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

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Ricko1966

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Okay well there are 2 types of adjustable vacuum advance cans. 1 adjusts spring tension inside the can with an Allen wrench to change the pressure to move the can,the other type has a screw that adjusts total movement of the can. Type 1 you need a limit plate. I'd try putting a piece of vacuum tubing on the stock vacuum advance can so you know its operating at the hg the factory intended.I'm not crazy the factory used to do that. The tubing made the pin fatter so it couldn't travel as far in the slot. I'll try to find you a pic. Found one Wow these are cooler than vacuum tubing.
 

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Ellie Niner

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Okay. It's funny how "this weekend or next" somehow turns into 8 months... but on my first visit back to the site in almost that long, this thread was at the top of Latest Posts...

My morked up ESC computer finally started screwing with the timing badly enough that we were going from engine trying to detonate itself into shrapnel to retarding the timing so far that the exhaust would glow. Having it dump timing on a short uphill onramp and taking about a minute with the accelerator mashed to the carpet to hit 80mph was the sh¡ts, so I picked up a used-but-good ESC computer on Fleabay... and we're back in business!

I saw a handful of different part numbers for different years and powertrain combos; the 16042121 looks like it covers 1983-86 305's with light duty emissions- save for California... which I think used the full CCC system with a feedback carburetor. TL;DR- it's kinduva pain in the ass making sure you've got the right part.

I haven't gotten all of the thermal vacuum switches and delay valves sorted, nor have I had a chance to even put a timing light on it yet, but the results are already positive enough (at least in my application and use case) that I will follow through and correct the rest of the stuff to make sure I've eked out as much as I can. I tried the cheap-n-dirty method of bypassing the ESC controller (not replacing distributor), but throttle response was soggy and fuel economy went down when I set the timing so it wouldn't detonate. Running premium helped, but it still wasn't quite right.
 

SirRobyn0

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Okay well there are 2 types of adjustable vacuum advance cans. 1 adjusts spring tension inside the can with an Allen wrench to change the pressure to move the can,the other type has a screw that adjusts total movement of the can. Type 1 you need a limit plate. I'd try putting a piece of vacuum tubing on the stock vacuum advance can so you know its operating at the hg the factory intended.I'm not crazy the factory used to do that. The tubing made the pin fatter so it couldn't travel as far in the slot. I'll try to find you a pic. Found one Wow these are cooler than vacuum tubing.
That vacuum tubing thing is a good idea I do like that. My adjustable is the allen wrench type. The only thing I don't like about using tubing or a ring on the advance can is it'll be kind of a crap shoot as to how much I take out, where as the adjustable one can be adjusted quickly from the outside. I'll look to see if a limiting kit is available locally. Thanks for that tip. But do want to ask what is the down fall to the allen wrench type, I assume it's that I'm adjusting spring pressure rather than the actual limit? Thanks.
Okay. It's funny how "this weekend or next" somehow turns into 8 months... but on my first visit back to the site in almost that long, this thread was at the top of Latest Posts...

My morked up ESC computer finally started screwing with the timing badly enough that we were going from engine trying to detonate itself into shrapnel to retarding the timing so far that the exhaust would glow. Having it dump timing on a short uphill onramp and taking about a minute with the accelerator mashed to the carpet to hit 80mph was the sh¡ts, so I picked up a used-but-good ESC computer on Fleabay... and we're back in business!

I saw a handful of different part numbers for different years and powertrain combos; the 16042121 looks like it covers 1983-86 305's with light duty emissions- save for California... which I think used the full CCC system with a feedback carburetor. TL;DR- it's kinduva pain in the ass making sure you've got the right part.

I haven't gotten all of the thermal vacuum switches and delay valves sorted, nor have I had a chance to even put a timing light on it yet, but the results are already positive enough (at least in my application and use case) that I will follow through and correct the rest of the stuff to make sure I've eked out as much as I can. I tried the cheap-n-dirty method of bypassing the ESC controller (not replacing distributor), but throttle response was soggy and fuel economy went down when I set the timing so it wouldn't detonate. Running premium helped, but it still wasn't quite right.
The 16042121 is the one my truck takes. BTW that crosses to an ESC100 Masterpro electronics which Orielly's can get. And that's where mine came from, remanufactured. My old unit was GM replacement dated 1998. I'll tell you the PO pulled all the vacuum lines on my truck so each and every thermal valve, check valve and delay are missing. I have my tip-in plugged directly to manifold vacuum as is my vacuum advance. Truly I'm not sure if the vacuum advance would be better off on ported, but it sure idles nice on manifold vacuum. Anything I tried to get around fixing the ESC resulted in what you said, soggy throttle response and poor fuel economy. I can't wait to have this last little bit of pinging taken care of!
 

