I just replaced my distributor with a remanufactured unit from Napa and while doing the job I came across a problem that I don't quite understand. Let me explain....
On the old ditributor I had replaced the wiring connector and it's mate on the wiring harness years ago out of necessity. The old connector had become brittle and broken so I replaced with a nice late model 3 pin water tight connector I salvaged from the wreckers.
When I installed the new distributor, I initially used test leads to mate the distributor to the wiring harness and then set the timing up and the engine ran great. I did this because I wanted to make sure the new distributor was ok (in case I had to return it) before I cut of the factory style connector.
Once everything proved to be ok, I went ahead and cut off the original style connector off the distributor and spliced in my newer style connector to mate with the wiring harness. When I was done and started the engine it ran terrible, barely idled, stalled and back fired when I gave it even a little throttle. I checked the timing and it was very erratic, jumping all over the place??

After pulling my hair out for a while I realized that I had reversed the polarity on the pick-up coil! Out of curiosity I re-installed the old distributor and mis wired it on purpose, it behaved the same. I hadn't paid much attention to the polarity , after all, it's just a coil. Shouldn't matter.

So my question is what gives? Is the pick up coil more than just a coil? I checked it with an ohmmeter and saw no difference in polarity readings? Is it more of transformer, which depending on winding placement in reference to ground might explain things. Does anyone have a schematic of the ignition module that I can look at to see If I can make sense of things.

Long story for a simple question...but I just can never leave well enough alone!

Thanx,
Frank

 

Not sure what you did, but here's the number in case you need to buy one.

D4PZ-12A112-A Pickup Coil (Motorcraft DU-1-A)

 

As I recall reversing the coil wiring will throw the timing way off.

 

Thats for sure! but without a schematic of the control module I can't say why for sure. I suspect that reversing the polarity may change how the ign control module interprets the pulse's from the distributor. Instead of positive going pulses to trigger a spark, the pulses would now be 180 degrees out of phase or negative going pulses. So the ign. control module would trigger a spark in between pulses instead of on each pulse. The spark duration would be longer and sort of overlap some of the timing which explains why it would run at all. At least, thats the best I can come up with without looking at a schematic of the ign. control module. Remember this was 1976, there are not a lot of smarts in the module.

Way too much electronic theory! but enquiring minds want to know!

Frank

 

Maybe Try the electrical forum.

This really has nothing to do with a 73-79 truck ...just ignition

Franklin will help you out.

Check in my gallery at the bottom "the 80's" album. the module info is in there

 

Thanks Dennis, I couldn't get the images from your gallery to a size that I could read them clearly.

 

The differane is in the primary winding and the secondary winding. the pick up coil makes a magnetic field and is broke by the star wheel on the dist. shaft, so if you power the wrong side of the pick up coil the magnetic field will be all wrong and give the ignition module the wrong info and it will run like crap if at all. Hope this helps a little, Jesse.

 

http://www.clubfte.com/users/mil1ion...estcloseup.JPG