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Fuel Pressure Damper Screw

Old 08-15-2018, 08:03 PM
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Fuel Pressure Damper Screw

Hey, Does anyone know what size the little screw on the fuel pressure damper is? My '91 3vze is having a hard time starting, and is smelling like gas in the engine bay, and I took a look at the fuel pressure damper today and the screw is missing. Hopefully that's my problem. But I don't know what size it was. Any help would be appreciated. Thanks.
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Old 08-15-2018, 09:56 PM
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No, that is not your problem, and replacing that screw will not help you at all.
https://www.yotatech.com/forums/f116...octite-266710/

The gas smell is likely due to a failed rubber diaphragm in the damper. You can test by jumpering FP to B+ with the engine cold (to slow the evaporation of any gasoline that leaks). Put a brown paper towel under the damper for a few seconds, and see if it is "wet" with gasoline when you pull it out.
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Old 08-16-2018, 07:09 AM
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Thanks for the response. I was looking at that post yesterday. Doesn't the screw put pressure on the rubber diaphragm and seal the damper? Saying it another way... if the screw isn't there holding that rubber piece wouldn't it leave an opening for gas to come out?
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Old 08-16-2018, 07:15 AM
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Sorry, forgot to respond to the other stuff you said. I have the intake manifold pulled off. Do I have to put everything back together to do this test? And can you explain "jumpering FP to B+ with the engine cold". What does this do?
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Old 08-16-2018, 08:48 AM
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Originally Posted by Labow View Post
.... Doesn't the screw put pressure on the rubber diaphragm and seal the damper? Saying it another way... if the screw isn't there holding that rubber piece wouldn't it leave an opening for gas to come out?
No. The screw doesn't go THROUGH the diaphragm. You can leave it out, and the damper works fine. Its only purpose is as a pressure indicator.

(Or, if you're asking something else, the diaphragm is crimped into the case all around its circumference. It's built sealed; it needs nothing else to make it fuel-tight.)

Jumpering FP to B+ bypasses the VAF-COR circuit. So with key-on, the pump will run (usually it requires key-start). (People have trouble with the VAF-COR a lot; jumpering is explained on this forum about once a week.) I suggested doing it cold to a) slightly reduce the chance of burning you up, and b) with a warm engine, the dripping gasoline will evaporate so quickly you might not even see it.

If you have the intake manifold off, all the fuel lines are off. I assume you mean the plenum (sometimes called the upper intake manifold). So where does the fuel go? In on the fuel line, into the right rail past the damper, over to the left rail, through the FPR, and OH! - out the disconnected fuel return line. Just put a piece of 6mm (1/4") fuel (or vacuum) line from the output of the FPR over to the fuel return line where you disconnected it on the right side. (Most vacuum line doesn't tolerate gasoline long term, but for the 10 minutes you'll be using it, it will be fine.)

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Old 08-17-2018, 10:51 AM
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Yeah, i meant the plenum. But I didn't take all of the hoses off, so a lot is still connected. I'll give this a go and see if its leaking. thanks for the info.
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