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

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SirRobyn0

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Ok so here's the deal. My truck is a 1984 C20 with the 305. This is a carbureted 305 with the standalone ESC system. In order to not turn this into a novel, I'm going to cut to the chase. About a month ago the ESC system stopped working, or at least I think it has if my ESC test is valid. Result copious pinging.

I currently have new regular HEI distributor that I was thinking of stabbing in, but on my drive today I couldn't help but think about the benefits of the ESC and I'd like to at least gain a little knowledge on the system, and depending on cost of parts possibly take a crack at repairing it vs eliminating it.

#1. How to test function? Seems like running the engine and tapping on the passenger side exhaust manifold while watching the timing with a light I should see it retard the timing. Is this a valid test? If so then it's definitely not functioning.

#2. Seems to me from watching the timing with a light that the ESC distributor provides more vacuum advance and possibly more mechanical advance, than a standard HEI distributor. Agree / disagree?

#3. Seems like a pretty simple system, knock sensor, tip in sensor, ESC control unit, distributor. So I guess flow of diagnostic would be throw a knock sensor at it, retest. If still not functioning check for power and ground at control unit replace if needed. That's pretty much all there is, correct?

Thanks for the help!
 

dusterdude

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Interested

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86 SCOTTSDALE

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I can tell you when the ESC begins to fail it randomly through's timing around in bothe directions causing power problems and knocking. Replaced mine twice in the 90's , I'm not sure they even make them any more but I eventually got rid of it and never looked back when it caused the engine to not run at all.
 

Turbo4whl

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@SirRobyn0

Question #1: To test the system, warm engine, take a wrench and rapidly hit the passenger side exhaust manifold. This should mimic the knock sound, the sensor will trigger and retard the engine.

The RPM's will drop because the distributor will retard about 4 degrees. You will also see this with a timing light or meter. Make the test with the RPM above idle and keep rapping the exhaust manifold and it will drop another 4 degrees. (4+4=8)

Note: If you have headers you will need to hit the engine block or head with the wrench.

Question #3: On my '82 with ESC you can remove the system very easy, not sure if it changed in '85. The ESC system intercepts the wires to the distributor. Unplug the distributor connections, pull the harness up from behind the engine and disconnect the engine harness from the ESC harness and plug them into the distributor.

This is what failed on mine. The split loom broke away and the ESC wire harness layed on top of the transmission until it wore through and shorted to the trans case.
 

SirRobyn0

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@86 SCOTTSDALE I've already looked a little all the parts are still available, but must be special ordered.

@Turbo4whl Thanks for the info. Good to know my test method is valid. As far as I can tell all of the standalone ESC only systems were pretty much the same. I've read several methods to bypass the ESC, the one you described. Changing the module to a 4 pin, or changing the distributor. I think but do not know that the advance amounts in the ESC distributor is higher than that of the standard HEI distributor.

It would sure be nice to have a distributor machine right about now! But here is my observation. My truck currently has the timing set at TDC. If I plug the vacuum advance into manifold I get at least 20 degrees of advance. And the mechanical advance starts advancing at about 1,200RPM, which is pretty low. By about 1,800RPM I'm getting up over 30 degrees. Obviously my 40 year old advance springs could be weak. But anyhow without the ESC controlling all that advance I can't see how bypassing it would put me in any better position than having a non-functional system.

If I try to drive it with the advance can plugged in I get massive unsafe ping at part throttle. Under heavy throttle 3/4 to full I can get some mild pinging. I have not tried to check total timing as I'm not keen sitting on the top of the fan the revving the engine to 3K. That's where it would be nice to have a distributor machine. As a side note, yes my EGR valve is functional.

So I'm thinking of either replacing the knock sensor and see if that fixes it, or popping in the regulator HEI distributor and seeing if I'm happy with it then.
 

Turbo4whl

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Just to be clear, I did not have to change the module on the distributor, the engine harness had the same plug as the intercepting ESC harness.
 

SirRobyn0

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I can tell you when the ESC begins to fail it randomly through's timing around in bothe directions causing power problems and knocking. Replaced mine twice in the 90's , I'm not sure they even make them any more but I eventually got rid of it and never looked back when it caused the engine to not run at all.
How did you feel about the results of removing the esc on your truck. I've heard a lot of different opinions, from it ran so much better, to I had to retard my timing so much it's a dog now. So after eliminate the esc how did it run? Thanks
 

86 SCOTTSDALE

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How did you feel about the results of removing the esc on your truck. I've heard a lot of different opinions, from it ran so much better, to I had to retard my timing so much it's a dog now. So after eliminate the esc how did it run? Thanks
It ran fine with it but after replacing it twice and a few years later it developed an intermittent connection issue so I installed an MSC distributor and it has run great for the last 12 years so I would say I was glad to get rid of it.
 

