Hey all, I recently bought a 1987 F250 4X4 Extended Cab 460 Auto for cheap. The guy I bought it from said it just stopped running one day and that he figured (somehow) that it was a spark problem. When I got the truck the engine was taken down to the timing chain which was replaced and not yet run.

I put the engine back together and diagnosed that no fuel pumps work (which I assume was his original problem). I replaced the front tank's pump and it is working as it should now. All I get when I turn it over is backfires through the carb. It wants to fire right up, but backfires and I obviously stop cranking.

I double checked my timing. Cylinder 1 at TDC, balancer where it should be and the rotor is pointing at #1 plug wire. I then triple checked my firing order from the intake and added electric grease to both ends of the plug wires. It does feel like it wants to start right up but backfires through the carb.

I guess what I'm wondering is if there is anything else that can cause this other than what I suspect -- the timing chain being off a tooth. What else would you all check before tearing the front of the engine off again?

 

A weak coil could cause backfire/ no start issues.

 

Really? A weak coil? I could ohm it out and see where it's at. Interesting, thanks!

 

TDC comes up twice once on compression stroke and once on exhaust stroke make sure you are on the compression stroke sounds like you are 180 degrees out of time.

 

It's possible. I held my finger over the plug hole until air blew out of it which would happen on either exhaust or compression stroke. Any easy way to be sure I'm on compression?

 

don't just hold your hand over the hole, plug the hole with your finger and you will know if your getting compression or not. Also have you checked the whole engines compression?

 

I have, yeah. The lowest cylinder was 155 the highest was 180. Decent enough for how neglected this engine was. I'll try again with hopefully better results.

 

Please delete