Hi all,
Ive got a 66 122 wagon with a b20, and it sometimes starts running backwards when I turn the key off. sometimes it shuts off like it should, sometimes it sputters and shakes a bit and then stops, and other times, (more concerning) it kicks over and runs backwards, pretty fast for about 2 seconds and then stops. Ive been looking over other posts and around the internet in general but I'm not definitively sure of what to do... Does anyone have experience using Seafoam in these engines to get rid of carbon buildup, or is that a recipe for loosening up stuff I dont want to loosen up? Any other hints?
Im running 91 octane, (ive heard this is what one should do?) and it has a weber 32/36 now though it had a weber 38/38 and before that, SU HIF6's and it behaved the same way with these other carbs too...

Thanks,n

As usual, excuses in advance for my spanglish (english words in a "castellano" writing style):

Try accelerating when you switch off (worked with my P121 with one Stromberg ZS-175 carburettor some years ago, mine was a problem of brand of sparkplugs, then I moved from Autolite to Bosch).
--
Joaquin "Yogui' / Rojo 121 / Lima

Seafoam is expensive, water works just as well. Just use 1/2 cup of water, a 1/4" vacuum hose, get the engine nice and warm, connect the hose to manifold vacuum and insert the other end into the water for one (1) second sips. It helps to have the rpm at about 2000. That will get rid of most of the carbon in the cylinders and should help your dieseling problem.

Remember, the vacuum will drain a full cup real fast! That much water will fill a cylinder and break a connecting rod or wrist pin.

Klaus
--
My advice is free, so you got what you paid for...

Does your B20 have a vacuum retard unit on the distributor?--many B20's came with that system. It pulls advance back at idle and at cruising speed. The distrbutor rotates counter clockwise so the vacuum unit should pull in that direction too. See if you have that type and if it works--it should be connected to manifold vacuum. Every little bit helps.
One other point--maybe something you can't do anything about----various production models used variations of the Weber we know as the 32/36, etc. Some of them (Renault for one) had electric idle jets--shut the key--no more fuel--I used that system to great effect using two Renault/Weber 30/30's on a B20. The great number of vacuum ports on the production carbs also allowed me to tailor a simple water injection system (which kept the top end perfectly clean). -- Dave

HI, No It doesnt have a vacuum advance anymore. Ive just got the tap on the carb for it plugged...
Thanks,
n

Pretty common problem with these.
One thing that will help is to set the idle as slow as it will reliably stay running.
If it goes on very long you can always put it in 4th gear and dump the clutch.
--
George Downs Bartlesville, Oklahoma

Hello,

Does your DGV have a manual choke or electric choke?

The electric choke DGV should have an idle solenoid.

And IF the carburetor is properly adjusted, the idle solenoid will cut off the fuel supply to the idle circuit when the car is shut off, thus eliminating dieseling.

Also, if you are not sure whether you have an unleaded head, you should be using a lead substitute.

Water injection is not a bad idea.

Be careful, too much water can damage an engine.
--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502

Thanks,
The carb is a manual choke... another thing it does (just noticed it tonight driving home in the cold) if I floor it, it doesn't seem to have the get up and go I would expect, and it will backfire through the carb and loose power for a second. This kinda sounds like timing to me? Could the timing also affect the dieseling at all?
n

A momentary flat spot accompanied by a backfire is much more likely due to not enough fuel being supplied quickly enough by the accelerator pump (or clogged passageway). I took note of your answer to my post regarding the vacuum retard--that is--you wrote that the vacuum "advance" is disconnected. Is it advance?-- or retard? If a water treatment doesn't cure your dieseling it might do you well to have a working "retard timing" type distributor installed. If your distributor is actually a "vacuum advance" type then the vacuum should get hooked up. Another thought occurred to to me with your last post--is your mechanical advance working properly? Can you (with the motor off) twist the rotor further in the direction of rotation (counterclockwise) about 15-20 degrees and when released it snaps back to normal position?
BTW for general information---when I had my water injection hooked up--water (actually washer fluid) was supplied by an old (new part) Plymouth vacuum controlled heater valve (high vacuum--valve shut) hooked to manifold vacuum (I have a few of those - NOS valves if anyone wants to play with this type thing). Water got sucked into a ported vacuum spot--metered through a small carb jet (about a #85) inserted into the feed hose. It would use about a half gallon of water per tank (15 gallons) of gasoline and it completely eliminated pinging.
These days (10-15 percent ethanol gas) with the motor freshened up and despite a very high compression ratio it does not ping or diesel-- now with the SU carbs - and the water injection disconnected. -- Dave

Hello!
Thanks for all the tips. Im going to try giving it the water treatment and see if it helps. I have found that letting it idle for a while before turning off the key seems to help with the dieseling. My distributor has no vacuum anything. The mechanical part works okay like you describe, but there is no vacuum line to the carb, no vacuum diaphragm or anything attached to the distributor. Should it have one? would this solve my backfiring problem?
Thank you!
Nathan

I have this problem as well in a 67 automatic

If I turn the ignition off in park it will diesel like crazy but in drive it mostly shuts right off.

It sucks pretty badly but if I tune the carbs properly with the car in park it stalls when in gear.

To all concerned....tune your engines.
When my ignition and carbs are all nice and tuned up my engine does not diesel. My understanding of dieseling (run on) is that glowing embers in the combustion chambers continue igniting the fuel after the ignition is turned off. The glowing embers are the result of incomplete ignition of the fuel while the engine was in use, So tune it properly.
Over rich mix = incomplete ignition
lean mix = incomplete ignition
poor spark = incomplete ignition
poor timing = incomplete ignition
incorrect inlet/exhaust valves = incomplete ignition
Keep it simple.