Hi all,

I have a 1988 ford F450 flatbed dump that I use for home landscaping projects. Lately I have been transporting a lot of dirt to a friends place as he wants it and I don't. So it has been a good arrangement.

A couple of weeks ago I cut off the intake air horns as per several posts recommending that, put in a new ignition module which attaches to the side of the distributor, and advanced my idle ignition timing to 12 degrees BTDC. These changes seemed to help but after doing this I did notice a sharp smell of burnt Nylon which I attributed to the Cat since my exhaust was probably running hotter due to the advanced spark.

Anyway, today I had just dumped a load of dirt and was traveling up a moderately steep grade to get to a gas station when my truck slowed and started to make a noise like the muffler dragging the ground. I had no throttle response so I pulled to the side of the road by which time the engine had stopped running. I looked under the truck and saw no loose muffler, no driveline problems, and no unusual oil leaks. So I popped the hood and everything looked fine there.

I let the truck cool for ten minutes and tried to start it and it sounded normal but would not start. Once in a while it would backfire loudly but would not run.

What do you think is wrong? Two ideas I have is that the ignition system pretty much gave out, or maybe the timing chain jumped a tooth or two. The engine has only 30k miles on it as it was taken from a later model truck in a wrecking yard.

What do you guys think is wrong with it?

Randy

 

As for the timing advance, I think you're "ok" -- some can go as high as 17 (without pinging themselves to death), others can only tolerate 2-3 degrees.......I wouldn't think a motor with 30K would have a timing chain so worn out that it "jumps" a tooth or two.............

What brand of module did you use (it may be an "infant mortality" type problem)??

 

Do you still have the old ignition module(was it bad or still good). Why did you replace it in the first place. If it was still good then try putting the old one back on.

 

Okay, so here is what the problem was and I am a little embarrassed. I had the tow truck drop off my truck at a local repair shop and what they found was very simple. The rotor had been arcing so badly that at least 1/8" had been burned off of the metal tip and even the plastic holding the metal in place had been charred even more. Hence the burning Nylon smell. I have never seen a rotor so trashed. The heat generated by the long arc eventually softened the rotor so that the metal element flew out and then my truck stopped.

What would cause the rotor to burn away like that? I think I probably replaced it and the cap when I did the engine transplant and that was only 2,000 miles ago, if that. Even if it were the original rotor and cap it would have had maybe 32k miles on it. Very strange.

Randy

 

Do the EFI engines have a condenser on the coil or distributor like the DSII ignition engines did?
Did your mechanic check the distributor shaft for wobble?

I've never seen a rotor as badly scorched as you describe!

 

No condenser on efi motors, but I have heard of the occasional rotor going bad. Shaft wobble could be a likely culprit as well.

Check for play in the dist. casting. There should be no more than a couple thousandths.

Did you remove the spout connector when setting your base timing?

 

Yes, I removed the spout plug when I set the initial advance. But then the shop set it back to stock specs so now I have to do it again. I will check the dizzy shaft for wobble and check the rotor after a few hundred miles. I have never seen a rotor in such bad shape. I suppose it would make sense to pull a couple of plugs to see what they look like as well.

Randy

 

I'm less inclined to think mechanical wear (given the low mileage) is the culprit, but from an electrical point of view, high secondary resistance in the ignition circuit (excess impedance in spark plug wires wires, wider than spec'd spark gaps, etc) can cause voltage "spikes" and higher than normal voltages.............such condition could, in fact, lead to arcing and the toasted rotor you've experienced..............

 

Hey, if .045" is good - .065" must be better... right?