Should there be fuel in the power valve cover when removing it for inspection?

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twisted frame
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Should there be fuel in the power valve cover when removing it for inspection?

Post by twisted frame »

I am trying to diagnose a nagging bog while accelerating from, say, 40 MPH and stabbing the gas to accelerate.

I removed my Motorcraft 2100, and while keeping it upright, I removed the power valve cover from the bottom of the body. There was a small amount of gasoline in the power valve cover and the power valve itself was wet with fuel but not leaking any out. Is this normal or does this mean I should replace the power valve?

I would think it's normal to have a bit of fuel sitting in the power valve cover since I ran the engine only a few weeks ago but I wanted to check with the board, here. I replaced the power valve about 8 or 9 years ago when I rebuilt the 2100 but I don't remember if there was gas in the power valve cover when I removed it at that time.

I mainly suspect the accelerator pump diaphragm as one of the causes of the bog. When I checked that, the rubber diaphragm seemed to be kind of flimsy and not so firm like a new rubber one would be. I replaced it.
73 J4000. 360, MC 2100, T18A, D20, stock closed knuckle Dana 44 front, 60-2 rear. Warn Lock-O-Matics, Warn/Belleview electric winch, true duals with glasspacks, old-school front diff skid plate, used 265 Toyos on 16" AR wheels.
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tgreese
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Re: Should there be fuel in the power valve cover when removing it for inspection?

Post by tgreese »

No. There is a hole in the power valve diaphragm. Or its gasket leaks.

The TSM has a useful description of the power enrichment circuit (power valve). Vacuum holds the valve closed so when the diaphragm is punctured, enrichment is on all the time. The fuel added to the mixture goes through the valve into the main well, and is added to the fuel from the main circuits (coming from the jets). Normally fuel never passes through the power valve cover - only vacuum. There is a passage from the cover to vacuum, but it's blind and normally there can be no flow of fuel through the cover.

I've found that the accelerator pump (and maybe power valve?) diaphragm does not hold up well - maybe it's the fuel or parts quality.
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Topic author
twisted frame
Posts: 637
Joined: Wed Mar 27, 2013 9:41 am
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Re: Should there be fuel in the power valve cover when removing it for inspection?

Post by twisted frame »

Gotcha, thanks! Makes sense to me now. I replaced the power valve and accelerator pump diaphragm at the same time (years ago) so seems reasonable they would both deteriorate and go bad at the same time.
73 J4000. 360, MC 2100, T18A, D20, stock closed knuckle Dana 44 front, 60-2 rear. Warn Lock-O-Matics, Warn/Belleview electric winch, true duals with glasspacks, old-school front diff skid plate, used 265 Toyos on 16" AR wheels.
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nograin
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Re: Should there be fuel in the power valve cover when removing it for inspection?

Post by nograin »

I went through a couple of acceleration pump check valves on my 2150. Older materials + newer fuels = mystery results. If the umbrella style check valve is distorted - its fuel damaged and ruined.
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Topic author
twisted frame
Posts: 637
Joined: Wed Mar 27, 2013 9:41 am
Location: Massachusetts

Re: Should there be fuel in the power valve cover when removing it for inspection?

Post by twisted frame »

Good tip, thank you!
73 J4000. 360, MC 2100, T18A, D20, stock closed knuckle Dana 44 front, 60-2 rear. Warn Lock-O-Matics, Warn/Belleview electric winch, true duals with glasspacks, old-school front diff skid plate, used 265 Toyos on 16" AR wheels.
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