I have an 87 Chevy R10 with TBI on a 5.7L. Just aquired the pickup and installed a new timingchain. Been running great for 2 months and then the other night just suddenly lost timing. Could not get engine to start again till I turned the dist. almost half way around, even had to rotate plug wires to do this it had to be moved so far. Now will only run severly advanced, out of time at 0 TDC. I don't have a clue why this is, checked for slack in new chain and looks good. If anyone has any input on this I would greatly appreciate it. Thanks

 

pull the distributor out and make sure the roll pin didnt shear off on the drive gear. the bushing in the top of the dist might have started to seize from lack of oil ( crud build up blocking it) then it will shear off the pin and then grab ahold again when it smears some of the pin around. thats all i can really think of that coulda happened. it also drives the oil pump with that pin and a piece of something going through the pump can do it.

 

went to remove distributor today and put everything I changed back and set to 0 TDC. when I removed the cap the rotor was right where it should be. if the crank key or roll pin sheared it should be in the wrong place, seems logical, right. Is there any way a pickup coil could cause this?

 

Tt turns out it was just the ignition coil. Thanks for the responces and this helps someone else.