Help! Can't get truck to shut off!

[daniels84]

Hello, I desperately need some advice as to why my truck keeps dieseling. I have an 86 Sierra Classic 305 4bbl 700R4 with ESC. When I bought the truck it had a Carter carb on it. For one reason or another, I decided to change the fuel system back to Rochester. I located a parts truck that ran well and swapped back everything from it to make my truck stock and I used a buddy's truck as reference to make sure that I was putting the vacumn lines in the right place etc. The problem is that after I did this, the truck would deisel and refuse to shut off unless I disabled the ignition from the distributor. I thought that putting the carter setup back would cure this but, to no avail, it did the same thing. I've tried to retard timing, replaced all the vacumn lines with new ones, lowered the idle on both carbs, and swapped all the various emmision devices that run aff the carb but still the truck refuses to shut off on its own when the vehicle reaches it's normal operatiing temperature (it isn't overheating). The truck ran well before I messed with it and I had no problems with it running wise. I was wondering what could be the culprit- did I somehow stretch the timing chain, could it be someting inside the distributor, or is it something to do with the ESC? Any help would be greatly appreciated as I dearly miss driving my truck. Thanks

[Russell]

Hey man!

There are four things that I know of that can cause dieseling:

1) Too rich of a fuel mixture
2) Timing being off (too advanced or retarded)
3) Too high of an idle speed
4) High carbon buildup on the pistons that begin to glow after being exposed to the combustion for such a long time, the best way to fix this issue is to take the truck on a nice long 2 - 3 hour drive to burn all the carbon off.

Good luck with it man! My dieseling was caused by a combination of all four. I'm about 15 - 20 minutes East of you BTW

[cliffsta]

yeah mine will turn over an extra time real nasty if i don't wait long enough between turning the fan off, or even if i throw it in park and shut it off before it idles down. And its for those top 2 reasons; horridly bad timing chain, and an ancient carb.

[SanitysBane]

mine is from running to low of octane, AKA its detonating.

[cliffsta]

Originally Posted by SanitysBane

mine is from running to low of octane, AKA its detonating.

good point. I'm too broke to run anything but the nasty stuff, and my dad tells me how much better Ol Red runs on 89 or even 93 octane.

[SanitysBane]

well i usally run my truck on 93, but i thought that sence the 454 only has 8.6:1 it could handle 89, i was wrong.