I have 83 f250 with 351w. The issue that I have is it will crank but no start, going through lot of trouble shooting including checking ignition switch, ignition module, distributor, coil, ect. The truck will start and run fine if I disconnect the starter solenoid exciter wire and use a bumper button

Any suggestions would be appreciated

 

I don't know how to get to this without trying to explain the way I see it.
If you are able to get the engine to run with the wire from the ign switch that energizes the starter relay disconnected ,possibly two conditions might exist,
One might be the switch is defective because it may be providing partial power to the starter relay, not enough to completely close the contacts yet enough to deprive the full voltage to the ign coil for the engine to run.
Has anyone changed the ign coil ?
Some coils required the full 12 volts to provide enough spark to run. Other coils required a resistor in the supply voltage to the coil that only required 12 volts for starting and then the resistor would drop coil supply voltage to 6 volts for running. I don't remember which coil they used in 1983.
Since the wire that goes to the starter relay comes from the ign switch and the engine will start with the wire disconnected , I would suspect a power supply problem at the ign sw assy. How are you checking these component out?

 

Thanks for the thoughts, first the truck will crank just fine with the oem wiring to the starter solenoid, I've checked my voltages at the coil both during crank and in the run position. 10v in the run, 12 during crank. There's a new coil that is for electronic ignition. Also a new ignition switch has been installed.
This problem has been an up and Comer, starting this past summer it started becoming harder to start to the point now, it won't start, originally I thought it just needed a tune up, but that didn't seem to help

 

What kind of quality spark is present at the coil hi tension wire and any spark plug when the relay wire is connected and when it is disconnected?

 

will check tomorrow, hadn't thought of looking at that

 

Checked the spark, with the exciting wire connected to the solenoid blue to a slight yellow both at coil and plugs, voltage at the positive of the coil 14.3 [Battery charger conected] with the exciting wire disconnected bright blue spark at both locations, with a battery voltage at 8.6

 

Now you have me puzzled. At no time should battery voltage drop below 12 volts unless starter current draw is taking place and even then it should not go below 9.6 volts. If it does there is a possibility of one of the following;
1. battery questionable
2. battery cables corroded internally or at terminal connections
3. Starter draw excessive (problem internal to starter assy)

 

With playing with it today, the truck runs fine with the could getting the lower voltage, as what is exposed to be pretty Ford and there wiring semantics. During the run, in the ignition switch, the power to the coil goes through a ballast resistor, witch drops the power down. It's get full Battery voltage when in the start mode of the switch. For what ever reason the truck won run getting full Battery voltage, I even tried using a separate power source, still. I honestly and rewired the ignition switch, and ran a new wire to the starter solenoid so the coil only gets the lower voltage

I'm going to give this a try for a while, being it's only I farm truck and doesn't see much road time, and see what happens. Thanks for the help, if you have any other ideas it would be nice, I rather fix things right, then half assistance them along