I did pull the plugs when I ran the compression check. They were wet and black. The truck is actually backfiring through the carb and burping (not backfiring) through the exhaust.

 

Wet plugs indicate we got fuel and no spark. I'd try the jumper wire and see if that gives the coil enough voltage to light 'em off.

 

Bad coil? That can really mess things up.

 

pdqford,
Thank you for all of your help with this. I will try a jumper tomorrow.
460me,
I was curious of the coil. It is fairly new, but.... how do you check a coil?

 

To check the coil, measure the resistance accross the coil's primary terminals with the coil disconnected to check the coil's primary winding. I don't have a spec but it should be in the .5 to 4 ohm range. Anybody have the spec for this? Also check the resistance between one of the primary terminals and the secondary terminal - should be in the 5k to 20k range.

Additionally, you should check for grounding of the coil's primary and secondary windings to the coil's case. Connect one ohmmeter lead to the primary terminal and the other to the case. Then connect one ohmmeter lead to the secondary terminal and the other to the case. Both of these readings should be O/L (infinite).

If the soil fails any of these tests it is suspect. But if it passes it doesn't guarantee a good coil. Further testing under load with a scope would be necessary.

I'm thinking that the 5.1 volts at the Batt coil terminal with the starter relay disabled is way low. And probably when the starter is cranking that voltage probably drops to maybe 3 volts. I don't think that is enough to jump the gap of the sparkplug. It might through a yellow spark in atmosphere, but under cranking compression it wont have enough voltage to through a spark through the compressed mixture.

 

I have pics

http://www.fluke.com/application_not...AGID=1&SID=103

 

I tested the coil. It is an MSD. I also tested an old Ford coil and the ford coil on my F350(which is running).
MSD: primary is .9 with meter set at 200ohms, secondary is 4.5 with meter set at 20Kohms.
Ford: primary is 1.8 with meter set at 200ohms, secondary is 13.4 with meter set at 20Kohms.
Ford on my F350: primary is 1.7 with meter set at 200ohms, secondary is 17.2 with meter set at 20Kohms.
Now I realize the MSD looks weak, but all three coils will start and run in the F350.
Also, with the Ford coil in the F100(problem vehicle) the batt terminal of the coil with the key in on/run is 6.8 volts. The MSD is still maintaing 5.4.
I bet you guys are ready to throw in the towel on this one

 

Don't MSD coils require 12 volts ?

Ford coils require a ballast resistor to reduce voltage to 6-8 volts.

Try the jumper wire from the battery to the + coil terminal and see if it will fire.

 

Mil1ion! You da MAN! (Again)

And Thank You for those coil specs.

(Me does think that Fluke has a typo on the last line of the picture's description. It should read 10K ohms, not 10 ohms.)

 

I connected a jumper from the battery to the battery side of the coil. I am using the Ford coil. I got a backfire from the carb. Tried some adjustments to the timing and now nothing. I pulled #1 plug, grounded it and kept the jumper from the battery. The spark is yellow to clear. The Ford coil seems to be in spec, buying a new one would seem to be a long shot. What now? Thanks again by the way.

 

The MSD has lower resistance in the primary which allows the primary to flow more current - potentially more voltage on the secondary side.

Whoa! That is now within spec? That's about what it should be when running through the ballast resistor. Give that wire and connection the old wiggle test while monitoring the voltage.

I figured out why the coil Batt terminal is low during Start/Crank (should be within 1.0 volts of battery voltage) with the starter relay disabled. I made a boo-boo Even though Mil1ion's diagnostic procedure says to disable the starter relay (step #3) during the Start/Crank test, but that is only if your starter relay DOESN'T have an "I" terminal. After tripple checking my Ford wiring diagram I noticed that it shows the source of the full 12 volts during Crank/Start is the starter relay (not the ignition switch). So if you have an "I" terminal on your relay, by disableing the starter relay we wont get the 12 volts from the relay during the Start/Crank test, but we'll still get the 5.1 volts from the ballast resistor.
That resolves that issue. You could run the Start/Crank test with the starter relay connected so the engine will crank and read the Batt coil terminal's voltage while cranking, just to verify it.

And now that you read 6.8 volts with the key in the Run/On position, that is within spec. Now I'm back to . . . . I don't know!

 

Okay, summing everything up so far.
All of my voltages and resistances are within spec. My compression is 155 to 165psi (valve train should be good). I have set the timing to 10* btdc at cranking speed. I have fuel. The yellow spark?...could the plugs need to be replaced? All of the plug wires are good. This engine was running very well before I started the change in the mechanical advance. I have tried a completely different distributor as well. I am positive that the timing is not out 180*. I have tried a different ignition module and a different ignition switch. I have tried direct battery voltage to the coil. If the direct battery voltage to the coil (within specs) still produces clear to yellow color at the plug, would that warrant plugs?

 

I tried to check the spark color on a set of extra plugs I have. The color is definately yellow. Then when I connected everything back together and I turned on the key to try and start it. Turning the key to on/run it backfired through the carb. I did not try to start it, I turned the key off and then back to the on/run position and it burped (not backfire) through the exhaust. Will setting the timing with the cranking speed of the engine get me close enough for the engine to start if everything else was normal? If not should I go more advance or more retard. I know it seems that this is timing, but how do I get a better baseline. This is not my first distributor install. I have re-installed this distributor probably over a dozen times and had the engine fire on first try.

 

This is not right! As a matter of fact, I just found the following in my Ford Shop Manual in the ignition diagnostic section:

"Cycle ignition switch form "Run" to "Off". A spark should occur each time the key is turned to "Off".

The transistor in the ignition box should only turn the coil current off when it senses the magnetic field of the pickup module. Or the current will be turned off if you turn the key off. Either one should cause a spark.

Since you tried a different ignition box, that should eliminate the transistor. Only thing that hasn't changed is the wiring harness and your grounds. Could your ignition switch be wired wrong? Or a short to power in the primary side? I'm stumped and guessing . . . .

 

I dont think the ignition could be wired wrong since everything was working well prior to the distributor changes. I am going to pull the harness and ignition module off of my F350 and give it a try. Before I do that, is there a way to test the ignition module. My most curious thoughts on this is why is it backfiring through both intake and exhaust? Also what would cause the yellow spark? I thought more people would have responded to this. I must really have everyone stumped. I really appreciate all that have helped with this.