diesels

[WVscottsdale]

now that I got my trans issues over with now I have a couple of new issues. it seems I get one done another pops up. the truck sometimes diesels when I shout it off and seems to be running rich. most likely the issues is hand in hand. I ran it this morning to town and it was fine and it was running rich, when I got back home I noticed that the manual choke was open but not fully open. so I started and ran it again and when I shut the truck off it started dieseling again. it has a 650 holley mechanical secondarys and manual choke.

 

[bigcountryguy19]

I was always told that it was timing issues that cause the dieseling effect when shutting down

 

[MrMarty51]

Mechanical choke needs adjusting on the cable.
After You get the choke so it finally opens fully, Your dieseling problem might be over, if not then, set the idle screw down so it idles at the factory spec. RPMs,

 

[HotRodPC]

Yep, all 3 of the above will do that. High Idle, Timing and Choke. Get those 3 under control, and problem will be solved.

 

[MrMarty51]

Thank You HRPC for confirming that.
I always take the " Timing " part of it out of the picture, as, when the ignition switch is turned off, the timing is also cut out of the scene, so, it can not be in timing if, there`s no power to the distributor.
Thaz all. LOL

 

[Driver4r]

A vehicle can also deisal if there is alot of carbon in the cylenders, cause it gets soo hot that it can actually ignite the air/fuel.

 

[WVscottsdale]

bad part with the choke is that it sticks and the cable wont push it all the way open its even hard by hand. I have the idle between 500 &600. i have a mild to big cam in it so it doesn't idle very well. I may put a spring on the choke to help it but not sure.

 

[HotRodPC]

Thank You HRPC for confirming that.
I always take the " Timing " part of it out of the picture, as, when the ignition switch is turned off, the timing is also cut out of the scene, so, it can not be in timing if, there`s no power to the distributor.
Thaz all. LOL

That is true, but at the same time keep in mind, with the ignition off it shouldn't be running either but it is. Many times, someone hasn't touched the idle screw, but they advanced the timing so far, and a bit to far, which also raised the idle. So maybe putting the timing right back where it was supposed to be, get's rid of detonation, AND engine run on, ALONG with lowering the idle speed, so you killed 2 birds with 1 stone. That is why I mention timiing in that situation.

 

[MrMarty51]

That is true, but at the same time keep in mind, with the ignition off it shouldn't be running either but it is. Many times, someone hasn't touched the idle screw, but they advanced the timing so far, and a bit to far, which also raised the idle. So maybe putting the timing right back where it was supposed to be, get's rid of detonation, AND engine run on, ALONG with lowering the idle speed, so you killed 2 birds with 1 stone. That is why I mention timiing in that situation.

AHHHHH SO, now I unnerstand.

 

[MrMarty51]

bad part with the choke is that it sticks and the cable wont push it all the way open its even hard by hand. I have the idle between 500 &600. i have a mild to big cam in it so it doesn't idle very well. I may put a spring on the choke to help it but not sure.

Fix the obvious first. get them kinks and tight bends out of that choke cable. If it is binding because of being embedded with dirt, then, replace it. I know all about them sticking choke cables. sometimes it takes a bit of lube in the shaft after the choke is pulled out, but, no matter the reason, get that cable so it works flawlessely.
If You have the idle set at 600 to 700 RPMz, then, I would be suspecting a bad vacuum leak, either in hoses, brake booster, intake manifold gaskets. If it burns some oil, with smoking out the pipes, but not real heavy smoke, then I would suspect the intake manifold gasket, or, of it is an automatic transmixer, then the vacuum servo may be damaged or wore out.

 

[Jims86]

timing only raises engine idle speed because its advanced, moot when shut down. over advanced timing will overheat the combustion chambers, and cause run on, because there is no way to shut off the air/fuel supply. Idle plates set to far open, or hanging choke, and Vac leaks are the biggest factors.

 

[WVscottsdale]

it also stalled out while pulling the mountain yesterday then as soon az I let off throttle ot regained itself

 

[WVscottsdale]

Yep, all 3 of the above will do that. High Idle, Timing and Choke. Get those 3 under control, and problem will be solved.

Gotta get my vacuum gauge and timing light and get to tuning. Lol

 

[MrMarty51]

it also stalled out while pulling the mountain yesterday then as soon az I let off throttle ot regained itself

Probably plugging up fuel filter.

 

[Boone83K10]

all the things mentioned probably all play a role in the dieseling.

While factory specs are a good starting point, most of us do not even have "factory" stuff left on our trucks.

1. fix the choke...then see if prob fixed.
2. fire it up and place your hands over the openings in the carb... if it continues to run, you have a vacuum leak that is allowing it to get air to continue to run...then check to see if prob fixed after finding leak.
3. get the timing right, between 8-12 degrees BTDC is good for most SBC...Make sure you cap off all open ports and plug the timing advance line. then check if prob fixed.
4. fire it up and let it warm, then shut it off. If fixed then celebrate. If not, you need to tune the carb.
5. Set the idle screw to give you around 700-750 idle in PARK. Start with initial vacuum reading. You said you have a healthy cam so do NOT expect a high reading, anything above 12 Hg is good for you. I see you're in WV, I am happy with the 14 Hg I get here in the high elevation of NC and unless you're higher than me, shoot for 12 Hg or more.
Tune each mixture screw, turning the same amount on both sides. Tune to highest vacuum possible. After that turn idle screw back down to 700-750 rpm in park. Check your vacuum again.
6. fire it up and check for problem. Celebrate if fixed.