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Fuel in intake manifold


m.glisson003
04-22-2010, 06:03 PM
Is it normal to have fuel in the intake manifold? The fuel injectors inject fuel into the cylinders and they are at the end of the tubes of the intake manifold. Why would fuel be in the intake manifold itself? This is just be a stupid question but I just wanna double check and make sure thats normal. When I opened the valve I could see that it is very greasy in there and I could smell fuel.

RahX
04-22-2010, 07:12 PM
You get leftover fuel vapor in the intake. Over time it dries out and leaves behind a goo/gunk that is tan to black. Not to mention the oil vapor the PCV system deposits in there also. Year/make/model?

m.glisson003
04-22-2010, 07:30 PM
You get leftover fuel vapor in the intake. Over time it dries out and leaves behind a goo/gunk that is tan to black. Not to mention the oil vapor the PCV system deposits in there also. Year/make/model?

99 Pontiac Sunfire. I tried to clean it out as best as I could before putting it back on the head. It didnt look like there was any gunk in there.

serge_saati
04-22-2010, 08:16 PM
Not it's not normal. Maybe a problem with the PCV valve, not sure.

RahX
04-23-2010, 01:51 AM
A moderate amount is normal, if the intake sits lower than the ports in the head. It will puddle up a bit. Excessive amounts aren't good as it can suck into the cylinders and hydrolock the engine. Why did you have the intake off?

shorod
04-23-2010, 07:42 AM
Like RahX said above, I would agree that some film in the intake is not uncommon. Mostly what I've seen I would attribute to vapors from the PCV system doing its job, and I suspect if the vehicle sees a lot of in-town driving and not so much highway driving it may never burn itself clean. What I've experienced I would agree has a petroleum smell, I'm not sure sure I'd pin it as a fuel smell, although there is a hint of fuel odor to it.

Keep in mind that if it's truly just fuel vapors it would have evaporated in the time the intake manifold was removed from the engine and sitting on the garage floor/work bench. I would suspect the majority of what you are seeing/smelling is oil from the PCV system.

-Rod

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