1998 jeep cherokee crankshaft position sensor symptoms

91 (HO) XJ AW4

Quick question: if my Crank sensor is bad, but my cam sensor is ok will I still get injector operation? Or is it no cps=no spark no fuel

am trying to avoid pulling the distributor to replace the pickup

If you have a bad crank sensor, your vehicle will cut out completely just like it died......if it is just going bad, it may do this intermittently and start back up on its own.

my issue is 7/10 times i get weak or no spark resulting in a no start condition. my plugs are not getting wet during the no start, so i'm not getting fuel. will start and run with starting fluid although it still starts hard even with that.

edit: on other occasions, it will start on its own. dies if you give it more than 3/4 throttle. runs strong otherwise.

The only way to tell is to test the sensors themselves, use a manual to find out the specs for your specific application. I have only had one Crank sensor go bad and what it did was just cut the engine out completely liek ti died but all my guages showed normal and the engine cutting out only lasted a few seconds. The problem got worse over time and it cut the fuel and spark to my engine. Did you check your coil as this could be the route cause for weak spark too.....a coil may act good and under certain circumstances act up such as getting colder or warmer temps or even moisture in the air such as rain or high humidity.

Also forgot to mention that 02 sensors can have the same symptoms, this is why you should test the sensors unless you do not mind just replacing random sensors until you find the one that stops the problem......this can get very expensive

Appreciate the help. I do intend to test the CPS before I change it, sync/cam sensor too if I can find the instructions (My hanyes doesn't even mention testing.) Will probably wind up replacing the coil too. I'm taking this out of state in the later part of this summer and would rather drive away knowing the typical failures are already taken care.

haynes anual

Appreciate the help. I do intend to test the CPS before I change it, sync/cam sensor too if I can find the instructions (My hanyes doesn't even mention testing.) Will probably wind up replacing the coil too. I'm taking this out of state in the later part of this summer and would rather drive away knowing the typical failures are already taken care.

Just a suggestion......throw the haynes manual out and get a Chilton's manual.....the Chilton's manual does tell you how to check those sensors......I am looking at it as I am typing this to you lol.

You won't get any fuel if the crank sensor is bad; the PCM relies on the crank sensor signal to know when to open the injectors. The fuel pump will only run for a second after you turn on the key with no CPS signal because the computer sends a "kill" signal to the automatic shutdown relay if no CPS signal is present (the computer thinks the engine has stalled and cuts fuel for safety reasons). If you do have a CPS signal the fuel pump should run while cranking.

Don't go entirely by testing the CPS with an ohmmeter, as this can lead you astray. My CPS tested fine but was indeed bad. If you've got no fuel AND no spark this is the place to start looking.

There is a quick and dirty way to test your CPS circuit. First have somebody crank it while you listen at the tank for the fuel pump. If it runs while cranking your CPS is OK. If it only runs for a second and then stops your CPS is not putting out a signal. If this is the case you can double-verify it by disconnecting your CPS at the electrical connector at the back of the intake. Plug a known good CPS into the harness, turn the key on, then move the magnetic end of it back and forth very close to a steel or iron engine part (gotta be something magnetic, not aluminum - I used a metal bracket on the engine). You should hear some relays click and the fuel pump will run. If this happens you can go ahead and replace your CPS. If it still doesn't do anything your problem may be in the computer or wiring.

Lovely. Well, just tinkering I pulled out my coil and set it in the freezer for about ten minutes. Put it back on while it was still cold and the jeep sputtered, started, then stalled. Try two-Engine started. Drive around, shut it off. No start. I'm taking it over to my buddies with a multimeter hopefully tomorrow-day after. Such a pain that the friggin thing will always run ok once it gets going I almost rather it just quit entirely.

With my Crank Sens disconnected, you're right-I no longer hear the pump run during cranking. Plug it back in and it comes back. The pump always runs during cranking, and priming.

What it comes down to is no (will have to verify this, but my plugs stay dry) fuel injector operation during no start periods, and weak or no spark during this as well. I also noticed that every once in awhile during the nostarts I will simply get one, good, strong spark followed by nothing. Still dying at 3/4 throttle, although now it seems to be based on load. Going uphill at 1/[email protected] it cut out, I let it off and it came back.

Sensors to test:
Cam sensor (I am highly suspect of this)
CPS although that seems ok?
Just going to replace the oxygen sensor.
Coolant temp sensor

Plus Ignition coil? Doesn't explain the no-fuel issue though.

I'm having similar problems and code p0320 and code p1398 on my 1997 ZJ. I'll try Thunder Chicken's approach it looks like good advice.

So I replaced the Crank Position Sensor (easier with some help) and that has fixed code p0320 and code p1398.

Danno said:

So I replaced the Crank Position Sensor (easier with some help) and that has fixed code p0320 and code p1398.

How did you go about reaching it. I'm having trouble even getting to it.

I used about 3 feet of extensions on a ratchet. I didn't lift the Jeep just lied under it. once you get the bolt off remove it. Replace it by leaving the paper spacer on the new CPS. This is when it helps to have two people. Have some one place a little pressure on the sensor with a stick. You then approach from underneath and tighten the bolt.