98' 4.0 aw4

I noticed last March that my jeep doesnt like to start (only first start up of the day) when it is cold and damp out. It sounds crazy but when its 33-45 out and really damp, it cranks and cranks not wanting to start. Usually after re cycling the key, it starts right up.

No problems during the summer at all, no problems after it has been started during once for the day.

Today I popped in a new MAP because I had one laying around. I noticed the jeep seems to run quieter with the new map in it.

Can a wonky MAP cause a no start, or slow start?

 

The usual suspect for this description (only when atmosphere is damp) is secondary ignition. Which means tuneup hardware. When is the last time yours was changed?

Fresh Champion copper plugs gapped to .035, new plug wires, cap and rotor with brass contacts will go a LONG ways towards ensuring quick starts.
I'd start there.

If you have an extended crank time the first time you start your XJ no matter what the weather, you could have a check valve in your fuel pump assembly starting to fail. That results in a drop in fuel pressure and it takes a number of cranks to build up enough pressure to fire the engine.

 

Plugs, wires, rotor all less than a year old.

Belden Eichlen all the way around, champion plugs.


Ill pull the plugs and check the gaps again, I set the gap when I put them in last year.

Its puzzlng lol. I just took a drive with the new map and it idles smoother and takes less throttle to hold/get up to speed. Nice all on its own as I hope i get my fuel milage back to around 17-18 instead of 15-16.

 

Is the cap cracked? Another thing to check is if the cap it sitting secure and flush on the top of the distributor. If it is not on securely, moisture can give you issues when it is damp.

 

Good point, Ill check that in the A.M.

Thanks for the response.

 

Along the same lines, on one of those cold damp mornings, you might pull the cap and check for condensation inside. I have a place in the damp Redwoods and have seen that allot. For years I've called it "RNS" You might have Rio Nido Syndrome!