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Old 10-17-2008, 10:06 AM
8689gwagons 8689gwagons is offline
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Join Date: Mar 18, 2002
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carb bowl vent question

88 GW Motorcraft 2100 carb. Front middle hose is vent, I think, goes to the cannister. What is the function of the in-line valve (which has a wire connection to something)? One of my jeeps has the wire connected, another does not. Thanks in advance.
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Old 10-17-2008, 11:59 AM
GWChris GWChris is offline
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The vent valve should be closed when the engine is running (key on actually), and open with the key off. More than likely the vent valve is bad, as the little rubber "hat" inside that forms the valve crumbles.

If the vent is open while the engine is running, this can affect your mixture. It is the difference in pressure between the area over the fuel bowl and the pressure drop in the venturi that make the fuel move. If the pressure over the bowl were to increase, then the mixture gets richer. The bowl should be vented to the inside of the aircleaner - venting it to the outside can mess it up.

If the valve is bad, then you're better off just blocking the vent at the carb. The only downside is that under really hot start conditions it may be hard to start due to build up of fuel vapors, but probably not a big deal.
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Old 10-17-2008, 02:35 PM
8689gwagons 8689gwagons is offline
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Thanks, Chris. That gives me some stuff to check out. The 86, which has the wire attached to power (and I assume the valve works,) starts at the turn of the key. The 89, which does not have the wire attached to anything, labors. I have re-done both vaccum schemes the same. Next stop after this vapor valve is carb re-build.
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