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I removed my ESC on my 85 305, c10. When I timed it where it made decent power it pinged bad, when I timed it where I had no ping it suffered badly in the power department. When I swapped my ESC distributor weights, advance can, springs etc. Into the non ESC distributor I could live with it but still not 100 percent happy.I personally have 1 more trick up my sleeve if that does not work I am going back to ESC. A D1941 five pin module, the 5th pin retarded timing when it is grounded. I bought one I have yet to install it because I've been busy and haven't quite decided how I'm going to ground the pin. A hobbs switch possibly so at certain vacuum levels my distributor retards, a throttle switch so at certain throttle conditions the distributor retards or just a toggle so I can retard the timing at will. Anyway do not confuse the D1941 with the 5 pin module in Chevy trucks although they are both 5 pins they don't work the same. Had I known what I now know I would not have swapped distributors to begin with, ESC is easy to bypass without a distributor swap and you keep most of your original distributor functionality.Also have you checked that the EGR functions?Plugged EGR ports will cause ping also.
 
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SirRobyn0

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I removed my ESC on my 85 305, c10. When I timed it where it made decent power it pinged bad, when I timed it where I had no ping it suffered badly in the power department. When I swapped my ESC distributor weights, advance can, springs etc. Into the non ESC distributor I could live with it but still not 100 percent happy.I personally have 1 more trick up my sleeve if that does not work I am going back to ESC. A D1941 five pin module, the 5th pin retarded timing when it is grounded. I bought one I have yet to install it because I've been busy and haven't quite decided how I'm going to ground the pin. A jobs switch possibly so at certain vacuum levels my distributor retards, a throttle switch so art certain throttle conditions the distributor retards or just a toggle so I can retard the timing at will. Anyway do not confuse the D1941 with the 5 pin module in Chevy trucks although they are both 5 pins they don't work the same. Had I known what I now know I would not have swapped distributors to begin with, ESC is easy to bypass without a distributor swap and you keep most of your original distributor functionality.Also have you checked that the EGR functions?Plugged EGR ports will cause ping also.

See guys this thread points to exactly what concerns me about going away from ESC. One guy says going to standard HEI was fine the other says describes the problems Ricko does. I realize a dist swap on these trucks isn't hard, but still I don't want to be in Ricko's shoes. I think tomorrow at work I'll see how far away a knock sensor, and control unit are and give fixing the ESC a shot before dumping it.

Thanks,
I'll let you all know how it goes and what I do.
 

newguy11

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Any updates on this one?
I’m chasing a persistent ping in my 1985 high Sierra 305.

I did the hammer test and the knock sensor works. I couldn’t find any specific info on the tip in switch.
Seems that it is a vacuum controlled momentary contact switch that temporarily closes when vacuum is lost. I put an ohm meter in it and sucked in the hose. When the vacuum was released the resistance changed from “ol” to 13 then 26 in less than 1 second.

Don’t know if that normal or not
 
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SirRobyn0

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Any updates on this one?
I’m chasing a persistent ping in my 1985 high Sierra 305.

I did the hammer test and the knock sensor works. I couldn’t find any specific info on the tip in switch.
Seems that it is a vacuum controlled momentary contact switch that temporarily closes when vacuum is lost. I put an ohm meter in it and sucked in the hose. When the vacuum was released the resistance changed from “ol” to 13 then 26 in less than 1 second.

Don’t know if that normal or not
No I have not addresses my issues in any way. Currently running with vac advance disconnected so it doesn't ping. I really should get back to this....
 

Ricko1966

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Have you checked your base timing.If its too high the esc cannot pull enough timing to correct this. Also there's more to ping than just timing, heat, mixture, carbon. Put a timing light on it watch your balancer as you you connect and disconnect the tip in switch, is there movement?Watch as you tap the block by the knock sensor, movement? Verify ESC is the problem so you arent just masking the real problem.
 

SirRobyn0

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@newguy11 Ricko gives good advice on this, but from what you said it passes a hammer test would make me think your ESC is working. Check base timing if you haven't already. Check your EGR valve too. 305's need to have a working EGR valve or they will ping.
It's not uncommon for the intake passages to plug up as well.
 
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