ESC need someone that knows more about ESC system than I do

The yellow wire was broken when I opened it up to inspect it.
The plastic was barely hanging on by a thread at the coil connection underneath.
We only have 2 shops in town.
Everything else is 60-100 miles away, so a lot of times the repairs done locally are complete unit replacement. Engine, transmissions, DISTRIBUTORS...

It's fast, reliable and the ranchers get through faster at the shop.
I get the pick of the scrap bin
It's really clean, overall. Probably came off a cool old vehicle. Everybody drives a classic, where I live... Took a lil' Scotchbrite to the weights so you can see them clear...


The coil under weights needs replacing, unless you can solder the wires back on... and the shaft could use a good lube, while you got it apart.
Davis Unified ?
After my post count is up I'll list a bunch of cool stuff... many parts are new from my build...

I'm going to have to hunt for the module... It's in a small box somewhere...

Ok I've got a new ESC module here, and I've got a new ESC distributor. I've also got an standard GM HEI distributor that I'm not going to use, but it's the one I once tried. So I compared the to. So these new distributors they are kind enough NOT to mark the weights. But it's pretty clear the ESC weights look a little thinner so maybe a little lighter. The springs are a different color and much to my surprise the ESC springs, by feel as in moving the advance manually they seem a little lighter. Visually watching the reluctor ring on the pick up it looks like they move about the same amount. So IDK what that all adds up too, but it's clear the mechanical advances are calibrated differently.

So I'm hoping tonight after work to throw the module in and the new distributor and see what happens. HOPEFULLY this goes better than when I tried to put a standard HEI unit in.

Yep, the mechanical advance has several combinations of weights,springs and eccentrics,as well as vacuum advances. Which is why I get so weirded out about people swapping in a mystery distributor, junk yard,find,universal replacement etc. and thinking it's going to work right as/is and hook up and time just like their old one.That's why I told you to put your original back in and mod the ignition module. Gm is way better than us at figuring optimal curve for their engines. IMHO

Ricko1966 said:

Yep, the mechanical advance has several combinations of weights,springs and eccentrics,as well as vacuum advances. Which is why I get so weirded out about people swapping in a mystery distributor, junk yard,find,universal replacement etc. and thinking it's going to work right as/is and hook up and time just like their old one.That's why I told you to put your original back in and mod the ignition module. Gm is way better than us at figuring optimal curve for their engines. IMHO

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Right I get that I totally do and if keeping my old distributor was an option I would, you'll find out why in a moment why it's not practical at least not at the moment.

So anyone watching this thread here is the update. I installed the new distributor after work tonight and the new ESC module. It was kind of a rough day at work so I was 30 minutes past close when I started on it, took me about 30 more minutes to install the new distributor and ESC module, and time it. I actually timed it with the ESC module bypassed and observed the timing a bit. I timed it to 4BTDC spec is 6BTDC, but I have been running around on 2BTDC and an adjustable vac advance that I pulled way down I think it was limited to about 12 degree of advance. So I reasoned 4 would be a good starting point.

Also before hooking up the vacuum advance I revved the engine up, no more loosing 4 degrees before the mechanical kicks in, that's gone it behaves properly now. So whatever that was, was being caused by the distributor. Could I fix the old distributor possibly. At minimum I'd need to figure out what was causing that, and then I'd need the correct springs for the mechanical advance because one of them is clearly stretched and all of this is just from a quick look at it as I was pulling it out vs tearing it apart and looking it over. Maybe I'll do that later. For now I want to give this new unit a fair chance. It's listed for the ESC 305 trucks ONLY, so I feel like I have a shot at it being calibrated correctly.

So I hooked up the new ESC module fired it up and observed the timing at idle. For whatever reason before I knocked on the manifold I watched it take 4D out and then another 4D, and after a few seconds it came back. I thought that was weird but by then I needed to get going out to the farm, so I put my tools away shut the hood and started heading home. I made it to the highway, up on the highway and almost a mile when the truck sputtered and died. I dumped the contents of the glove box on the floor and sure enough the new ESC module was very hot. I plugged in my old unit and she fired back up, but pinged badly so as soon as I could I disconnected the vacuum advance line and plugged the hose with a pencil. That got me home, of course it ran retarded but got me home. Another ESC module will be at the shop by 9AM tomorrow.