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There's 2 types one limits travel one changes the vacuum level for when the can moves both are Allen wrench adjusted. My preference would be have the can move at the hg specified by gm then limit travel with a stop plate or bushing. I sent you a pic of bushings engineered for just this they come in different degrees
 

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Ok @Ricko1966 I have no idea off hand which style my adjustable can is. I will look up the specs and report back.

So I have a bit of an update and would like some feedback / opinions. I drove over to a doctors appointment and had some lag time before my appointment so I swapped in my adjustable vacuum can. Made a BIG difference, and Rick I may decide to go back to the factory one and limit it in the future right now I just need it better if that makes sense.

Anyhow on my drive back to the shop I made an observation. It does a good amount of what I would call very light pinging. Maybe this is normal for ESC 305? I've never driven a 305 with a properly working ESC system so I'm really not sure what to expect so maybe you and @Ellie Niner can give me an idea how normal that is. I don't want to tear up the engine, but I don't really think there is that danger, but would like some back up. It's a single exhaust truck so it's not loud and the pinging I'm getting now is just loud enough for me to tune in on it and hear it, but a passenger that's a non-car person probably would not. I might try to video it tonight, but I have a feeling the sound wouldn't come though very good.
 

Ricko1966

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Okay Robyn here's where I was going I putting up pics of 3 different vacuum advance cans. 1 adjustable and 2 different factory cans. I'm going to use the 2 factory cans as examples,and I'm going from memory I think the 1st can starts moving at 8-11hg all in at 18 next can starts at 3-5hg all in at 8hg . So if your truck is making 9hg at half throttle can 1 is barely adding any timing can 2 is still all in. I hope this makes sense to you the correct can will cam in and drop out to suit your needs. If you are getting ping at 1/2 throttle you may need a can that drops out sooner. They are both adding 8 degrees but starting and stopping at different vacuum readings. That's why I said I'd rather play with a factory can,because Chevrolet knows better than I do about when which engine needs how much timing added or dropped and at what rpm and vacuum readings.
 

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SirRobyn0

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At this point I doubt I'm going to do anything more to the ignition system before going to Yakima on Saturday it's actually another farm a bit south east of Yakima so it'll be near 350 miles by the time the day is though. I'll come home loaded with about a ton of feed and go over the pass both ways. But before that I've got some semi-local stuff to do Friday including dropping my Jeep tranny off at the builder, and hauling feed about a ton from him as well. And about 2 hours of driving tomorrow night so I'll get to test it a far bit, before hitting the pass.

So I left the shop a little early so I could take the long way, to the farm where I'd be in a bit of traffic go over a hill and then hit country roads. So I felt like it performed really well. One issue I had earlier in the day was if I was driving at low RPM, for example 45, in over drive and I'd just tip into the gas a little it would ping, pretty much continuously until I gave it a little more throttle, and this is extremely light throttle it was doing it at, it was a pretty light ping which isn't really bothersome on it's own, but I'm not keen on it going on and on under those conditions. So I switched the vacuum advance to ported and that issue stopped. I may switch back and forth a few times before I decide for sure which way I want to run it.

From looking at the factory diagram it looks to me like the vacuum advance ran manifold when cold and ported when warmed up, or possibly some other odd combination. There's a delay valve and the thermo switch on the manifold, which it is run though. So I'm thinking tip-in switch seems to be for larger vacuum drops, but tiny amounts off of no throttle or very little throttle seem to best handled by ported vacuum.

