Hey guys,

Have ignition issues -truck shut down, found the wire to the negative terminal on the coil making contact intermittently, worn through at the terminal. I replaced the coil terminal clip and thought I had it but the truck will shut down while driving at times, passing fuel into the muffler and backfiring. So far it starts right back up. It seems to run fine until you drive it and shut it down, go into where ever you were going crank it back up, drive a few minutes and it cuts out.

I checked the wiring at the ignition switch and throughout the rest of the system and haven't found anything that sticks out. I pulled the distributor cap, rotor and spacer to visually check the pickup and found that it is loose. Looking down on it, it appears that it is secured by two posts and it rocks back and forth on the top one, swinging away from the distributor shaft. Is that normal or should it be rigidly mounted?

Any advice?

 

The pickup should be firmly attached to the upper plate. The vacuum advance arm should be able to rotate the plate some, but in a circle around the outside of the trigger spokes.

 

Thanks for the reply. 5158A. I thought it should be tight, but wasn't sure. I'll probably replace the distributor. It currently has a single vacuum advance(may not be original), I'm thinking about replacing with a dual vacuum advance to increase RPM's at idle to help cooling in the summer, any thoughts?

 

Sorry, 5851a.

 

If you are still using the original ignition box it cold be the problem.

 

Thanks, Beartracks. I changed it out before I found the bad terminal. I've used those boxes on International Scouts I've had in the past, so I carry an extra with me.

 

They can actually seem quite sloppy if you have not played around with them before. They should be smooth and consistent, without chunkiness or sticking. But they can flop around slightly, in addition to the smooth rotation that would be considered normal.
As you rotate the rotor and it's attaching post in one direction you will feel spring pressure as well. When you release it, the rotor should return to it's zero position.

Do some more checking while you're at it, I would say.
It's not out of the norm to need a new distributor after all these years, but the new stuff is hit-or-miss when it comes to quality. So be careful when just replacing parts these days.
Being yours is a '77 and it sounds like a standard Dura Spark style distributor (electronic) it's easy to at least test the inside module (magnetic pickup, or stator) with an ohm-meter. The two colored wires (purple and orange roughly) should measure 400-800 ohms between them. If they test outside of that range, or even close to the limits, you can replace the stator/reluctor assembly by itself, or replace the whole distributor, which should come with all the new stuff in it.

Got pictures of the distributor? Maybe it's original, as some did have a single advance mechanism still, while others had dual ports for an advance/retard setup.
But do not replace it just thinking it will increase rpms. It's not the job of the distributor to do that, it's up to the rest of the components of the vacuum advance system on these trucks.
In the late seventies it was quite the spaghetti factory under the hood, with some of the vacuum tubes routed through temperature controlled valves, timed delay valves, reducer valves, and all sorts of other stuff. If all you have is a stripped down setup (so many people removed and tossed "all that smog crap" that it's rare to find one intact anymore) with only one vacuum line from a carburetor port, then changing to a dual port vacuum advance will do nothing for your idle speed or cooling. Advance is advance, but the second (inner) vacuum port actually retards timing. Not good for cooling, but apparently handy for reducing emissions before computers came about to control all that stuff.

If you have all the support systems though, then by all means use whatever was supposed to be used for your year and model.

Paul

 

Thanks Paul, I'll check it out tomorrow.

 

I pulled and rebuilt the distributor. The pickup was very loose on the two studs that holds it in place and would move side to side and rock on the studs. No way to tighten them. The vacuum advance was shot also. No play in the shaft and the counter weights seemed fine. It was a pita getting the distributor to engage the oil pump drive, but finally got it back down.

it looks like someone had been in it before, no snap ring underneath the reluctor.

So far, so good. Thanks for the help.