So I will install another ESC module and see what happens. I have a bypass wire in the truck so even if it goes out on me in the future I will not be stuck somewhere because of it. If this next ESC module does not work correctly then I'll get one of the modules you suggested Rick and run that. Or go back to what I was doing with the adjustable vacuum can. Either way I've got to be in better shape not having the timing drifting 4 degrees on it's own.

New ESC module is here. After seeing the difference between the unit I received yesterday and the one I got today I believe I was mistakenly sent a core yesterday. Oh well mistakes happen, I wasn't left high a dry, but of course that was because of my own preparedness which is fine. I'll stick the new unit on at lunch and drive it around town, I've got errands to run anyway. Not much else to report at this time. Hoping for the best!

SirRobyn0 said:

Another ESC module will be at the shop by 9AM tomorrow.

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SirRobyn0 said:

New ESC module is here.

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I genuinely appreciate your appreciation for the factory systems on these trucks. It's fun to read about. Your efforts present many learning opportunities for anyone willing to follow along.

When my ESC distributor died (bad pick-up coil), I replaced it with a standard HEI distributor because it would have to come out to replace the pick up coil anyway. I later turned that distributor into my oil priming tool.

I may still have the functioning ignition module and some other parts from it. Let me know if you want me to look around the garage for any left overs. If you get desperate, I may be willing to pull the ESC module out from my K10 since I have no intentions of redoing that system. I have no idea of whether or not it's function though. Just wanted to throw that out there, especially for someone as helpful as yourself.

scrap--metal said:

I genuinely appreciate your appreciation for the factory systems on these trucks. It's fun to read about. Your efforts present many learning opportunities for anyone willing to follow along.

When my ESC distributor died (bad pick-up coil), I replaced it with a standard HEI distributor because it would have to come out to replace the pick up coil anyway. I later turned that distributor into my oil priming tool.

I may still have the functioning ignition module and some other parts from it. Let me know if you want me to look around the garage for any left overs. If you get desperate, I may be willing to pull the ESC module out from my K10 since I have no intentions of redoing that system. I have no idea of whether or not it's function though. Just wanted to throw that out there, especially for someone as helpful as yourself.

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Thanks I'm never sure if anyone is following along and learning as we go along. And if I learn and someone else learns something along the way then that's a good thing!

I don't think I need any parts at the moment, for a system that was not really used all that long parts are still fairly available which is nice.

When you think about the stand alone ESC system is actually a pretty sweet deal if a little rudimentary. And what I mean by that is even a slightly newer vehicle like a 90's rigs with a knock sensor has a base timing and the engine management computer can fluidly reduce the timing by 1degree up to 12 in most cases. But the ESC system can only take 8 degrees out and does it 4 degrees at a time. So it's a little more rudimentary yet it gets the job done. Maximum timing advance should always be present since the system should keep it just below the knock threshold. And who wouldn't want the benefits of that. So hopefully I'll have mine working shortly! We'll see what happens with the next module.

Put the new ESC module in at lunch and ran across town got propane and then ran around for about 20 minutes after that. Here is my assessment of a properly functioning ESC system.

It's awesome, but it's certainly not as refined as any modern spark control, or even 90's spark control systems.

So under certain conditions it'll very lightly ping very briefly, and then stop pinging. IDK, less than second I would think. I'll try to evaluate that a little better on the longer ride home tonight. It seems like a partial throttle depress from cruise is the most likely time for this to occur. And it's mild not anything that would be engine damaging. I think it's just that it takes the module a 1/2 second to detect the ping and pull back timing 4 degrees. I might consider backing down base timing 2 degrees if it proves to be a problem, but right now I'm thinking it won't be.

Overall I'm asking myself why I didn't do this sooner, the truck has more power and is more responsive than it ever has been. I'm really looking forward to cruising her home and seeing how she does.

Is your tip in switch working?

Ricko1966 said:

Is your tip in switch working?

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Good question, I thought about that as well, I will have to figure out how to test it and also how much vacuum change it needs to see to pull back timing.

I should also double check vacuum lines to the tip in.

I suppose the simple test would be to unplug the vacuum line to the tip in and see if the timing drops back momentarily.

