Yesterday I was trying to trouble shoot a rough idle problem on my '80 f150 302. It would start fine but acted like it was missing on one cylinder, so I was pulling one plug wire at a time at the distributor and restarting to find the one that was missing. Well, in the middle of this my father-in-law showed up and started helping... yeah right. Anyway, instead of putting the wire I had pulled back on before pulling the next wire, he pulls wires off and screwed up the wires! OK, no problem, just pull out my manual... look up the firing order and put them back. Well, I pulled the wires put them back in the 1-5-4-2-6-3-7-8 it showed in the manual... Tried the starter... nothing! It acted out of time, popping and sputtering... wouldn't fire or run. Then I thought maybe since the guy I bought it from had the motor rebuilt it could be using the 302HO order...1-3-7-2-6-5-4-8. So I try that, same thing or worse back fire through the carb! Then I notice the firing order cast into the intake, it's the 15426378 so I put it back... So I think, well maybe the distributor is installed out of time... so I re-align the timing marks and check the rotor position... it's lined up with the #1 cap point. What is going on? It use to run, not great, but it would at least start and was driveable. Now I've got nothing.
Help!

 

Did you remove the distributor at any time? Was the plug wires removed from the plugs? Put the rotor pointed to #1 and remove the plug from the passenger side, front most forward cylinder (#1) and see if the piston is TDC, if not then your distributor is off.
It definetly sounds like your timing is off somehow.


It's been a while since I looked at one, but is it possible for the cap to be put on reversed, say #1 marked on cap is actually on #6?

 

I have a early model 302 and went outside and checked how my firing order is just to be sure. If you give me your e-mail I can send you my diagram for the firing order on my truck.

 

It took a lot of head scratching but I finally got it figured out... It seems the distributor is off by 180 degrees.
The guy who rebuilt it must of hosed it up during the install. The vacuum can on the distributor falls between the ac bracket and the radiator hose. This limits the amount I can twist the distributor for setting the timing... so I resorted to indexing the plug wires backwards one place. This put the whole assembly in a position were I could set the timing by engine sound.
Needless to say I somehow fixed/found the missing cylinder with all the switching and pulling on the wires. The engine now runs like new... I had to remark the cap so I know where the #1 wire goes. (it's off by three holes!)

Now if I just leave it alone it will be fine...

 

I was just about to ask if the dist. could possibly be off by 180*. The truck would run, just not very well. Glad you got it figured out!!!,,,,,98