I'm chasing a gremlin in my '88 F250. It's giving me hard start issues related to the timing and I noticed tonight that when I remove the sprout and check the timing, the timing light gives me a nice regular pulse. When I reinstall the sprout and check again, the timing light is all over the place, sometimes not light up at all for a second, then rapid flashes...no rhyme or reason. Is this a behavior I should be expecting or a sign of a failing part?

 

Most timing lights will do that
Your truck is not missing like crazy right?
But yes the timing jumps all around and can go to 60 degrees at times and most lights can not keep up
Even my snap-on digital advance light has trouble
You just make sure it is at 10 with the spout unplugged
Then let the processor take over
And if it is miffed and you have big trouble with the spout plugged in, your processor may need to be replaced
Check the codes with an old star tester or better yet a super star 2 or NGS
Good luck

 

SPOUT not sprout. Yes the timing should be jumping around with the SPOUT plugged in.