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Old 02-14-2007, 11:35 PM
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Default fuel shutoff solenoid

So my thermo teacher was saying that carbureted engines are bad because as the engine shuts off fuel still flows through the carb and washes down the cylinder walls, which introduces wear upon startup. But I just had an ephipone (I spelled it how I want to pronounce it) that Cruisers have a fuel shutoff solenoid. This would eliminate that problem right?
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Old 02-15-2007, 08:03 AM
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As far as I can tell, the fuel cutoff solenoid prevents the truck from dieseling. Fuel can't drain into the cylinders unless you have bigger problems or unless you still have enough vacuum to pull fuel through the venturi. The intake manifold is already soaked with fuel when you turn it off so maybe that washes the cylinder walls but I doubt our tractor engines really care.
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Old 02-15-2007, 03:13 PM
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Because the fuel is (theoretically) vaporized, as it's drawn out of the venturi, the moment you stop drawing air, you stop drawing fuel vapor. Sure, there could be SOME small amount of liquid fuel in the intake manifold, and theoretically, it might possibly run down into an open intake valve, but how much? What are the odds of an engine coming to rest in a position where the intake valves are open? I think your teacher is making a big deal out of a very low probability scenario.
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Old 02-15-2007, 07:26 PM
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He related an incident about a certain GM vehicle that had the engine tilted down at the rear to allow for a bench front seat. He said he's rebuilt engines in that particular vehicle where all you had to replace was the rear two or four cylinders, because the fuel left in the manifold upon shutdown fed into those rear cylinders by gravity, which washed down the cylinders and increased wear just on those cylinders. The front cylinders that were raised up still had oil on the sidewalls, so they didn't wear as much.
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Old 02-16-2007, 05:24 AM
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I'm with Bob on this. It sounds like more of a superstition to me. You can have an overly rich condition that has fuel washing down the cylinder walls and contaminating the oil but I thought that was due to carb malfunction rather than poor engineering.
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Old 02-16-2007, 08:12 AM
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Quote:
Originally Posted by subzali View Post
He related an incident about a certain GM vehicle that had the engine tilted down at the rear to allow for a bench front seat. He said he's rebuilt engines in that particular vehicle where all you had to replace was the rear two or four cylinders, because the fuel left in the manifold upon shutdown fed into those rear cylinders by gravity, which washed down the cylinders and increased wear just on those cylinders. The front cylinders that were raised up still had oil on the sidewalls, so they didn't wear as much.
Mystery solved.
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Old 02-16-2007, 08:22 AM
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Matt, it's an "epiphany".
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Old 02-16-2007, 09:40 AM
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I'm more into having ephipones (or ephipanys (ephipanies?)) and relevations.

Anyway he has never mentioned a Toyota engine in class, it's all Detroit (well he did mention the Honda CVCC the other day), but was maintaining that the carburetion and subsequent cylinder washing caused premature engine failure. I've come to understand that Detroit engines of the 50s, 60s, and 70s that were carbureted only lasted about 100-150 thousand miles, sounds like he's just making excuses knowing that those engines can't touch a F or 2F! Then when the B series diesels came out along with the 20-22R series, then the game was over.
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