So while I've been battling a misfire, I've never had any problems with the truck not starting right up. I went to let it run a little today and it wouldn't start at all. It kept trying to turn over, it sounded much like when I was priming it on the first startup after the HG job.

I put an inline spark checker and it didn't appear to have any spark. I think I've read that a cracked windshield cowl could let water right down the back of the engine where the coil packs are located. Is that really a possibility? Or is there something else I should be looking at?

 

Probally a knock sensor

 

Well I let it sit another day and tried to crank it up again today. It started right back up. It had to be something to do with moisture, and since my Disco sits outside uncovered I need to figure out what would cause this.

I'm not familiar with the knock sensors, is that something that is vulnerable to moisture?

 

I would also look into the Crank Position Sensor. It sits down kind of under the coil packs, and could certainly get wet if water were running down the back area of the engine. I had an issue last week where an oil leak got to the crank position sensor and managed to work its way to the tip of the sensor itself. It caused the truck to go into limp mode every few miles until I removed it and wiped it off. I believe that sensor will allow crank but no spark if it's damaged or broken.

 

Ahh yea I recently replaced that sensor last year, but it makes sense if it got wet.

 

Its seems like its definitely moisture. I remember the time I had that issue every time its rained. Especially when running over street water and when it hits the manifold, steam goes up, seems like it gets into the coil pack behind and it will run sluggish until it dries up. I would suggest to get it tune up again if you are having a misfire. Do not use any grease in the rubber boot on the coil packs since vibration will get it loose. The rubber boot will seal itself around the coil pack chimney plugs and you want it tight and permanent fit. I would also suggest to relocate the packs if you get a chance for easy misfire maintenance.
I doubt about the knock sensor since mine is not connected.