Took the 70 GS out yesterday and every time I shut it off, it ran on. I checked the initial and adjusted it from 12 to 10 degrees. The idle isn't too high. Idles at 800 in neutral. Im thinking its just the crappy gas we get these days at the pump combined with the extremely hot weather we've been having maybe? The engine is not getting hot. Frankly, its embarrassing when you go to a car gathering and your GS is running like a bag of excrement. Knocking 2 degrees off seemed to help, but its still there. I got it to the point where the engine shudders a bit on shut down. Still not right though. Im going to play with the mixture adjustment today to see if it makes any difference. Any ideas?
I wouldn't think adjusting the timing would change it any since it's not sparking with the key off. I'd check to make sure it's not dripping fuel from too much fuel in the bowl. Either leaky needle and seat or a sinking float. I've heard folks have had success pumping the brake pedal to make it stop. If you have power brakes..
I think its gotta be the combination of the hot weather and the ethanol in the fuel. Im going to try and get some 110 leaded and try that
Running on, as you well know Jason, is NOT GOOD!!!! Until you solve the problem what I would do is put the car in 1st. gear & let the clutch out a little to load the engine & slow the idle speed. THEN shut it off. For an auto just leave it in DRIVE. If the problem continues, & it may be because of the "Cat Pee" we have available to us as gasoline you may want to install an idle solenoid. Just some thoughts. Tom T.
In my experience, it is a combination of too much compression or timing and too low octane of fuel. Compression you cant change easily, you have brought the timing down some and it helped, so either bring timing down a little more or increase fuel octane if you can.
Jason, winter fuel in high temps makes it worse too. Still got some in the tank? As already mentioned, ignition timing is moot since ignition is off. The engine is essentially Dieseling. Fuel makeup, high compression ratio and excessive idle throttle angle are culprits. Devon
Good call Devon! I didn't think of that. And I sure do! I just filled the tank and diluted what was in there. I bet it will take a couple tank fulls to get rid if it all. I guess Im just going to drive it around. Gee....what a chore! :laugh:
Make sure if you have any vacuum ports plugged, that the dieseling didn't pop them off. When it diesels like that it's doing it in reverse of normal engine rotation. I've had that happen on mine and found a plug lying on the belhousing after a diesel "episode".
Yes, since while deiseling the engine is turning in reverse, air is being pumped up into the carb and out all its vacuum ports including the power brake port. Pumping the brake pedal uses the big diaphragm to now counteract those positive pressure pulses from the reverse turning engine.
Yep. That last galloping gasp is in reverse direction. Witnessed it with my own eyes, and had tha vacuum plug get blown off the carb.
Certainly, dieseling is ignition without spark. That requires a hot spot as an ignition source or VERY high compression. Retarding timing normally brings it under control but maybe for different reason than spark. Retarding will result in a lower idle rpm, even adjusting idle lower will sometimes resolve problem. An idle solenoid stop closes the throttle and reduces fueling usually will fix it also. Typically only one or two cylinders fire and keep it rolling (and knocking!). Have you checked plugs for blistering or signs of being the wrong heat range. Something in there is the ignition source, is it a chunk of carbon or is it the spark plug glowing? Not all engines diesel for the same reason and not any one solution for all of them. Engines have too many variables to say for sure what is causing yours but the one of the fixes already addressed by others will apply to yours. Ah, and yes I have seen the engine kick back just before going static dead, just haven't seen one run backward.
I've had a few engines that would "run-on" after the key is off. If in gear, it normally pulls down in a moment. Only on rare occasions did I see the REVERSE "run-on". It comes at the end of foreword run-on. You can know it by the white smoke cloud that blows out the air cleaner or rushes from under a closed hood. Also, the reverse "run-on is a much faster rpm than the forward run-on,... fast as the flutter of gargling mouthwash, and lasts only a fleeting moment as it pukes out a big fog of fuel vapor like a mythical dragon....then silence.
Run on is dieselling unless there is an ignition issue. Are you sure it is actually off when you turn it off. No recent "one wire" alternators or other changes. The factory harness has a diode to prevent power from the alternator from seeping back into the ignition circuit. You might want to try a test light at the coil or distributor to make sure the power is instantly off when you switch it off. Silly things can happen with a worn switch too. If the power is off instantly with the switch,you are probably going to have to idle it down even more. Dan
