I have a 95 4.9L with 257k miles. Lately the truck will turn over but sometimes it wont start. Other times it will start no problem. Last week I pulled a sparkplug and wasnt getting any spark so I replaced the ICM and coil but it still wont always start. The truck wouldnt start today so I hooked a spark tester to the coil wire. When I turned the key there was one spark and then nothing. It finally started after many tries but wouldnt start again once i turned it off. Sometimes I got spark after two or three tries or twenty tries. Once the engine starts it runs fine but if I turn it off not sure if it will start back up first time or not. Looking for any ideas. Thanks.

 

My guess is you have a bad or cracked coil. But don't go out and buy one on my word, see if someone smarter than me chimes in.

Also might want to remove, clean, and tighten any and all grounds you can find.

 

Did some more research online, found several posts with the same problem. Most of the posts pointed to the PIP sensor in the distributor. I put in a new distributor and the engine starts every time now...problem solved