A LONG standing issue I've had this this truck is with it pinging bad like, Ellie niner said "detonate itself into shrapnel" bad at over 3,000RPM, with the secondaries open. So this hill I have to go over, is fairly steep according to google maps it's 1.5 miles long. I can go over it without getting into the secondaries, but if I nail it to the floor at the beginning of the hill I use make it easy 3/4 of the way up the hill before I'd have to let off the throttle and if I was running regular gas I'd let up sooner due to the pinging once over 3K in 2nd gear. So my experience with the ESC on this hill was AWESOME!!! I nailed it at the start of the hill, and two things we obvious when I got into the secondaries. The pinging was pretty much gone. What I mean by that is every few seconds I hear one ping, I'm not sure I've ever heard an engine make one solo ping sound but I think what it was is the ESC would pull 4 hold it pulled for a 1 or 2 seconds release it, detect that ping and pull it back out. I think that's pretty cool for a non computerized engine technology. The really striking thing was I had to let off the throttle 1/2 way up the hill as I'd picked up to much speed, that has definitely never happened before. I thought power was up, but now I know it's up.

Various other times at part throttle, (more than cruise less than 1/2) I would hear what I'd describe as barely audible ping that would last a second or two, I think that's was the ESC managing the ping as well.

At this point I'm just going to monitor it and see how it goes and how I feel about. I can still run premium when I tow if needed, either for ping reduction, or a bit of a power increase as the ESC won't have to back out as much timing.

I wish that it did not ping at all, but what little I get is very light and does not last long, like I said the bulk of it is barely audible, I doubt someone that is not a mechanic would pick up on it, and really I think that is the ESC functioning. It seems like where the newer systems can detect knock before we hear it at all, it's as if the ESC needs to hear it just a bit louder. I think it's just not as fast respond or refined as even the 90's engines that had knock sensors, and that's fine as long as that's really how it's suppose to be. I've never owned an carbureted 305 with standalone ESC system and if I drove one at the shop it was long enough ago that I don't recall it's behavior, my point is I have little to gauge it against except the early fuel injected rigs. For sure I'm happy about the power increase, which I hope means I'll pick up a little fuel economy.

@Ricko1966 Thank you for the part numbers, if I don't use them, someone else might. I think I'm going to run it as is, for now. If it proves to be problematic on any of my hauls this weekend I'll either back down the existing vacuum advance can, or reduce base timing, to get by on until next week when I can get into it again. Of course I'll be running it to the shop tomorrow as well, so we'll see how it does. I'll revisit the vacuum advance again if needed next week.
 

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@SirRobyn0 - Believe it or not, my 1986 Owner's Manual mentions that light spark knock under certain operating conditions is perfectly normal. IIRC, it even tries to spin it into a positive attribute... like the presence of a touch of detonation means that you're getting maximum performance and fuel economy or some such sh¡t :laughing1:

I'm not getting any spark knock at all right now, but I do remember faint pinging under the same conditions you're experiencing it, back when the truck was a lot newer than it is now (circa Y2k). I don't think I'd sweat it too much.

Last summer, I was getting really heavy detonation at high load/rpm... I haven't pulled our big car trailer since I replaced the ESC controller, but am pretty sure it'll do fine now.
 

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The part numbers and specs I put up were just as an example as to how the vacuum advance comes on and goes off. Those are old point fired cans but at the top of the list,all the descriptions were listed as to how much advance where it starts where it stops in hg. There are hundreds of different cans with different specs
 

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Sorry guys we had the salesman call in at the shop today. Normally the owner would come down to fill in but as luck would have it he's under the weather too. So I'm running double duty.

First thing I researched this a little last night but didn't get to post it, after this I'll respond to you guys.

Ok doing a little bit of reading on the vacuum system for the distributor. Basically it traps and holds vacuum to the advance when cold, using both ported and manifold as a source. Once warmed up some the thermo-valve turns off manifold vacuum, and the trapping system, thus leaving the distributor with ported only as the vacuum source. So with that said the best choice for me and closest to factory would be to just run ported all the time which makes sense based on my observations earlier.
 

SirRobyn0

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The part numbers and specs I put up were just as an example as to how the vacuum advance comes on and goes off. Those are old point fired cans but at the top of the list,all the descriptions were listed as to how much advance where it starts where it stops in hg. There are hundreds of different cans with different specs
I understand that but thanks for the clearification and thanks for the advice along the way.
 

