I have an 81 f250 that originally had the 4.9 in it but was swapped with a 6.6 that I believe is from the 70s. I had this engine running not too long ago but now all I’m getting is a single from the solenoid and sometimes the starter. So far I have a new battery, solenoid and starter and still I get the same thing. Me and my friend found if we grounded the side of the solenoid that goes to the starter a little more juice would get to the starter but it still wouldn’t turn over. Any ideas on what this is

 

Hello, and welcome to the forum.

Are you talking about grounding the case of the starter relay, the big doohickey on the inner fender just aft of the battery? The actuating coil (electromagnet) of the starter relay is grounded via the case, which in turn is grounded via the inner fender. This ground path was marginal at best when new, and often deteriorates over the years. Not sure exactly how you grounded it, but for troubleshooting I'd run a jumper from the starter relay case to the (-) battery terminal.

After that, read this long-winded treatise about troubleshooting a slow starter. This will absolutely, positively pinpoint the fault. Three quick hook-ups with a voltmeter and you're done. Your wallet will thank you:

https://www.ford-trucks.com/forums/1...w-starter.html


Make sure your battery is fully charged before beginning any troubleshooting. Even if new, most batteries are not fully charged at the time of sale. I highly suggest hooking up an automatic charger overnight, something with at least a ten amp output. A trickle charger won't cut it.

Also, please be aware some aftermarket starter relays are junk, right out of the box. Even though you've replaced it, test it as detailed above with the voltage drop test. More details here:

https://www.ford-trucks.com/forums/1...i-mean-it.html

 

that is exactly what I’m talking about and I will try everything you have said thank you very much.