Charcoal injestion

[Pmac]

I posted this request for help recently but likely in the incorrect spot - it is not mouse droppings - the charcoal in all a uniform size and there is at least a cup(!)
"I found at least a cup of very small charcoal cylinder shaped (1/16th by 1/8th)pellets on top of my secondary air doors and in the bottom of the air cleaner two days ago. I put the pedal down on a country road and instead of the hearing the QJet moan – the engine was choking for air; I removed the lid and was shocked to find a cup (or more) of tiny black cylinders inside of the air filters , I swept them out as best I could and drove the ten miles home( no choice, rural area) the engine was barely running. I reckon something let go in the damned charcoal canister and when the air doors opened up it sucked the charcoal up the ‘clean air tube “ACLNR” ‘. The QJet is knackered, I know – but what about the engine? Has anyone seen this before? 1981 GMC C 1500 Canadian 305/350 camper spec. One more observation - the vacuum valve that closes the snorkel failed and although up to operating temperature the engine only had air coming in through the heat stove pipe ( and the clean air tube)."

[ron350]

Please post pictures so we can see.

[Pmac]

Ok, I will figure out how to attach images.
Added images to the original post but could not attach more to this message -

[geezer#99]

While closeups are nice, just zoom out and show us the rest of your air cleaner and how everything is hooked up.
Might help solve the mystery.

[Axle]

I've had that before, in my case the charcol got sucked into the carb via the pcv hose. If you got emmsiions inspections, take a ball bearing (or whatever you got handy that is a tight fit in the hose) and shove it in the hose at the pcv side that goes to the charcol can. Then you get to clean out the carb. Most of it can get blasted out with canned carb cleaner through the passages. And you will also need to pull the check ball at the bottom of the acclerator pump well and blast it out.

[Pmac]

Thanks for the reply - did you have such huge amounts of charcoal ingested?
I am concerned about what happened in the intake and combustion chambers - charcoal does burn, but what else is in that stuff from the factory, and after 40 years of use.

[geezer#99]

As was mentioned in your other thread, you can’t get anything into your carb thru the pcv connection on your carb. The passages of the vacuum port are under the primary throttle plates.
The only way it can get above the plates and into your air cleaner or into the float chamber is if you have a huge backfire.
Like I said. More pics help.
You can clean out the chambers by trickling a cup of water into the carb at a high idle. Basically you’ll steam clean the insides.

[kwmech]

Sure that is charcoal and not cast iron? I've seen cast iron manifolds do that. There is really no way you can get charcoal up into the filter area like that. The charcoal would be coming through a vacuum hose into the base of the carb. Hit it with a magnet and check under your heat shield

[Dead Parrot]

Pull off the carb and clean. Check for more stuff in the intake.
Check the hose(s) from the canister for loose stuff.
Pull the spark plugs and inspect for damage. While the plugs are out, pull the power wire off the distributor and crank the motor a few times. If there is some of the 'stuff' still in the cylinders, most should blow out via the plug holes. Then clean, gap and reinstall plugs.
Put carb back on, add the power to the distributor and see if it starts and runs.

[Axle]

Regardless of how or why, it gets there.
As for damage, none of any consequence. Happened at least 100k miles back on the engine.

[Pontiac1976]

If there a crack in the housing of the can or it was in a front end hit and seen and got broken with age more. Take out the Charcoal can ( down in the left fender 3 bolts- one as a clamp two for the bracket ) and check it. You might need a PVC valve. Oh there is a filter on the bottom of the can to that needs to be replaced ever so often.

[ron350]

I was hoping to see more pictures.

[Pmac]

“When you have eliminated the impossible, whatever remains, however improbable, must be the truth.” A.C.Doyle.
Condition: Stumble/stalls/will not restart/fuel overflowing from primary Qjet chamber and at least a cup of charcoal pellets from the canister sitting on the secondary air doors/valves of the Qjet on my ’81 C1500.
Cause: The air cleaner “THERMAC VALVE” temperature sensor did not bleed off vacuum – with the thermac air sensor stuck in constant hot Air Delivery Mode, no matter what the ambient air temp (about 75°F that day), vacuum was maintained to the snorkel motor/door(s) assembly , holding damper door up, shutting off outside air and allowing only hot air travelling up the tube attached to the heat stove (around the exhaust manifold) to enter the air cleaner through the tiny door built into the bottom of the snorkel – no fresh air source ; as the engine was up to normal operating temp, the choke fully open, and secondary throttle plates free to travel their full range of motion – the top air doors responded to the back barrels vacuum signal – as the defective THERMAC sensor’s vacuum signal held that snorkel valve shut tight (try assembling a factory air cleaner with out the top nut and watch what happens when the engine is revved to 1500 rpm, it will suck the top can down with some force – and that is just the draught on the primary side ).
When I went to W.O.T. that day (I have read posts in the past stating the snorkel valve would be pulled open by the carburetor’s fresh air demands but no so) the failed 40-year-old charcoal canister filter did not stop pellets from actuality traveling through the hose marked “ACLNR” on the canister to the “filtered air” hooded port in the air cleaner – ( that port is inboard of the air filter(s); this air cleaner still has the tall fine mesh ring that the “polywrap” once surrounded ) and charcoal was deposited into the primary chamber of the Qjet – resulting in a severe stumble, when I backed off the throttle, and the secondary air doors snapped shut, resulting cup or so of pellets dumping atop of the door plates, at least as much was ingested by the primary side.
Correction:
Removing the Air Cleaner I cycled the sensor several times with a heat gun checking each time with a infra-red thermometer – it did begin to function however but not within a practical range – (the Air Cleaner ‘can’ internal temp exceeded 140 F and the valve did not fully open) in my part of the world this system is an asset, as the outdoor temperature can be as high as 100°F and low as -40°F.
I removed the Qjet and cleaned out all the passages – and it functions! Remarkable how robust these Qjets are. I have not yet got the choke and secondary doors back to where they were pre-charcoal catastrophe – this carb used to start with one set of the choke no matter what how cold or hot it was, and the secondary air doors did open just as I wanted (it did take a week or more of set-up a few years ago to get there). The truck lives on.
So I hope this will help others – beware of the charcoal can and the THERMAC sensor.