1979 f250 4x4 with 400m motor wont stay running when I let off of the key. I have been messing with this all day. I jumped the coil over to the b+ terminal thinking I wasn't getting power from my resistor wire. Still does the Same thing. I have 12v to my coil but it wont run unless I keep key switch in start position. What am I missing?

 

 

I can do that what pins should I have power?

 

Quick and easy troubleshooting: Pull the three prong spade connection from the distributor.....and clean both terminals.

Measure the resistance between the ORANGE and PURPLE connections. You want to see between 400 Ohms and 800 ohms. The BLACK wire is an ignition ground.

I omitted a coupla before-hand tests because I think the stator went south. If the resistance is in spec, we'll check/replace the ICM.

 

615 ohms between orange and purple. Do I have ground on that wire only when ignition is on?

 

Also I have no ground on black wire in on position.

 

I knew second guessing myself would come back and bite me in the butt.
Anyway.....the stator checks out good....and back to basics.

Connect a test light to the (-) TACH TEST terminal of the coil and the other end to a good clean ground.

Have a helper crank over the engine...you're looking for the test light to "blink" when cranking. If it blinks, the coil is getting switched and the ICM and stator are good. But you knew the stator was good anyway. If you have a "no blink" situation, the ICM or coil is pooched...meaning the coil is not getting switched.
You could check the impedance on the coil, too. You want to see ~1.3 Ohms on the primaries and 8 k Ohms - 11K Ohms on the secondaries.

If you have a test light blinking when cranking, and the coil's resistance checks out ok, the only thing left is the ballast resistor wire. To check it: Key ON, Engine OFF....measure the voltage from the coil's (+) BATT terminal to a good ground. You want to see ~ 5-8 VDC.

Too much info? Please excuse..but these tests will be conclusive.....I won't venture a guess this time - don't want it to come back and bite me a second time.....hehehe

 

Other things to check from the gate:

Disconnect the 2-terminal connector at the ignition module. The RED with BLUE stripe wire coming from the TRUCK (would go to the WHITE wire of the module) should be hot with the key in START. The other wire (WHITE) coming from the TRUCK (would go to the RED wire of the module) should be hot with the key in RUN.

 

The BLACK wire coming from the TRUCK should have continuity with ground (no more resistance than that of your meter leads)......when the 4 prong connection is separated...and cleaned.
As should the BLACK wire at the three prong connection.....those are female connections so be careful, and make sure they're clean.

You should have continuity with ground whether the key is on or off.

 

I have power to the module on both wires. I also have power to the coil. In both start and on position. I am super stumped and don't have anymore time to spend on it before I head out of town. I might look at it more in a month or so.

 

Ok, that leaves the ballast resistor wire...did you check the voltage with the Key ON, Engine OFF? You should have BATT voltage in START only.....

Well, remember to check that wire AND the coil when you get back. We'll be here......

 

If I bought an msd kit for it would that fix my problem assuming I install it correctly?

 

Save your money, listen to Filthy Beast and he will get you thru this way cheaper than a MSD kit.

Subscribed, so I can save all of FB's trouble shooting steps.

 

I kind of suspect the ignition switch. You could get it started with the starter cranking, and then have an assistant pull the red wire off of the "S" post on the Fender Mounted Starter Relay to stop the starter, and see if it stays running with the key held to start.

 

Solenoid wires swapped? Ign on S, and S on Ign? Does it start turning over as SOON as you turn the key? Sometimes its simple things that get missed or swapped.