ok.
After not even a week, same deal, started stalling, progressively worse, and now, dead.
It is giving me code 11, which is the CPS, and I have already read about doing it.
My questions, should I check the icnition coil first? And if it isn't the coil, and is the CPS, is it better to get from the dealer ($116), or AutoZone ($57, Wells)?

PLEASE HELP, I can't take this anymore...
 
ignition failure is a rare thing with a 4.0
CPS failure is much more common.

The board needs some more information though.
Pertinent things to post anytime you're asking a technical question:
Model Year
Motor
Transmission

welcome to naxja
 
Since you've got a 1994, your control system is OBD-I.

Code 11 in OBD-I means "No Ignition/Crank Reference Signal," or "No ignition (CPS) reference signal detected during engine cranking" (from my site - http://www.geocities.com/JeepI6Power/obd1.html - and originally compiled from FSMs.)

Sounds to me like your CPS is going - considering the environment it operates in, no surprise here. The CPS is located (looking forward) at 11:00 on the bellhousing at the rear of the engine. If you lift your hood and stand on the driver's side near the firewall, then look down alongside the cylinder head, you should see it.

However, it's easier to get to from the bottom.

You'll want two and a half to three feet of extensions for your socket wrench, and either an 11m/m (or 7/16") socket and a universal joint, or an 11m/m (or 7/16") socket with the universal joint inbuilt. I find the latter easier to deal with.

Before you remove the screws, be sure to pack the socket with grease. Replacing an OEM CPS should take less than an hour (I've got practise - and I've got it down to about 10 minutes...) but if you drop one of those screws into the bellhousing, it rapidly becomes an all-day job, since you'll have to pull the transmission to retrieve the screw. Also, it's an odd "shoulder screw," so replacements are (for now) OEMR only (I'm working on that as well.)

Anyhow, the grease will help to hold the screw - it's also advisable when you're starting to put the screws back in.

It's not a difficult job - technically speaking - but it is a bit exacting, and does demand care. You should not have to do anything for "computer relearn" once you replace the sensor.

You may want to check my website for your reference - I've actually got a 1994 FSM, so you've got 1994 technical data (including OBD-I codes!) to draw on. Link in sig.

Since you're learning mechanics, you're going to learn a whole new language - so here's some help to get your started understanding all these words we throw around...

FSM - Factory Service Manual. Miles better than manuals put out by Chilton's or Haynes.
OEMR - Original Equipment Manufacturer Replacement. Used when a part can't be found in the aftermarket - it's said to be "OEMR only."
OBD - OnBoard Diagnostics. Suffixed with either "I" or "II" - OnBoard Diagnostics Generation One (to 1995) or Generation II (1996-present.)
 
Nothing wrong with aftermarket - if you stick to good brands.

If you can find Borg/Warner, ACDelco, or Bosch parts locally, you're doing well (getting a good part AND saving some money!)

Wherever possible, you should buy "quality" aftermarket parts - and, if you're still running now, you can even mail-order Crown or even OEM - for less than what you'd spend locally.

Although, if you do mail-order the part, I'd say buy two. That will give you a spare for the next time it goes out (although the rated service life is >150Kmiles, no point in waiting. It's a small spare.)
 
Thanx to everyone for their input...got it out in 10 minutes...
Can't get the part until tomorrow, so I would like to test this...
I don't know how?
Any advice???
 
From 1994 FSM...

"CRANKSHAFT POSITION SENSOR TEST

"To perform a complete test of this sensor and its circuitry, refer to the DRB Scan Tool." (Which you probably don't have. Keep reading... -Ed.) "Also refer to the appropriate Powertrain Diagnostics Procedures manual. To test the sensor only, refer to the folowing:
"The sensor is located on the transmission bellhousing at the left/rear side of the engine block."

"1) Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
"2) Place an ohmmeter across terminals B and C." (Looking into the terminal, with the locking tab UP, "B" is in the middle and "C" is on your right. -Ed.) "Ohmmeter should be set to 1K-to-10K scale for this test. The meter reading should be open." (Infinite resistance, or open circuit. -Ed.) "Replace sensor if a low resistance is indicated."

Since you've got the thing out already, you should be able to access it much easier - but recall that you don't need to dismount the sensor if you suspect trouble - just disconnect the wiring and get out your meter.
 
Re: CPS replacement, please help...update

Ok, I just got back from the Jeep dealership. I got the new CPS, and tried to test it. It reads the same thing! What else could it be? The code was 11...
 
Re: CPS replacement, please help...UPDATE!!!

Ok,
Got thie CPS in, truck started right away...
Only thing, it is running very rough. Almost "puttering" if you will. It ran great before this happened, any idea what it could be?
 
I'm guessing while you were originally attempting to start you were cranking it over and over. With that said it's possible you have fouled your plugs.

If it were mine that would be my next move. Might as well swap the cap and rotor too if you can swing it pal.

Come to think of it, did you mess with the plug wires at all when you were diagnosing the problem? Could a plug wire be loose or switched position putting the firing order out?
 
John B said:
I'm guessing while you were originally attempting to start you were cranking it over and over. With that said it's possible you have fouled your plugs.

Well if the crank position sensor was bad, it should have been firing the injectors either.
 
lawsoncl said:
Well if the crank position sensor was bad, it should have been firing the injectors either.

Would not have fired the injectors? I wasnt aware of that...thanks for setting me straight.
 
Did you disconnect the battery when you pulled the sensor?
I'm under the impression it's best to remove the negitive terminal when doing anything electric. After about a half hour the computer will reset itself and make and create a new fuel curve and what not. If you didn't disconnect the batt when doing the work, maybe the computer is still trying to run the engine off the information of the bad sensor information.
Also, I totally agree with one of the previous posters, make sure you didn't knock a spark plug cable loose while poking around the engine, I did that once and spent a week trying to figure out what was wrong.
Good luck
 
Update...
Ok, I guess this was just an oversight. I went outside this AM, and the tailpipe was hanging very loose...
I looked underneath, and the mount that was holding it on snaped...

My question is this...
would that being loose cause it to drive rough?

Any help appreciated...
 
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