hi there all. 78 f250 400 cid. when i turn the key in the ignition switch to the start it turns over and starts,the key then returns to the run selection and everything is fone. but alot of the times when i turn the key to start selection it turns over fine but does not fire until the key is turned back to the run position. would this be a problem in the ignition switch or could it be a problem in the starter relay or somehwhere else?when it did it today the truck runs but kept konking out every so often just like if i turned the key off while i was driving,but i still have electrical power to the radio,lights etc. it fires right back up again though but its a real pain in the #$% .

i would appreciate any help. thanx

 

I would unplug and check everything related to the ignition. Check and clean:

The connectors going to the ignition module

The ground connection inside the distributor

The connector on the coil.

You may want to get it running, and then wiggle the wiring around a little to see if you can get it to cut off.

 

hi all. i traced the wiring and the 2 wire connector coming from the ign $ to the module was falling apart so i cut it out and spliced it to together. nothing happened.start would work but wouldnt run,switched the red and white and now it runs. i have a duraspark i think. it has 2 wires from the ign switch and a wire from the module to the dist and coil. i just have a few questions. if the wiring was reversed in the first place why would it have run? im guessing ti was shortin out in the connector but i would have thought it would died and that would be it.
the other question is should i have 12v at coil+? or should it be less? should i add a resistor? i also have 12v on the coil neg but i thought it should flucuate while running. my multi meter is a fluke so that should be alright. thanx for the help again. i have learnt alot about the electrical system these past few days by going through old posts. funny how many problems are the same. its better than just replacing parts by guessing.

 

You should have a little less than 12 volts on the coil positive.

The red wire has voltage when the key is in run.

The white wire only has voltage when the Key is in the start position. This would explain why it would start but not run when the wires were switched.

Your original problem may have been a loose connection for the red wire. It's more important than the white wire as far as running.

You can't see the fluctuating voltage on the coil negative because it's too fast for the meter to respond. You would need an oscilloscope to see it. The meter is just averaging out the pulses and giving you 12 volts.

 

cool. thanx franklin for the help. hopefully everything is good for a while now. the ignition box and distributor is over 12 yrs old now so i cant complain even if it did die.

 

I Marc, glad to see other's show up on FTE from Central Alberta.

Let me know of you want an FTE window sticker.