'83 305 No more ESC, but now it is dieseling

[Johnny Atomic]

I was having intermittent trouble with my truck starting when warmed up, and diagnosed it as a bad ESC. I could bypass the ESC it would start, hook it back up would not start, bypass it again and it would start. I got another ESC module and now the truck will always start, but it runs badly, stumbling and choking when trying to accelerate. So lately I've been running it with the ESC bypassed using the little $19 bypass wiring plug from ebay. The truck runs great, but now it will occasionally diesel when I try to kill it. I've been killing it in gear to avoid this, then put it in park. In the last 2 years I've rebuilt the carb, replaced all the vacuum lines, and changed the plugs and wires. The truck is bone stock with all the 1983 emission stuff still in place and has 50k orig miles. I try to ALWAYS run ethanol free gas in it, it runs so much better on ethanol free. I have read that after bypassing the ESC you need to readjust timing. What timing should I use anyway? What was the stock timing set at?

 

[Vbb199]

Would seem like the module that's within your distributor is defunct, tho I dunno alot about the *older* ESC systems.

Just the 87-91

I would imagine if it's just mechanical advance... you could start at 8° btdc and see what it likes from there, tho someone else with a 305 may have input

 

[Vbb199]

If its an electronic type distributor (presumably it would be since it was using ESC), then 0° btdc?

Idk about those things pre TBI.

BUTTTTT
Your dieseling issue sounds like a potential distributor weight and spring issue maybe

Make sure they all move freely and aren't all crappy and getting hung up

 

[GXPWeasel]

I just went through the initial timing on my 305. It's freshly re-built, so that may make a little difference, but I set it at 12* advanced to start with, and I got really lucky because that's where it's actually running best at right now.

 

[SirRobyn0]

I was having intermittent trouble with my truck starting when warmed up, and diagnosed it as a bad ESC. I could bypass the ESC it would start, hook it back up would not start, bypass it again and it would start. I got another ESC module and now the truck will always start, but it runs badly, stumbling and choking when trying to accelerate. So lately I've been running it with the ESC bypassed using the little $19 bypass wiring plug from ebay. The truck runs great, but now it will occasionally diesel when I try to kill it. I've been killing it in gear to avoid this, then put it in park. In the last 2 years I've rebuilt the carb, replaced all the vacuum lines, and changed the plugs and wires. The truck is bone stock with all the 1983 emission stuff still in place and has 50k orig miles. I try to ALWAYS run ethanol free gas in it, it runs so much better on ethanol free. I have read that after bypassing the ESC you need to readjust timing. What timing should I use anyway? What was the stock timing set at?

IDK what to tell you some people seem to be happy with their 305's after bypassing the ESC others are not. Based on my experience (tried to bypass my ESC & now I'm in process of getting it to function correctly), I honestly can't see how anyone that values a good running truck could be happy after bypassing it. The 305's in the 80's when they were redesigned were built to have the ESC system and stuff like an EGR. For what it's worth I believe you will either have to live with issues, or get the ESC to function correctly. Most of the ESC parts are still available to order including the ESC module. It's something to consider anyway.

 

[R Carnella]

You didn't mention what octane you're using?
the first thing that comes
to mind is you need more.

 

[Vbb199]

I also did a little reading about the pre 87 ESC systems, upon deletion, its recommended to richen your mixture up a little, the carb plus esc is designed to operate on the leaner side of things for emissions purposes.

