Now that you guys helped me find the timing marks on my 1980 I-6 single barrel carter carbed beast, I got to work.

I got the little plate all cleaned up and was able to read it clearly with a strong flashlight. Every "tooth" was 2 degrees. I painted the tip of the 6 degree white so it is now clearly marked. (Decal under the hood says that it's supposed to be set at 6 degrees BTCD)

Decal under the hood says to disconnect the vac line to the distributor and plug it to check the timing. So, I pulled the vacuum line off the carb and the distributor and capped them with the little rubber vac-port covers, and got the truck warmed up to operating temp. Then, I hooked up the timing light.
At idle, it's advanced about 8 or 9 degrees. As I rev the engine, naturally, it advances more and more.

Recently, I've got new plugs, cap and rotor, wires, battery, etc. Put in a new h2o pump, thermostat, hoses, belts;
cleaned up the egr valve, and replaced all the vacuum lines and got rid of the stuff I didn't need. Replaced the ported vac switch on the h2o pump housing that runs the egr. Replaced carb and tuned properly, etc.
In short, it runs great, gets better gas mileage, and starts right up every time.

However, every now and then when I shut it off, it kinda diesels, but I think it's turning back in the reverse direction when it does it, because I've seen some fumes shoot OUT the top of the carb when it did it while tuning stuff up.

I'd hoped my timing was too retarded and that I cold advance it a little bit and that would make it stop doing this, but as I mentioned above, the timings already about 2-3 degrees advanced too far.

Please advise.

 

Sounds to me like the curb idle speed is just a tad high or if it has an electric throttle kicker it's not letting the throttle plate close when the key is turned off . That usually is the reason for the run on.

 

by electric throttle kicker, you mean a solenoid like the dashpot?
There's no dashpot. it IS an automatic choke, but the only electrical part is the heating element to turn it off.

curb idle is about 750 rpm.

 

I'm so glad you got the 80 running so good.
You've learned alot along the way.
I guess I would experiment at this point....set the timing at spec, put some upper end cleaner in (cleans the valves and combustion chamber). You may have some carbon buildup that causes detonation. Maybe tinkering with the idle speed.
You're close to perfection.

 

Yes a throttle kicker as I call it is a solenoid similar to a dash pot, except it operates opposite of a dashpot. The dashpot slows the return of the throttle to idle. The throttle kicker works as follows, it is a solenoid which pushes the throttle open.
The reason is to prevent dieseling or run on as some call it. Engines equipped with them are set up as follows: the engine idle is adjusted to spec required with it unplugged(deactivated) on the idle speed screw to that idle speed , then it is connected and the idle adjusted on the solenoid to the activated speed. What happens is on turning off the key deactivates it the throttle closes to the first setting which doesn't allow enough fuel intothe engine to cause the dieseling. I don't
have any info onthe 80 engine in front of me but 750 seems a little high.

 

srercrcr: thanks. You were a big help. I still plan a good writeup which I will post on here somewhere. What do you mean by "upper end cleaner?"
Is that like injector cleaner or is it an oil additive or something? Or do you mean pull the valve cover off and spray it down or something?

Kotzky: Could you describe what a throttle kicker looks like? Or maybe look at these pics and see if you can see one:

http://img.photobucket.com/albums/v1...-installed.jpg

http://img.photobucket.com/albums/v1...rog/truck1.jpg

http://photobucket.com/albums/v147/t...nt=vacuum1.jpg

NOTE: the third picture has a little mounted solenoid thing which I don't have connected right now. I'm not sure what it is. Perhaps that's what you mean?

 

your third photo shows a thotle solenoid designed to increase your idle speed usually used with a a/c back it off so that there is no way it can touch the linkage this might help

 

Look for "upper end" cleaners at the auto parts or a shop. It goes in the gas. It isn't fuel injector cleaner. It dissolves built up carbon on the back of valves and on the head. I would steer towards a quality (higher cost) brand. It may take a few attempts, that engine has been around for 25 years.

A shop I know has said some Ford engines are more prone to the problem.

 

That solenoid for the a/c shown in the third picture is completely removed right now and sitting on my dresser, so I'm pretty sure that's not the problem. Now I at least know what it's for. Thanks.

the carbon removal stuff... is that like the old "hotsoak" trick where they'd get the engine hot and dribble some cold water down the intake of the carb to break the carbon free?

I've also heard of removing a vacuum line and sticking it into a can of that "SEAFOAM" treatment. I think that's some kind of fuel additive or injector cleaner. They soak the whole can in slowly (while the engine chokes it down) and then turn it off and let it sit for a few hours and supposedly it eats away or loosens the carbon deposits and then they burn up and blow out the exhaust when you start it back up.

 

If you look at photo one and past the barbed fuel line fitting you can see the stem
of the solenoid. On photo three the item you have ID as #3 is your egr valve,
again looking at that side of the carburator under the fuel line the
cylinder with a wire coming out of it and the stem facing to the right
is the idle control solenoid or throttle kicker.

 

After reading a few of the posts concerning AC, may I suggest this,
check the wire feeding that solenoid. does it have current whenever
the key is on?? If so its purpose was as I discribed and I would
suggest that to make your engine work as it was designed you install
and adjust the part as it should be. If it is only energized with the AC
on I stand corrected.

 

I'll check and see if it's getting voltage all the time or just when a/c is turned on as you said.

If voltage all the time, i'll re-install, adjust, and get back with results of a hopefully non-dieseling motor.

 

One more question.

Could it be that the timing is advanced 2-3 degrees that makes it do this?
maybe if i retard it to factory specs it won't do it anymore???

 

To me it sounds either to advanced or lean at idle . I adjsut the timing until it runs the way i want it to sound and doesn't ping dow the road. Also on the carb adjust the idle mix screw (base of carb) but have a vaccum gauge hooked up to get the best reading.

BTW i wouldn't use a top end cleaner. Pull the head and do it right. The top end cleaner (ie Techron, Seafoam) will easily wash the oil off the cyl walls as it is cleaning your top end.

 

Well what did you find out. Voltage on all the time or just when the A/C is on?