Engine cutting off

[drase]

I was driving and the engine cut off, I shifted into neutral before I ran over the curb, it started up and then after I hit the gas the truck jerked. When I got home as soon as I pulled into driveway it cut off. It kept turning over but would not start, then finally it did. Could this be the battery or the alternator?

[Wildman]

Sounds more like the CPS is tell you it's time for a new one.

 

You could unplug it and plug the connector back in, but that will only buy you some more time.

 

If it was the alternator, the red light would have come on, or the gauge would have shown 0 volts.

 

The trick to check the alternator, with the engine running, remove the positive battery post, if the truck stays running, the alternator is OK, if it dies, the alternator is going south.

 

Could also be bad fuel, or a dirty fuel filter :hmm:

[drase]

Sounds more like the CPS is tell you it's time for a new one.

 

You could unplug it and plug the connector back in, but that will only buy you some more time.

 

If it was the alternator, the red light would have come on, or the gauge would have shown 0 volts.

 

The trick to check the alternator, with the engine running, remove the positive battery post, if the truck stays running, the alternator is OK, if it dies, the alternator is going south.

 

Could also be bad fuel, or a dirty fuel filter :hmm:

 

What is CPS?

 

I'll check the alternator tomorrow. I just changed the fuel filter 1 week ago.

[Geonovast]

Crankshaft Position Sensor.

 

It's mounted on the driver's side top of the bellhousing. It's a magnetic sensor that picks up indentations in the flywheel, telling the ECU when a piston is near TDC and ready to fire, resulting in the ECU firing the coil.

 

If the sensor is dying, or the terminal is dirty, then the ECU won't receive the signal, or receive the signal late, resulting in the truck dying/not starting. Sometimes unplugging and plugging it back in will by you some time, but chances are it's on its way out. You can check it with a multimeter. Set it to read ohms(resistance), and probe both terminals in the sensor's plug. Should be between 125 and 275 ohms.

[Wildman]

Crankshaft Position Sensor

 

I bet you just want me to type that all out.......did you :roll:

 

Here's a link, and about 3/4 down the page will give you the testing of it, and the replacement of it, and this saves me a lot of extra typing :D

 

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

 

 

Geonovast wanted to do alot of typing before I got my reply in....... :D But, he's spot on :thumbsup:

[Eagle]

What is CPS?

 

I'll check the alternator tomorrow. I just changed the fuel filter 1 week ago.

It isn't the alternator. You can drive for a long way on the battery, and if the battery gets so weak it won't power the fuel pump and injectors, it sure isn't going to crank the starter motor.

 

The symptoms you describe are classic signs of a dying CPS. Been there, done that, ruined the tee-shirt crawling under the Jeep to change the thing.

[88pioneer]

:agree: a bad alternator would result in absolutely nothing happening when you turn the key, no accessories, lights or anything definitely no cranking. At least you can check that off your list of possibilities :thumbsup:

[drase]

Should I buy a CPS from Jeep or do they sell them at auto parts stores? Any idea how much they are?

[Geonovast]

I think you can get them at a parts store. I've never personally bought one, but I've heard they go around $70.

 

Or if you feel ok with a used one, try a WTB thread on here. I'm sure someone's got an extra laying around.

 

Or a yunkyard. Your sensor will be the same as any 86-90 2.5, or 87-90 4.0.

[Wildman]

I've heard you would have better luck with an OEM from the dealer...........

 

But, I've bought a couple aftermarket ones and had good results........(I'm cheap) :roll:

 

This is from http://www.rockauto.com -

 

AIRTEX Part # 5S1799 More Info {#33004761, SU3228}

 

Part Image

$29.79

 

STANDARD MOTOR PRODUCTS Part # PC87 More Info {19" Pigtail}

Pick-up and Crankshaft Position sensor assembly.

 

Part Image

$34.79

 

I've used the Standard, and re-placed 2-3 of them with no problem.

[Lenard]

When I was stranded up in Kansas City with a bad CPS, I went to Carquest and they charged me $50. Have not had a problem since then.

