I'm working on a 1988 F150 with a 5.0 for my cousin.


He was going down the road when his power dropped and he noticed a gassy smell. He got to the next town and when he pulled into the local parts house, it died. He changed the spark plugs and distributor cap. He tried cranking it and the battery was marginal to begin with. The parts house tested it and it was shot. He put a new battery in and when cranking it, it would start when he put gas to it but it wouldn't stay running on its own. He smoked the solenoid so we changed that.


We pulled it to my garage and he had to go onto the next town for work.
I thought it might be the TPS so I switched it out. No go. I checked the MAP with a new one I had and that wasn't it either. I disconnected the battery each time. I know it has gas and spark. Every time I turn it over it cranks very slow.


Thanks in advance

 

If the starter has never been changed it might be time to consider replacing it.
The ideal procedure would be to do voltage drop testing to check the cables and starter, but if you don't have the meter to do that you might try the following;
put the headlights on and try cranking the engine.
If the lights don't go slightly dimmer there is high resistance in the starter circuit and all connections need to be cleaned. Make sure there is no corrosion in the cables themselves.
If the headlights go very dim the starter motor is drawing high current and needs to be replaced. It always a good move to check and clean the ground connections starting at right at the battery. The starter solenoid is mounted on the inner fender and uses the sheet metal for its ground, make sure it has not rusted and corroded where the good ground connection is required.