Engine has trouble stopping after truck is turned off.
 

So a couple weeks ago, i drove my truck home and turned off the engine and the engine didn't stop right away. truck started to shake a bit like the engine was sputtering so i just dropped the clutch (it was already in gear) and killed it that way. I've checked it a couple times since then and i haven't seen the problem when the engine is cold, but after it warms up and i turn it off it does that. the truck has no issues starting or driving, just when I turn the engine off.

I'm not sure if its my imagination or not but it also sounds like its idling higher now as well. I thought it was just bad gas but I'm not longer sure that's the problem.

Could it just be that the Carb needs to be tuned since the weather has gotten hot the last couple of weeks?

I have an 300IL6 with a YF Carter carb i believe. has 1 screw on the corner facing the passenger headlight and 2 screws in the back that I'm assuming control the idle.

Any ideas on what the problem may be?

Sounds to me like you need to back the timing off. That is what we refer to as "dieseling". Otherwise you may be running too lean. Pull the spark plugs and check for signs of lean conditions.

Usual causes of dieseling:
Idle speed too high
Timing too advanced
Vacuum leak
Anti-diesel solenoid not working/mis-adjusted
Mixture too lean
It could be any one, or a combination of these.

Agreed with all of the above. Also note that an EGR motor in which the EGR valve ceases to function can exhibit all the symptoms of over-advanced and lean. It is pretty common for everyone's "friend who knows engines" to come over and put a BB in the vacuum line. My truck had the same setup when I got it and the PO's neighbor had stuck a piece of sheet metal between the spacer plate and the EGR valve.

STOP USING GAS WITH ETHANOL!

I can run about two tanks of 10% ethanol gasoline through my truck before the floats stick, it diesels, mileage drops like a stone, etc.

I've been running real gasoline in it and it's back to running perfect without doing anything else. These engines were never designed to run alcohol and it wreaks havoc on them.

Okay, I think I've narrowed it down to the fuel/air mixture and the idle being to high. For clarification, what does the cylinder look like if its too lean(after i pull a spark plug). i adjusted my idle speed and mixture until the engine ran a bit smoother and such but I have no experience adjusting a carb and the guides i can find online look vague to me. I know i need to go get a vacuum gauge and that's about as far as i get the picture. is there a guide anyone's posted for a 1bbl carter carb? I've gone through the forums and through youtube and google and its always generic guides or on lawnmowers.

After i adjusted the idle and mixture screws, the engine no longer "diesels" every time now but about 1 out of 4-5 times. so looks like its going in the right direction.

The rule of thumb (aka "generic") is to start by screwing the idle mixture screw all the way in until it lightly seats then back out 1½ turns. Start the truck and adjust in or out for best idle.
If you use a vacuum gauge, adjust for highest vacuum reading.

Not that it matters, but i messed up labeling the carb. its a YFA with elec choke. I'm going to head out and try and do that to the mixture and see what the results are! thanks for the help.

Ok i set the mixture back to 1.5 full rotations(screw spun 540 degrees) and then set my idle so that it was low but not stuttering at all even with sudden accelerations or deceleration. it sounded great while running and wasnt revving more than it needed to like it normally does, but when i turned it off same problem again. Was it 1.5 turns of the screwdriver or the screw? just to double check that.

My spark plugs are pretty new(30 days or so) and they still look new. no damage, doesn't look wet or anything. thats the only way i know to check for lean/rich conditions. i remember the old plugs didnt look damaged at all, they had bad gapping and were dirtier than hell but that was it.

Any Ideas now?

1.5 turns of the screw..

http://www.motorcycleforums.net/foru...gcondition.jpg

What is your timing set at?.. Verify this for us, and then we can help you troubleshoot this problem further.

How would i get the info for that its set at? sorry for the dumb question, i don't have a timing light or a vacuum gauge. If i need to get a gauge that can be arranged tomorrow. just trying to figure this out.

Time to buy a few tools .... or some beer for a buddy that owns them already!

You will need to use a timing light to set your timing properly. Ignition timing and fuel/air mixture are interrelated. I would start by making sure that the timing was correct, and then move on to fuel/air adjustments. Most common cause for dieseling (in my limited experience) is timing that is too advanced.

This link might help you understand a little better
http://grantorinosport.org/BubbaF250/perf/perf02b.html

Okay I had a talk with a friend who has a fairly good timing light and I'm going to head over to his house on Saturday. I had a couple questions about timing. I don't see any marks or anything on the harmonic balancer. Am I missing something? Does anyone have a picture of the timing marks? I watched a video from msd ignition and that helped explain stuff but I don't know about adjusting the curve, I just want it to run good haha.

They are often real faint, painted over, covered in grime. Save some time before you head over to your buddies and clean them up first. Some emery paper maybe. You can rub a white china marker over the grooves and wipe with solvent to make them more visible.

I assume the motor is a 300 I6 with the mention of the YFA carb .. Have a look here