I just inherited a 1980 F100 that has been parked for 4 years. The last time it was started was three years ago and I was told it would run fine, all it would need is a battery and a clutch. I put in a new battery and starter relay. I changed the oil and put a little marvel mystery oil in each cylinder. The clutch adjustment rod has been disconnected in preperation to remove the transmission. There is a lot of rust on the battery cables, but I can turn the lights on so I know there is current flowing. My problem comes when I attempt to crank the truck. The battery light will be lit until I turn the key, then there is a thud and all electrical will turn off. I hope I do not have to remove the engine, but any advice will be appreciated. Thank You.

 

Could be just the starter is hung up from sitting , I would try turning the Engine over by hand, put a socket on the big bolt in the center of the bottom pulley( Crank Damper ) pull the coil wire just to be safe !!!! An it should roll over its going to be tight . Would be easier to pull the plugs no restaince then turning the eng . If it turns ok , Then I would say you got a bad starter. those ole Ford starter are easy to rebuild , Also you can get one from most discount auto part stores for less then $30.00 bucks. Another ole trick , is get about a 2 pound hammer an tap the starter case a few times while you have someone crank the motor ( JUST A TAP DONT RUIN THE STARTER BEATING ON IT ). You said there is a lot of rust on the cables , The starter draws a lot of juice so the cables have to be clean , an tight cant tell you the number of times I have gone out for a no start only to find I could twist the cable a 1/4 turn an lift it off the battery .. Other wise your just spinning your wheels.or in your case NOT .

 

Oh yea one more thing I forgot , you said the clutch rod was off , I cant quite remember on the 80's , but I thing you had a safety switch on the clutch pedal, that had to be pushed to start the truck !!!!!

 

All thats a good idea, but I bet the cables should be replaced. I'd have a starter/alternator shop build me some new ones.

 

Now you said you put a little MMO in each cylinder , did you pull the spark plugs an add it ???? Any chance you might have a hyd. lock ???? You might have to pull the plugs back out an spin the motor over to remove the excess oil .