Spark drops out????

[chasman55]

96 F-150 300 six, why would I loose spark from the coil / I replaced the coil, checked all connections, sometimes it starts right up runs great and then dies, no spark from the coil???? any ideas?

 

[95F350XL]

Usually when that happens its the control box. Should be on your drivers fender under the hood spring. There will be an aluminum heatsink, with a grey plastic module in the middle of it.

 

[Old_Paint]

Does sound like the TFI, but usually those have two failure modes. Either DEAD, no spark, no crank, nada zip zero zilch, or runs perfect until it gets hot, then shuts down. Are you having problems with no start after it shuts down, or only with it shutting down while running? If it's dropping out while running, but cranks right back up even while it's hot, that sounds more like a bad connection in the ignition switch, and will be a lot cheaper to fix.

 

[chasman55]

I replaced the control box and ignition switch but still have the problem, after it stalls it does chank over but has no spark from the coil, when I jump the solenoid a few times I'll start to see weak spark and then it'll start and sometimes it will run for an hour or shut down after running for a short time???? I'm stumped!