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Whats the signs of a bad CPS????

G

gptherezonlyone

NAXJA Forum User
Location
Wilmington, NC
Help, I'm about to sell this thing and buy something foreign.
 
When mine died, it went from operating perfectly, to dead on the side of the road in maybe 3/4 mile. It stumbled & stalled maybe 3 times, then would crank fine but not fire. (sorta feels like it ran out of fuel)

HTH and don't throw the old sensor out right away. If a new one doesn't fix your no-start, then ya got a spare :)

On my older Jeep it's a pair of 11mm bolts and the sensor is on the bellhousing at approx the 11:00 position.
 
Basically what Woody said. I replaced my CPS six months ago. Initially my engine would drop the rpm or stall altogether on the highway and restart after a few seconds. At the time I thought it might be the fuel pump but that checked out OK. There were no codes from the PCM either so no pointers to the actual problem at the time. Then it began to stall more frequently and take longer to crank. Eventually it got so bad that the engine wouldn't stay running for more than a mile so I got it replaced. I've had no problems since then and the Jeep is back to its old reliable self (knock on wood).
Just replace the sensor and you'll be happy again. Maybe you'll change your mind about selling the Jeep. I'd never sell mine.
 
crank shaft positon sensor

my xj would idle and run great up to 15 miles per hour then start to stumble and shake and then die. new sensor fixed problem.
 
The next time the Jeep starts acting up, trace the CPS to the connection. Since the connectors are self cleaning unplug and replug the connection a few times. Then try starting the Jeep. More then likely it will start up. If this happens its time to replace the CPS.
 
question re this. my CPS is going bad and the previous owner just cut out the plug and spliced the wires, can I splice in a new plug or can I just resplice the wires???
 
Does anyone know about the paper between the CPS and the flywheel. I have never saw this on my 93' but I sure do eat thru CPS's. I'm only asking because the FSM calls for it. If it should have paper could you use a piece of masking tape?

Also every CPS that I had that has gone bad, Autozone (Wells Brand) and the original OEM one, they have been magnetized. Magnetized enough to stick to the firewall.

As far as symptoms, doesn't start, idles rough then dies. Sometimes I get the code "11" sometimes I don't. This weekend I got a code "54" camshaft position sensor, in the distibutor. I swapped out the distributor, it started but still had a rough idle. I swapped in an old CPS, so far so good. All computer codes are clear now.
 
first, second, third, fourth, fifth time CPS goes bad and on just unplug the connection (right behind the Valve cover) and then plug back in. When that stops working then replace it. I've been doing that for 20,000 miles now (about 10 times) and it won't die.



Buying something foreign is a good idea. That way when something goes wrong you KNOW you can't fix it. Alleviates all guilt of being dumb/lazy. That said (laziness) if a search had been done there would have been a wealth of information that popped up. In the OEM forum.
 
Paper? What paper?

If you are 91+, go to Quadratec and order a few. If you're 90 or older, it's OEMR only. I have three XJ's - 87, 88, 89, and no-one makes aftermarket CPS for them (damn.)

The plug is, IIRC, a regular Delco 3-pole Weatherpack with only two towers used, so why cut/splice? If it's something silly, replace it with the Weatherpack (available from a local with the Motormite "Conduct-Tite" line) and save the headaches for next time.) Typical service life of the OEM unit is about 150Kmiles, but I did just replace an original on my 88 at 220K!

Make sure the connexions are clean - I go so far as to blast mine clean with solvent and apply a bit of Ox-Gard anytime I have to take it apart. Works wonders...

The CPS is pretty much an "all or nothing" deal. Since it generates the timing signals for fuel and spark, you can pretty much assume that a "crank-no start" fault will be the CPS. Check and replace as required. They can be tested with a meter - perhaps someone here can get to their FSM easier than I can?

5-90
 
Markm80521 said:
first, second, third, fourth, fifth time CPS goes bad and on just unplug the connection (right behind the Valve cover) and then plug back in. When that stops working then replace it. I've been doing that for 20,000 miles now (about 10 times) and it won't die.
Click to expand...

Do carry a spare and be ready to replace it on the side of the road though if it does decide to die completely :D
 
Kejtar said:
Do carry a spare and be ready to replace it on the side of the road though if it does decide to die completely :D
Click to expand...

