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Mechanical fuel pump diaphragm
Posted by: radicalbuff ()
Date: March 19, 2021 02:47PM

Went to start our Corvair today, 1964 110, and the mechanical fuel pump is leaking in the spot where the rubbery diaphragm is. Does the whole thing need to be replaced or can it be repaired? I do not see any diaphragm replacement options in the Clarks catalogue. We did put an electric fuel pump up near the gas tank to use with a momentary (works just as many seconds as you push the button) button when it is too cold. Would that have anything to do with making the mechanical one leak? Helpful info would be appriciated. The rebuild was done in about 2016 by a very good Corvair mechanic (bless his soul) and I think the pump was new then. We have not put a lot of miles on it at all. Any ideas? Thank you in advance.

"Bucket List Project Manager!"
Deb ... Riverton, Utah



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Re: Mechanical fuel pump diaphragm
Posted by: joelsplace ()
Date: March 19, 2021 03:04PM

Often if the sit a few months they will leak when first started. Once the rubber gets some fuel on it the leak will go away until it sits again. The newest pump I have on a car leaked last time I ran it and then after sitting an hour or so it quit leaking.

Joel
Northlake, TX
5 Ultravans, 116 Corvairs and counting...

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Re: Mechanical fuel pump diaphragm
Posted by: SpyderMan ()
Date: March 19, 2021 03:09PM

I wold also double check that the screws are tight, they can come loose.

Sam Russell
Durham NC
1962 Monza Wagon Ted Brown EFI Gen II
1964 Spyder coupe


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Re: Mechanical fuel pump diaphragm
Posted by: jjohnsonjo ()
Date: March 19, 2021 03:45PM

I run my electric back up every few weeks over the winter to prevent that part from shrinking. Try that for a few days , plus tighten the screws.

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
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2016 KIA Sorento SXL Turbo

Bethlehem,Pa


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Re: Mechanical fuel pump diaphragm
Posted by: radicalbuff ()
Date: March 19, 2021 06:32PM

How tight for the screws? Is there danger of overtightness? I noticed a washer under one of the screw heads. I imagine there might have been a purpose for this.

"Bucket List Project Manager!"
Deb ... Riverton, Utah



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Re: Mechanical fuel pump diaphragm
Posted by: MattNall ()
Date: March 19, 2021 07:14PM

Going in a circle snug first then keep going until you can't move screw by hand

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Re: Mechanical fuel pump diaphragm
Posted by: Frank DuVal ()
Date: March 19, 2021 07:23PM

Yes, they will strip. AMHIK.winking smiley Then you get longer screws and nuts that fit....thumbs up It's just pot metal for the casting...

Frank DuVal

Fredericksburg, VA

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Re: Mechanical fuel pump diaphragm
Posted by: CorvairHaven ()
Date: March 22, 2021 06:37PM

Is there an obvious reason why replacement diaphragms haven't been marketed?
Or have they (recently)?

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Re: Mechanical fuel pump diaphragm
Posted by: joelsplace ()
Date: March 22, 2021 06:41PM

I'm too lazy to spend time searching but there is a thread on a company that made some kits a few years ago. They didn't cut the outer holes correctly and then never made any more. Do some searching, give them a call and see if you can talk them into producing more. I called them back when the thread was active and I don't remember what they said. If the kits were reasonable I would buy a dozen.

Joel
Northlake, TX
5 Ultravans, 116 Corvairs and counting...

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Re: Mechanical fuel pump diaphragm
Posted by: kenzen ()
Date: March 28, 2021 01:52PM

The diaphragms are mechanically attached to the push rod, which I think would be hard to perform without special tooling.

I don't think you can be "too tight" but you can strip the body threads very easily. I went and bought longer stainless screws and nylon insert lock nuts, which has made very tight seals possible, and solved my leaking pump problems. I don't remember the size.

kenzen
66 Monza Coupe 110/PG
Bel Air, MD

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Re: Mechanical fuel pump diaphragm
Posted by: joelsplace ()
Date: March 29, 2021 03:48PM

I'm guessing the kit came with the pushrod attached.

Joel
Northlake, TX
5 Ultravans, 116 Corvairs and counting...

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Re: Mechanical fuel pump diaphragm
Posted by: corventure Dave ()
Date: March 31, 2021 07:43AM

The kit's that were available "years" ago had a complete diaphragm and pushrod assembly. I believe these went away when materials made moved over "there".
When running an electric pump as primary, I do not trust the mechanical pump to not develop a leak. I made and installed a fuel pump blank, like Clark's and others sell that fits in the center of the mechanical pump and allows the stock fuel lines to be used.

Corventure Dave

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