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Corvette
C3 Forum
1970 C3 LS5 ... Question about fuel
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<blockquote data-quote="Rruuff Day" data-source="post: 226602" data-attributes="member: 2217"><p>This is from Bad Ass Cars site.</p><p></p><p><em>"This is a common problem that can be caused by a couple of things. Some people call this "dieseling" or "run-on". What is happening is; when you shut the ignition off, something, somehow is causing a couple of the cylinders to keep igniting, which in turn keeps the engine running, although "sputtering" pretty badly. This can be caused by excessive carbon build-up in the combustion chambers or on the piston tops which when hot it'll act like little glow plugs. This is common on engines that run way too rich or have oil burning problems.</em></p><p><em></em></p><p><em>Dieseling is a common problem with high compression / high performance engines, especially in warm weather or when the engine is hot. In this case, it's usually caused by running "cheap" gas with inadequate octane. In this case it can usually be remedied by switching to a higher octane fuel.</em></p><p><em></em></p><p><em>In milder street engines, another big cause for engine run-on is having the idle set too high, or the carb is mis-adjusted, which requires the idle speed screw to be screwed-in too far to get the engine to idle. When the idle screw is screwed-in too far, it opens the throttle plates too wide and the engine will actually pull some fuel through the main jets a little, so when you shut the engine off, the inertia of the spinning engine still pulls air (and some fuel) through the carb and into the cylinders. The heat built-up inside the combustion chambers is enough to light a few of the cylinders at random to keep the engine spinning and sputtering. Again, this is especially true with fuel that isn't high enough in octane. The more the octane, the less volatile the fuel. Even though the key is off, the engine won't stop sputtering because the throttle plates are opened up enough to still pass a little fuel and air. This is why even factory cars with carburetors (mostly 80's and early 90's cars) had idle stop solenoids to completely close the throttle plates off when the key is switched-off, which completely shuts the fuel and air off, thus preventing run-on from happening. With an idle stop solenoid, when you turn your key on it gets power and clicks into position which pushes the throttle linkage to the normal "idle" position, but when the key is switched-off, it allows the throttle plates to completely close-off again and won't allow any run-on. its a simple installation and Edelbrock makes one just for this application."</em></p></blockquote><p></p>
[QUOTE="Rruuff Day, post: 226602, member: 2217"] This is from Bad Ass Cars site. [I]"This is a common problem that can be caused by a couple of things. Some people call this "dieseling" or "run-on". What is happening is; when you shut the ignition off, something, somehow is causing a couple of the cylinders to keep igniting, which in turn keeps the engine running, although "sputtering" pretty badly. This can be caused by excessive carbon build-up in the combustion chambers or on the piston tops which when hot it'll act like little glow plugs. This is common on engines that run way too rich or have oil burning problems. Dieseling is a common problem with high compression / high performance engines, especially in warm weather or when the engine is hot. In this case, it's usually caused by running "cheap" gas with inadequate octane. In this case it can usually be remedied by switching to a higher octane fuel. In milder street engines, another big cause for engine run-on is having the idle set too high, or the carb is mis-adjusted, which requires the idle speed screw to be screwed-in too far to get the engine to idle. When the idle screw is screwed-in too far, it opens the throttle plates too wide and the engine will actually pull some fuel through the main jets a little, so when you shut the engine off, the inertia of the spinning engine still pulls air (and some fuel) through the carb and into the cylinders. The heat built-up inside the combustion chambers is enough to light a few of the cylinders at random to keep the engine spinning and sputtering. Again, this is especially true with fuel that isn't high enough in octane. The more the octane, the less volatile the fuel. Even though the key is off, the engine won't stop sputtering because the throttle plates are opened up enough to still pass a little fuel and air. This is why even factory cars with carburetors (mostly 80's and early 90's cars) had idle stop solenoids to completely close the throttle plates off when the key is switched-off, which completely shuts the fuel and air off, thus preventing run-on from happening. With an idle stop solenoid, when you turn your key on it gets power and clicks into position which pushes the throttle linkage to the normal "idle" position, but when the key is switched-off, it allows the throttle plates to completely close-off again and won't allow any run-on. its a simple installation and Edelbrock makes one just for this application."[/I] [/QUOTE]
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Corvette
C3 Forum
1970 C3 LS5 ... Question about fuel
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