I am driving a 1985 with a 351W 4X4 with a 4 speed manual transmission. I converted it to a dura spark II about a year and a half ago removing all the old "computer" junk. I have been running an Edelbrok 1406 for probably about 10 year with no problem at all. After the dura spark conversion the truck ran better than it has in a long time. No doubt it could use a tune up, plugs, rotor, dizzy cap, etc. Now to my problem.


About a week ago it hick-uped, sputtered, or coughed kinda like it had water in it, never actually back fired just kinda stuttered. I passed it off as a little water and kept going, no big deal. In the pass few day it stuttered a few more times again like water. Finally today things went south in a big way.


I drove about 30 miles with a few shutter but nothing very bad but it was very noticeable when it sputtered, again it seemed like water in the gas. I parked the truck for about an hour and a half and it started right up and I drove it about 25 miles. This time the stutter was very noticeable and cause a lose of power pulling hills. Again I parked for about 45 minutes and the truck started right up. I drove about 15 miles with quiet a bit of stuttering and power lose especially pulling hills, I am pulling a 16 foot trailer with a load on it. I parked for about 45 minutes to and hour. The truck started right up and only went about 5 or 6 miles, with major stuttering and power lose, before it died. It didn't immediately start up but after about 10 minutes it started and ran great for about 2 miles then back to major stuttering and power lose. I decided to park it and let it sit for a few minutes. It started right up and ran fine for a couple of miles then back to stuttering and major power lose. I had to stop 2 more time before I got home and each time I started back up the "good" running distance got less and less but I did make it home and parked it for the night.


I check the clear fuel filter and saw no water in it at all. I am thinking an electrical problem and more specifically the coil. I am thinking the coil is getting hot and breaking down but really I have no idea. I did pop the hood on one occasion when I shut it down and felt the coil and it was slightly warm but not hot. I would greatly appreciate any ideas/input from you gentlemen to head me in the right direction. I am not overly knowledgeable when it comes to electrically testing parts but I think I can follow instruction. Thank you for your help, guidance, input, and ideas.

 

Has it rained or been wet lately by you? Sounds like water under the cap.

 

Yes it has been raining for the last few days that's why I got out today, it wasn't raining and I had to go check my hog traps LOL. I never thought about water under the cap. I apologize for being ignorant but why would it start up and run fine for a couple of miles after sitting for about 10 minutes then go to running bad? It has never acted this way before but I will certainly check that first thing in the morning. Thank you for your input/ideas sir.

 

I think it is something that is getting hot and failing, and it is getting worse. In fact, it will probably leave you stranded sometime soon.

As for what it is, it could be the coil as you suggested. It could be the DS-II module. Or, it could be the pickup in the dizzy. In fact, it could even be the resistor in the wiring that supplies ~7 volts to the coil when when running.

So, how to find the culprit? That is going to be tough until it fails completely. Many of the auto parts stores have the ability to test the DS-II module, but unless it is in its failing mode it probably will pass, even if it is the culprit. But, one of the ways the modules fail is with the epoxy running out the bottom of them, so check for that.

 

Thank you sir, I will look at the module epoxy in the morning also. I didn't think of the pick-up in the dizzy either. Under these circumstances it will definitely be difficult to diagnose until it does actually break down all the way. On the upside at least I now know my emergency flasher doesn't work and I need a new flasher LOL. Thanks for the input guys I really do appreciate it.

 

We used to get computer circuit boards that were flakey to fail by heating them up with a hair dryer. Might try that on the DS module with the truck running and see if it starts cutting out.

 

I've. Noticed when mine gets damp it acts as you describe. I know my cap is cooked and when it does that a shot of WD under the cap gets it running again. Usually when he water starts to bake off is when it acts stupid. Cap rotor and wires are always a good thing anyway. I have only seen one pick up coil go bad in all my years and that was a gm product.

 

LOL Dang I never thought about that. I wonder if a heat gun on a low setting will work? I'm not sure how my wife would feel about doing that with her blow dryer LOL. I'm to old to need a blow dryer......not enough hair to dry LOL. Thank you I really appreciate your input it's a good idea that is definitely worth a try.

 

This will be the first thing I try in the morning. It's an easy simple fix if this is the problem. I think it is a good starting place and I'll go from there if it doesn't work. Again I really appreciate the input gentlemen.

 

I agree that damp weather causes all sorts of gremlins to appear on ignition systems which need maintenance. The moisture causes the insulating properties of air to be reduced, so it is much easier for a spark to jump from a bad plug wire to ground when it is damp. Or, to the wrong cylinder across the dizzy cap. But, those symptoms usually get better as the engine warms up since the heat dispels the moisture. So, I don't think that is what is going on here as the symptoms here get worse rather than better when the engine warms up. I think an electrical component is failing as it warms up.

 

Let the WD dry for a min or so. The carrier is flammable. Probably not good to seal it in a closed sparking cap. Lol

 

It could be. The gm pickup coil did run worse the hotter It got.

 

If it is the coil, the coil will be scorching hot when it fails.
Warm is normal.
Just touch it.

To me, it sounds like a failing DSII module.
I keep a spare under the seat and plug it in for diagnosis.
You don't even need to bolt it down, just drive and see if the problem is gone.

If not, and you can keep your hand on the coil for more than five seconds, test the pickup in the distributor by disconnecting the plug and putting an ohmmeter across the purple and orange leads.
You should have between 400 and 900 ohms in the windings of the pickup.

HTH

 

Thank you ArdWrknTrk I appreciate your input, I can certainly do this. Do I need to start the truck and let it run till it starts messing up then check the ohms or can/do I check it cold? The coil, not the pick up coil, apparently is fine because it never got any where near hot enough I couldn't put my hand on it as long as I wanted to.

 

Like any other component they tend to start by failing when hot.
There will be no harm done by testing while cold and seeing if you are within spec.
if it shows out of range, then you know right away.

Otherwise check it the next time it fails.

I find the modules tend to fail more often than the pickups.