Just got home from working on an older Ford tractor for a customer. From what I can tell from the serial number, and grill crest it's a 900 series from '55, but the 801 logo on the sides of the hood, the model of the Marvel carb, etc match up with the years given for the 801's built in '58. Either way the engine is a 172 CUIN so that shouldn't be an issue. The problem is this, when you shut the key switch off the engine starts to diesel and continues to run at a rough lope. It doesn't take much to stall it out and make it stop, but that's not the point.
The customer couldn't keep it running without alot of choke use. Since it seemed to be starving for gas I pulled the carb and checked it out. Sure enough there was trash built up in the bottom of the bowl as well as in the hole leading from the bottom of the bowl to the main needle. beyond that I found nothing wrong with the carb but a strange color inside the bowl. By steange color I mean it was Green. Has anyone else out there seen the inside of a carb turn green??? When I pulled the bowl the inside of the carb was a bright blueish green to a full green. It looked to me like the new crap in the gas might have been reacting with the brass parts in the carb and causing the color but I'm not sure. Like I said, I've never seen this in any of the countless carbs I've pulled over the years. Anybody got any ideas on the cause of the color?????
That said I made a new bowl gasket using the old one as a guide, rebuilt the carb, and got the thing running. From there I set the idle speed around 450 per the book, and the set the timing at 4 degrees, also per the manual. With these things done the old girl would run 'like a scaulded ape' and the customer was happy with the way it ran. The problem didn't occur until we went to shut it down after a few minutes of test riding. Again key switch off, definately no spark ( I checked), but the engine still wanted to run.
I know alot of the newer carbs, of all brands, used an anti diesel valve in the carb to provide a positive stop for the fuel flow through the main jet when the key was turned off but this one does not have that. So, basically it's key on, engine runs great, key off, and the engine continues to run and therefore suck fuel through the carb, for no apprarant reason, until you choke it down.
Anybody seen one diesel like this when shut down and any ideas wat could be causing it??? Any suggestions or experiences with similar problems will be greatly appreciated. Wayne
The customer couldn't keep it running without alot of choke use. Since it seemed to be starving for gas I pulled the carb and checked it out. Sure enough there was trash built up in the bottom of the bowl as well as in the hole leading from the bottom of the bowl to the main needle. beyond that I found nothing wrong with the carb but a strange color inside the bowl. By steange color I mean it was Green. Has anyone else out there seen the inside of a carb turn green??? When I pulled the bowl the inside of the carb was a bright blueish green to a full green. It looked to me like the new crap in the gas might have been reacting with the brass parts in the carb and causing the color but I'm not sure. Like I said, I've never seen this in any of the countless carbs I've pulled over the years. Anybody got any ideas on the cause of the color?????
That said I made a new bowl gasket using the old one as a guide, rebuilt the carb, and got the thing running. From there I set the idle speed around 450 per the book, and the set the timing at 4 degrees, also per the manual. With these things done the old girl would run 'like a scaulded ape' and the customer was happy with the way it ran. The problem didn't occur until we went to shut it down after a few minutes of test riding. Again key switch off, definately no spark ( I checked), but the engine still wanted to run.
I know alot of the newer carbs, of all brands, used an anti diesel valve in the carb to provide a positive stop for the fuel flow through the main jet when the key was turned off but this one does not have that. So, basically it's key on, engine runs great, key off, and the engine continues to run and therefore suck fuel through the carb, for no apprarant reason, until you choke it down.
Anybody seen one diesel like this when shut down and any ideas wat could be causing it??? Any suggestions or experiences with similar problems will be greatly appreciated. Wayne