Why would a 1999 Suburban start then shut right after a few rainy days?

Answer 1

Your security system is malfunctioning and putting your Suburban in a temporary lock down. It is shutting down your engine right after start each time. In a few hours it will reset and allow you to start your Suburban again. Needs a new distributor cap. May be a loose fuel pump electrical connection. Located on top of the fuel tank. Requires dropping the tank to access and inspect.

Answer 2

Could be multiple issues here, but it will end up with one result...an exposed ignition component. Could be that water is somehow leaking around the hood and dripping down onto and around the distributor. That would definitely cause an issue. Could also be down by the starter, although less likely.

Does this happen after you've driven it in the rain, or when you first start it on a rainy day? If you've been driving it around and then it won't start, more than likely the water is from the road and splashing up, which would point to the starter/solenoid. If it's happening first start on rainy day, it's probably the distributor. If it is the distributor, it may very well have a crack in the cap. They're cheap to replace and might be a good spot to start.

Adding to this on the first start of the day after it's been raining; I have had the same issue for over a year after replacing the dist cap and rotor, ignition module, coil, MAF sensor, crank postion sensor, greased every connection under the hood and still had the problem. Ended up being that I was not tightening the dist cap tight enough. When you get a new one, and I would suggest a GM one for a better fit, the screws have a coating on them to keep them from backing out. This coating will give you a false feeling that the cap is tight when, if you move it on the distributor, it will still move slightly. This slight movement is just enough for moisture to get into these highly sensitive distributors and keep them from firing properly. Tighten the screws until the cap is tight on the distributor. You will really have to crank on them to make it this tight but be careful by checking it after every turn of the screw to not crack the cap. I know this sounds too simple but I was ready to take mine to an auction to get rid of it until I did this and cured the problem. Good luck!