Gas in vacuum advance


Old 09-21-08, 04:43 AM
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Join Date: Feb 2003
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Gas in vacuum advance

I have an 86 Toyota Corolla with 4ALC engine. The distributor has a dual diaphragm vacuum advance unit. I was servicing the distributor and found gasoline in the vacuum advance that is closest to the distributor. The other side was dry.

Does anyone have any idea how gasoline would find its way to the vacuum advance unit closest to the distributor?

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Old 09-21-08, 07:27 AM
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Obviously it not where you would normally find gasoline. There are some Corollas of that year out there with a carb, but most are FI setups. A lot of those Toyotas use the cold start fuel injector which is more of a central port jobby for starting, then the multiport for running.

The advance diaphragm for the distributor is drawn one way, then, relative to intake vacuum, relaxes and draws the vacuum toward the advance.

Just theorizing - I would suspect the vacuum, when reversed, picks up a droplet of gasoline from the throttle body, deposited there by the cold start injector and after a couple of cycles works its way into the diaphragm. The fuel may be channeled to the vacuum port by residues that have collected in the intake.
Old 09-22-08, 02:54 PM
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Mine is one of those that has a carburetor. After shaking the gasoline out of the vacuum advance, I applied vacuum with a hose to the fittings and sucked on it. I don't have a vacuum pump. Anyway, the diaphragm away from the distributor moved the arm easily. But the diaphragm closest to the distributor barely moved. This is also the side with the gasoline.

Not sure how these dual diaphragm vacuum advance works, but shouldn't vacuum applied to either side move the arm about the same? Maybe the the gasoline dried out one of the diaphragms?
Old 09-22-08, 08:00 PM
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no the vacuum doesn't move the arm the same. however if you had gasoline in the diaphragm it will soon go out it is not rated for that and will degrade the rubber.
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Old 09-23-08, 06:29 AM
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Strange things can happen when they use vacuum to control things
Had a friend with a Ranger, somehow used vacuum to control fuel pressure/pump. He was getting lousy mileage and it ran bad at lower speeds, dealer wanted $$$$ to just replace one part at a time. He finally found that some little diaphragm in a check valve (?) had failed and his brake booster was full of gas and it was being sucked int the intake.
Yeah, my details are fuzzy , but it was 10-12 yrs ago.

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