Remi,

Wouldn't it be better just to replace it at home where it is safe instead of the side of a busy highway someplace!

hinkley
 
ok.... if you didn't get the slight hint I was trying to relay I will come out and spell it out: if your CPS seems to be needed to be disconnected and reconnected as it's getting stuck or hung and cleaning the connection doesn't solve it, replace it with a new one and keep the old one as a spare. Based on the location I don't know who would want to replace it on a hot engine anyways.....
 
If you are 91+, go to Quadratec and order a few. If you're 90 or older, it's OEMR only. I have three XJ's - 87, 88, 89, and no-one makes aftermarket CPS for them (damn.)
Click to expand...
CPS for 89 cherokee , the '91 and up uses Wells SU 369 ($49.99)and carries the same warranty.

5-90, I thought the same thing cause I couldn't find it on the web site, but when I did a search instead of paging through their lists, it came right up. :wave:
 
Kejtar said:
ok.... if you didn't get the slight hint I was trying to relay I will come out and spell it out: Based on the location I don't know who would want to replace it on a hot engine anyways.....
Click to expand...

Well that is what you were telling him to do.
 
Pssst..... Got an extra one. Know how to change it. Doesn't make since to change it since the handful of times that it seems to have died, you unplug it and plug it back in and the car cranks up like a champ and runs perfect for another 3-6 months.

Of course now that we've talked about it, it will fail completly next time I'm on the highway and I will blame YOU! All of YOU! NAYSAYERS!:flipoff:
 
Markm80521 said:
Pssst..... Got an extra one. Know how to change it. Doesn't make since to change it since the handful of times that it seems to have died, you unplug it and plug it back in and the car cranks up like a champ and runs perfect for another 3-6 months.

Of course now that we've talked about it, it will fail completly next time I'm on the highway and I will blame YOU! All of YOU! NAYSAYERS!:flipoff:
Click to expand...
So are you stating that the Computer is at fault. When you unplug the CPS, the computer then resets or learns the new signal. I'll have to do some more touble shooting, maybe find a good oscilliscope to see the acual signal. HMMM something to think about.
 
ChuckD said:
So are you stating that the Computer is at fault. When you unplug the CPS, the computer then resets or learns the new signal. I'll have to do some more touble shooting, maybe find a good oscilliscope to see the acual signal. HMMM something to think about.
Click to expand...

Well.. to throw the wrench in here it might not necessarily be the computer at fault. When my CPS was acting up, all I had to do was sit for about 10 ~ 15 minutes and then it would startup again on the first crank. So the amount of time that it takes to go out, pop the hood, unplug it might be the result of the same....

On the other hand, it is possible that there is a timing loop inside the comp that gets hung and deadlocks waiting for input or output and the wait just gets past a timeout that resets it and it is the same as the unplugging and plugging in of the CPS. Now to even complicate things, what if it is the CPS that causes the lockup and then when unplugged it resets both the CPS and the computer? :D One of these days I might be tempted to look at the logic used in the computer, although I have a feeling it will result in a major headeache.
 
Kejtar said:
Well.. to throw the wrench in here it might not necessarily be the computer at fault. When my CPS was acting up, all I had to do was sit for about 10 ~ 15 minutes and then it would startup again on the first crank. So the amount of time that it takes to go out, pop the hood, unplug it might be the result of the same....

On the other hand, it is possible that there is a timing loop inside the comp that gets hung and deadlocks waiting for input or output and the wait just gets past a timeout that resets it and it is the same as the unplugging and plugging in of the CPS. Now to even complicate things, what if it is the CPS that causes the lockup and then when unplugged it resets both the CPS and the computer? :D One of these days I might be tempted to look at the logic used in the computer, although I have a feeling it will result in a major headeache.
Click to expand...
Mine acts the same way, but I do know at times that I replaced my CPS. I was magnetized and I know it is really just a simple pickup coil. When they get magnetized obviously the copumter must be getting a false signal.

Now what about the Paper, the FSM calls for it. This may help with the magnetizism problem. I do know I need to take care of this, otherwise I need to buy a CPS sensor company. :D
 
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