I have a 1991 F150 4.9L engine. My question is. Can the camshaft break in that motor, and how will you know if it did? I heard a single thump sound while the motor was attempting to start (I just shut it off to put in coolant and tried to restart) and then it wouldn't start. Not sure what it is but need ideas. thanks!!

 

A camshaft actually breaking would be extremely rare. The distributor drives off the camshaft. You could check to see if the rotor in the distributor still turns, if it does and the camshaft broke it would have broken back of where the distributor is located.

 

I will check that. I did think about it but haven't looked into it as of yet. I just replaced the timing gear a couple of months ago and I hope that is not the issue again. I did hear
a thud sound when i was trying to start it and it sounded like something may have broken but have no clue what it could be or where to begin looking. It does have a strange pitch to it when trying to start it unlike anything i have ever heard before.

 

It doesn't sound good; but might not be too serious.
I'd suggest unplugging power to the coil while you diagnose. A small issue can become major real fast if the engine fires with a broken something in there somewhere.

 

Turns out that noise I heard was my started basically blowing up. Now I have to slide the transmission back to remove the pieces.