I have an 85 F150 that will not start. I took the coil wire off and put a sparkplug in and it only sparks (one spark) when I let off the key after cranking. I have replaced the ignition switch, ignition control module, solenoid, and the coil. Has anyone experienced this or know what might correct the problem? The truck is getting fuel like it should, just no spark while cranking.

 

Have you tried to check if your getting voltage to the coil with the key in run postion and crack postion. sounds like your not getting voltage to the coil while cranking.

 

When you say you replaced the ignition switch, do you mean the switch at the bottom of the steering column? That would be my first guess at what the problem is. The replacement switches come with a pin to hold them in the locked position. After adjusting the switch location you must remove the lock pin. If you have already done that then my guess would be either a bad ignition switch or it is out of adjustment. Hope this helps. This is a pretty common problem with that year truck but a new switch usually takes care of the problem. Gil

 

Yes, I replaced the ignition switch on the steering column. I even tested it in a variety of positions to see if for some reason it was installed wrong. No change in how the truck acted.

 

I do have power to the coil in the run and crank positions. The only ignition components I have not replaced are the regulator and the distributor.

I am at a loss as to what it could be.

 

Is the spark a white/ blue color or a red orange color?

You may want to try and post this in the electrical forum.

 

you could have a bad pickup coil in the dist you can check it with a ohm meter to make sure it's not shorted out or broke circuit, that will cause it to not tell the coil when to fire but you will get one spark when you kill the power to the coil by cutting the key off.

 

replaced distributor, cap, rotor, plugs, and wires. fired right up. set timing. runs great

 

betting you had a bad pickup in the dist causing your problem then. really not that uncommon and glad you got it running.

 

I had A85 F250 with same problem replaced modual worked fine for about 2 weeks then back to same condition and found that there was an intermetint short right at one of the plugs that goes in to the modual.

 

as i said, that problem seems to be fixed but now I have a problem with the truck bogging down when I press the gas pedal. I can let it idle or I can floor it wide open and it will go but normal driving it bogs down. Could this be a timing issue or more likely a fuel issue?

 

Make sure your vacuum advance is working correctly.

 

On my '85 I had a similar issue with it bogging down (and sometimes dying out completely) at partial throttle. Found out it was the fuel bowl float levels that were set too low.

It wouldn't hurt to check that on yours.

 

I am in the middle of the TFI to DS2 swap and am having the same problem. I am using the TFI coil. I have power to the coil during crank and run. Pickup coil in the distributor is brand new. Coil and ignition obviously are good, as I drove it into the garage. Swapped the ICM off of the wife's Bronc and have the same condition. I would have swore the pickup coil was bad, so I replaced it. Again, the only spark I have is when you let off of the key. Any ideas?

 

Check all the wires and connector pins in the harness between distributor and module and coil, especially the grounds, for an open circuit. A broken wire right at the back of a connector pin is fairly common. Use the old pull and wiggle test. Also make sure none of the wires are rubbing against the engine block or other ground.