cherokee won't start when it's humid/rainy

[88 cherokee owner]

My Jeep has no problem starting when it's dry out, but when it's misty or foggy usually, it won't start at all. i usually have to wait until it's dry to start it again. I replaced the distributor cap, rotor, wires, and made sure the plugs were fine if that helps narrow it down. it also is a problem that only seems to occur once in awhile, but never when i am going for a fun drive, usually when going to/from work, so this is an issue. any ideas?

[AlohaBra]

Test..
* first for spark...if no spark...check the connector for the ignition module and other components
* look at condition and cleanliness of all igniton and fuel injection connections
* test, check, or replace crank position sensor if it has never been done

Aloha...enough for now...please reply to post...

[kmerian]

Never had that problem with my Cherokee, but I did have a 91 Dakota that would do that. Replace the plugs, or at least check the spacing. My problem was caused by there being too wide a gap between the electrodes

[88 cherokee owner]

sorry for not getting back very quickly, i had a lot of diagnosing to do. my coil tested fine, and so did the module that it plugs into (ignition module?). we also took a volt meter to the connectors where the coil plugs into - the positive and negative - and got a reading of 11.2 volts. the battery read 11.9 volts so there is some resistance there, but it is getting electricity, and more than 90% of what it should. we have tested to see if it is getting spark and the prelim tests show that it is not, so if that's the case it rules out the CPS because that deals with the injectors right? the new problem is that my vehicle doesn't start at all now. so whatever problem that i had before is no longer a short, but a full blown problem 100% of the time. let me know if there are any other ideas. thanks.

[AlohaBra]

As per your information:

Battery is weak...should be 12.6 volts...when cranking it must be over 9.6..that is called a load test.

Like K says make sure the spark plugs are "good".

And the CPS (crank or engine speed...sensor) does control ignition also.

[Dale Aeppli]

Check for spark at coil and plugs, CPS controls spark as well as turning fuel pump on. No spark, at coil check CPS. Dale [email protected] Also check condition of distributor cap and rotor

[88 cherokee owner]

allright, it wasn't the CPS i dont think, but it was close. it was the flywheel sensor, if that is the correct word for it. it is located on the backside of the flywheel up top. we replaced that and it fixed the problem. the old one had a bunch of gunk in it, so putting a new one in fixed the problem.

[AlohaBra]

Yeah...that sensor is called the CPS in the later manuals....called the engine position sensor on the earlier versions of FSMs.