[drase]

I just called AAP and they asked if I needed the CPS with altitude or without altitude, I have a 4.0 6 cyl engine, does anyone which one I would need?

[Wildman]

Yes, I've heard of that before, you would need one With Out Altitude.

 

That would be one for the Rocky's area, like Denver, "mile high city", from you tag, your in Florida, and that's like what, below sea level :hmm:

 

Similar to some parts that are spect'ed to California Emissions.

[shawn]

this thread might apply to me too. today i was gonna post that about once a month, when I'm driving the '91, it will give a sudden hiccup, like all of a sudden for one second, the is no power at all coming from the motor, then its instantly fine again and a month will go by and it will do it once more. this month it has done it twice. --------- same thing? cps ??

[Lenard]

Yes, I've heard of that before, you would need one With Out Altitude.

 

That would be one for the Rocky's area, like Denver, "mile high city", from you tag, your in Florida, and that's like what, below sea level :hmm:

 

Similar to some parts that are spect'ed to California Emissions.

Ive heard that if you get the CPS with the Altitude, that it will give

a little more pep to the engine, is that true?

[drase]

How do you get to the CPS? I got under the truck and I know where it is but I can't get my hand between the firewall and bellhousing to reach the CPS. And it looks like I have to disconnect alot of wires if I try and reach it from the engine bay.

[Geonovast]

4.0? 4wd?

 

If it's 4wd, pull the front shaft out, makes it a lot easier.

 

There isn't a lot of room. For me, going in from the top is impossible. I can get at it by dropping the front shaft. You might have to break the bolts loose from behind the trans with a bunch of extensions.

 

Another possibility, is if you think you can get the tranny crossmember bolts out without them snapping, you could drop the trans down a few inches.

[drase]

4.0, 2wd. Its also on a incline in my driveway. God, I thought this was going to be easy :headpop:

[drase]

So with a 4.0, 2WD is the only way to get to the CPS is to drop the tranny?

[Geonovast]

No, you should be able to get at it. It's just... not fun.

 

Dropping the trans would make it easier.

[drase]

No, you should be able to get at it. It's just... not fun.

 

Dropping the trans would make it easier.

 

I just don't see how. It appears the CPS is right against the cowl. Has anyone on here replaced a CPS on a 4.0 2WD without dropping the tranny? Is so, how?

[Geonovast]

I've replaced it on a 4.0 4wd without dropping the trans.

[Wildman]

I've replaced it on a 4.0 4wd without dropping the trans.

 

 

:agree:

 

And a 2wd would be even easier :D Because you don't need to take the front drive shaft off.

 

It's not the easiest thing to get your hand up there to pull the bolts, and with my fat hands and arms.......I can do it :D

 

What every you do.........Don't drop one of the bolts down in the bell housing :no:

 

You will for sure be taking the transmission off :eek:

 

I've drop the tranny down, with taking the bolts off the cross member, but that seamed like a waste, the next one, and others, I've just done with taking the front drive shaft off.

[Geonovast]

What every you do.........Don't drop one of the bolts down in the bell housing :no:

 

You will for sure be taking the transmission off :eek:

 

Not a big deal with an automatic, you can fish it right out with the inspection cover off.

 

With a 5 speed... yeah, you might get lucky, if you bend the plate out of the way.

[ajpolitz]

No, you should be able to get at it. It's just... not fun.

 

Dropping the trans would make it easier.

 

I just don't see how. It appears the CPS is right against the cowl. Has anyone on here replaced a CPS on a 4.0 2WD without dropping the tranny? Is so, how?

 

I.ve done mine twice, once just because I thought it went bad while troubleshooting another issue.

 

Off is easy:

I used a 3/8 drive with a 12" extension, + universal (wrap the universal joint with teflon tape 5-6 time to stop the flop).

It's a little tricky at first but it will work out.

 

On:

 

On the bolts, wrap a little teflon tape around the head of the bolt. This will help keep the bolt stuck in the socket and prevent it from falling out into the bell housing. Tighten it by hand first using the extension + universal. You don't want to cross thread anything.

 

Anthony