 

[JohnRod]

usually, 'diesel' or run on is caused by the throttle blades being too far open. meaning a higher curb idle speed. the engine continues to run because it continues to suck gas thru the carb. hot cyls. ignite the fresh fuel charge, and it continues!
rich jetting is also a culprit. as is over advanced timing. which makes the cyls. run hot.
pre ignition/detonation are also culprits in this situation. sometimes, way lean will make the cyls. run hot, and then with a fresh charge, the fuel ignites to 'diesel'.
having said that, I know nothing about your carb or TBI or how your timing is set.
the cure is to: turn timing back just a few degrees or slow down curb idle.
could be something as simple as the electric fast idle solenoid needing to be readjusted. or if a carb., some choke linkage needs tinkering with.
since you have changed things from the factory set-up, you will have to figure out, what the factory did, what you need to change. there are prolly 200K trucks like yours running around, so it can be done.
just hot rod it.
Rod in AZ

 

[Hottshot0069]

I sorry but what is the ESC? Where is it located? I am have a similar issue with dieseling, except my only does it when it has been running for a long time and when I change to a lower octane due to fuel pricing.

 

[SirRobyn0]

I sorry but what is the ESC? Where is it located? I am have a similar issue with dieseling, except my only does it when it has been running for a long time and when I change to a lower octane due to fuel pricing.

ESC = electronic spark control. This is over simplified but essentially the ESC system listens for pinging and retards the timing if it detects it.

If you're having an issue with dieseling start with basic checks. Check the base timing, idle speed, maybe the mixture. Check the carb for a idle kicker solenoid if it has one make sure it works.

Sometimes just dropping the idle speed a touch will solve dieseling.

 

[Johnny Atomic]

So I think may have resolved my desiesling issue. No dieseling currently after refilling with 93octane and pouring some Seafoam down the carb while keeping it running, then put the rest of the bottle in the gas tank.

I bought a timing light to check the timing, I cannot find a place to stand to see the factory timing marks. Does it even have a timing tab or marks on harmonic balancer? It is a bone stock low mileage 1983 305 w/ quadrajet. Did they not come with any timing marks when new???

 

[Johnny Atomic]

ESC = electronic spark control. This is over simplified but essentially the ESC system listens for pinging and retards the timing if it detects it.

If you're having an issue with dieseling start with basic checks. Check the base timing, idle speed, maybe the mixture. Check the carb for a idle kicker solenoid if it has one make sure it works.

Sometimes just dropping the idle speed a touch will solve dieseling.

"Kicker Solenoid", is that the same as the Idle Stop Solenoid?

 

[SirRobyn0]

"Kicker Solenoid", is that the same as the Idle Stop Solenoid?

Yes, it is I was using a more generic term. I'd say if it's acting ok now just let it be until you have burned though the tank. If you return to using 87 octane and the dieseling comes back then troubleshoot at that time.

 

[SirRobyn0]

So I think may have resolved my desiesling issue. No dieseling currently after refilling with 93octane and pouring some Seafoam down the carb while keeping it running, then put the rest of the bottle in the gas tank.

I bought a timing light to check the timing, I cannot find a place to stand to see the factory timing marks. Does it even have a timing tab or marks on harmonic balancer? It is a bone stock low mileage 1983 305 w/ quadrajet. Did they not come with any timing marks when new???

From the factory it had a mark on the ballancer and a scale on the timing cover. I have seen some aftermarket covers with no marks.

If you get up on the front of the motor like with you knees perched by the hood latch and look down between the water pump and the timing cover you should be able to see the harmonic balancer, and the tab on the timing cover with be right there at the top of the cover. Some SBC had the timing mark 90 degrees to the drivers side from there, and if that is the case it would be totally obscured on your truck, but it was only the older SBC that had those covers. Yours should be at the top of the timing cover.

After you have figured out where it is you should be able to lean over from the outside to see the marks when your timing it with the engine running. I just suggest getting up on it to see it for the first time with the engine turned off.

 

[greyghost]

timing to far retarded, idle stop solenoid not set to close butterflies completely when key turned off, adj by turning in n looking down into carb n set to butterflies fully closed, no fuel can be drwn into venturis, harmonic balancer possibly spun on rubber shock n no longer is mark accurate , either replace or use TDC tool to find no.1 cyl. and remark balancer with new mark, change your fuel source location no 7/11 gas try 66