Ok drive home report. It went good but there is some tuning to do still. First off I think how the system operates is pretty slick. Under certain conditions I'll hear just the slightest ping and then it's gone. That's obviously the ESC pulling timing. It would be cool to know how much as in did it pull 4 and then 4 more for total of 8 or just 4. Also under certain conditions such as travelling about 40 mph on a slight incline it will ping continuously but very lightly. If this was a car I might just let that fly, but given it's a truck and tow and haul with it not so much. I assume at that point it's pulled 8 degrees out and can't pull anymore. Keep in mind this is high mileage 305 or maybe I should say it's of unknown mileage. The EGR valve does function but it also uses some oil. So I think I'm going to install the adjustable vacuum advance can I had on the old distributor and take out maybe 2 or 4 degrees and see if that makes me a little happier. Lets also not forget I have the knock sensor on the wrong side of the motor, not really sure if that could make a difference or not.

But as a comparison at cruise with the old distributor and non-functional ESC the vacuum advance was set to limit of 12 degrees and I was running base timing of 2, for a total of 14. With the new distributor and functional ESC, the vacuum can is adding 18 degrees and I'm running the specified 6BTDC so that's a total of 24 take away the 8 total the ESC can pull out and that's 16, so it's no wonder I'm getting a little unwanted ping. I either need to knock back the base timing 2 degrees, or take 2 out of the vacuum can. I'd rather do the vacuum can so I'm not reducing base plus mechanical advance at higher RPMs.

Some of you might think I should try to figure out why it's still pinging with the 8 degrees pulled on a slight incline cruise situation, but in all likely hood that's a product of oil consumption and high mileage. Plus I need to run this truck 300 miles on Saturday so there isn't a lot time, and I don't think that the loss of a couple degrees of maximum vacuum advance is really that big of a deal. Especially when you consider where I was and where I'm at now. Certainly feels better in the gas pedal and I bet I see a fuel mileage increase as well.

I'm also trying to get the tranny pulled on my Jeep, so I probably won't have another report until afternoon or evening tomorrow.

There's more to think about here. Not all vacuum advances come in at the same vacuum. Meaning your other can may take more or less vacuum to start moving,maybe NBD maybe it will be. Something else to consider is what rpm does your distributor reach total with vacuum can disconnected. Now what rpm are you cruising at? You may be better off pulling base so you will have more advance at cruise so more mpg. Before I did anything I think I'd try better gas.

Ricko1966 said:

There's more to think about here. Not all vacuum advances come in at the same vacuum. Meaning your other can may take more or less vacuum to start moving,maybe NBD maybe it will be. Something else to consider is what rpm does your distributor reach total with vacuum can disconnected. Now what rpm are you cruising at? You may be better off pulling base so you will have more advance at cruise so more mpg. Before I did anything I think I'd try better gas.

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I agree with your thoughts on it's not a simple as. BUT I do not have a distributor machine anymore, and I hate perching above the fan and revving the krap out of the engine to try to see what the distributor is doing and when. So given those limitations some experimenting and trial and error will occur.

The mechanical advance starts pretty low and it did on the old distributor as well. I have not checked it with a tach, so other than to say low maybe 1,000 - 1,200rpm when it starts as a rough guess. I can also tell you that by feel, the springs in the new distributor are similar to the springs in the original, maybe a tiny bit stiffer, but given one of the ones in the old one looked stretched that's not a surprise. If I compare those two distributors to the standard HEI unit for a non-esc 350 I have at work, those springs are a bit stiffer. So I suppose I could try to swap those in to reduce overlap but (again without a distributor machine it's a guess), I think it would not do the trick. Reducing vacuum advance or base I think would be more effective.

Not going to run premium at least not yet. Well this is my thinking on that and why. If it's pulling 8 degrees it can't pull anymore and it's producing some unwanted pinging. So if I reduce timing 2 to 4 degrees whether that's done in base timing or vac set that aside for moment. So after the change, now it's not pinging on regular gas, but if I did decide to try premium the ESC would knock out less or maybe even no timing reduction and I might see a mileage / performance increase still and be able to run the fuel of my choice.

I really don't want to drop the base timing as that will lower total timing and I really don't want to do that. We are in a hilly area and when towing and hauling that little bit extra can make a difference, when pulling a hill at higher RPM in second gear. So I'm going to try the adjustable unit and see how it treats me. When I have the cap off the distributor I can always pull a vacuum on both cans and compare the vacuum at which each starts to move, that would at least give me an idea if there is a big difference there. I can always go back the standard can, or I can go back to the standard can and come up with a way to limit it, if need be.

Even though I'm kind of going against it I do appreciate your advise, to be honest with you I did not think of rate of the vacuum can until you mentioned it and will keep it in mind.

Oh, Rick I forgot to mention tip-in switch is working after cleaning up the electrical connections on the switch.