SirRobyn0

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@SirRobyn0 - Believe it or not, my 1986 Owner's Manual mentions that light spark knock under certain operating conditions is perfectly normal. IIRC, it even tries to spin it into a positive attribute... like the presence of a touch of detonation means that you're getting maximum performance and fuel economy or some such sh¡t :laughing1:

I'm not getting any spark knock at all right now, but I do remember faint pinging under the same conditions you're experiencing it, back when the truck was a lot newer than it is now (circa Y2k). I don't think I'd sweat it too much.

Last summer, I was getting really heavy detonation at high load/rpm... I haven't pulled our big car trailer since I replaced the ESC controller, but am pretty sure it'll do fine now.
Really appreciate that info. and makes me feel a lot more secure about it. I know I have my owners manual but took it out of the truck and put it some place "safe" now not sure where that some place safe is....

So I took the long way into work this morning, and it behaved basically as it did last night. More power on that hill than before and other than one ting of ping every 4 or 5 seconds it was great, I think that's the ESC doing it's thing.

A bit of very light nearly inaudible ping, like I was mentioning yesterday, but really it seemed less than yesterday, I'm not sure why maybe I was over analyzing it yesterday, or maybe my direction of travel had me right at the cusp more often.
 

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So tonight will be the new test. Every Thursday after the shop closes I take a little trip up north to pick up food scraps from a food bank, that then becomes part of what we feed the chickens and other birds. This isn't a particularly long drive, 40 miles in total, and it's never a heavy load, but 10 or so miles of it is on the highway with a 65MPH speed limit. The is a fairly steep hill google says it's 2 miles long. In the past there were two ways to run this hill nearly wide open at the speed limit or in the right lane at 50 - 55 part throttle. So it will be interesting to see how it does tonight.

I'm really happy to see this coming together, my only regret is not having done it sooner.
 

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the mans on a mission beyond our comprehension but even if it wasnt for performance im sorta convinced he would do it for the science! of it. lol.
Well it's done. IDK if you have been following along the last few days, but other than possibly needing a little tweaking as I get some drive time in it's done. Relocated the knock sensor as we discussed about a year ago, got a connector and ESC module in, and a new distributor!
 

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Well that was a disaster, but better than being on the side of highway in eastern Washington. I wanted to do couple things on the truck in preparation for all the driving this weekend so at the end of the day at the shop I went to pull it in and it refused to start. This truck has always been super easy to start, so this was not like it at all. I went to check spark and of course it fired right up. So I pulled it in and did what I needed to do. Fired it up and drove away, made it a few blocks and it died, I coasted into a parking lot. I opened up the glove box and thought the ESC connector askew, so I pushed on it and it fired up. Seemed to run fine. So I put a zip tie around to hold it in place better. When I got to the next town over where I get on to the highway I noticed the exhaust seemed particularly strong, but I didn't get it quite yet. Getting on to the highway I would soon understand, the ESC module was not retarding. It was ping city, anything more than the lightest of throttle and I thought it might blow itself up. So I got off onto the shoulder of the highway and as I did so it stalled. Cranking it over it was that obvious sound of extreme timing advance. So I got out unplugged the ESC connector from the distributor and installed my bypass connector. Fired the truck and made it one exit up the highway where I got off to drop the base timing down. I'd stop several more times on my trip to change "tune" the base timing and change the vacuum advance amount. In the end I landed at 0 degrees for base timing. I added in 4 degrees back into the vacuum advance so that's still right on the edge of ping, I might pull 1 degree out, but had to back the base timing down to effectively and quick reduce the overall advance at higher RPM, and switched the vacuum advance back to manifold source.

That's about where I had the timing before but at least with this distributor the timing doesn't drop on it's own when you crack the throttle, and who knows what else the old one was doing at high RPM. So I feel like I'm a little bit ahead and even like this it's running better than before, but the power with hammer down is reduced a bit for sure.

So I'll be doing a 75 mile trip tomorrow and a 350 mile trip on Saturday without the ESC, and that's better than having to mess with it on one of the trips. So I'm ok with that I guess.

And I'm not giving up. I need to double check my wiring to make sure there isn't something shorting it out, which I doubt and then I need to either source a good module or get mine rebuilt, but one thing is for sure after 3 masterpro units I'm not interested in trying a 4th!
 

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