86 Van 5.0L runon aka diesels

Howdy All Damn bugger will not stop! I shut the switch off and it just runs on and on. It scares the hell out of my wife. Almost made her late for work this morning, waiting for the Van to stop running. Running higher octane gas seems to help, but upsets my wife to spend an extra nickel a gal. I do not think that the carb. has an anti-dieseling solenoid.

Thinking about adding an in-line fuel cut-off.

Any ideas wellcome.

Reply to
iggy
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Carb is running lean and the pistons are getting hot enough to support combustion without spark when ignition is off, OR carbon buildup on piston tops is retaining heat to the point it supports combustion with no spark. Higher octane fuel reduces this effect as it has a higher point of ignition than does lower octane fuel.

Simply put, it's either running way lean, you have crud on your pistons, or both.

I'd start with some carb cleaner and top-end motor cleaner (water works just fine if you know what you're doing). Is this motor CCC equiped (i.e. has a computer and 02 sensor etc.)? If so, I'd scan for DTC's as the 02 sensor might be shot causing the lean condition as well.

Doc

Reply to
"Doc"

"\"Doc\"" wrote in news: snipped-for-privacy@adelphia.com:

Thanks Doc 86 Chevy Van. About 167K miles. Naturally aspirated. Rochester quad. If i can remember right, the only wires going to the carb are the choke heater and the A/C idle kick-up solenoid. Most likly both lean and carbonized. It is a PITA to adjust the carb. Easist from the front, through the very small 'hood', with a spring shaft driver. And then it is still a bitch getting the driver on the screw and keeping it there, with the engine warm and idleing. It has been a while since i looked last, but i think there is a thermal vacuum valve in the way. Know of any good 'dump in the gastank' decarbonizer. I might just wait till i pull the heads to replace the valve seals. Seems like they should wearout fairly soon.

BTW i bought it with 47K on it. Had to replace the batt and rebuild the carb then. It had been sitting for a few years. I put about 43K miles a year on it since.

iggy

Reply to
iggy

Does the AC work? I ask because if my memory is correct my mid eighties Caprice was set from the factory to turn the AC *ON* when you shut the engine off. My presumption was it was an anti-dieseling strategy as I can think of no other reason to do it. Of course it turned it off after a second or two as the AC is controlled by the ECM. If your AC isn't working then it won't add any load to the engine to stop the dieseling.

Reply to
Ashton Crusher

Down and dirty is shut it down in gear. As for "dump in the tank" try Berryman's Total Fuel System Cleaner, comes in a white metal can looks like a beer bottle, or Seafoam works really well too, but I have a hard time finding it where I am at.

Whitelightning

Reply to
Whitelightning

If you can get at the main bores through the doghouse with the air cleaner off, hold it at 2-3K RPM and slowly drizzle water down the bores. This will create steam in the cylinders and blow all the shit out. GM has a top-end cleaner that works pretty good as well, but water is cheap and has always worked for me.

Doc

Reply to
"Doc"

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