fuel pump rebuild

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Steve Watson
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Re: fuel pump rebuild

#16 Post by Steve Watson »

Just an update. Used a 2mm longer bolt with the thick black gasket AND also installed a new pump cap (old one was definitely distorted where bolt head rests). For now, it's tight as a drum. No leaks at all. Something interesting that I noticed when I removed the cap with the new thick black gasket, AFTER it was exposed to fuel inside the pump. I noticed that the black gasket swells/grows after being exposed to gas. How did I notice this? Well I took a new black gasket out of another pump rebuild kit and compared it to the new one I installed in the pump cap and the diameter of the gasket was noticeably a bit larger than the fresh gasket. So...while the gasket is definitely too thick, the material it's made of appears to expand when exposed to gasoline and makes sense it would then provide a nice seal.

I still purchased a couple of MIL spec thinner cork gaskets from type356a.com, but for now my pump leak problems are resolved.
 

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Jim Clement
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Tag: 1957 356 A Coupe
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Re: fuel pump rebuild

#17 Post by Jim Clement »

here are some picks of a rebuilt fuel pump..
the main housing needed some machine work to accept the new valve.. then all worked well.
also shows the gaskets that were installed.
this is for an A car
Attachments
fuel pump 5.JPG
fuel pump 4.JPG
fuel pump 3.JPG
fuel pump 2.JPG
fuel pump 1.JPG
 

Kim Reeves
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Re: fuel pump rebuild

#18 Post by Kim Reeves »

ok - 5 years later on the post but i have a 356SC pump leaking a lot of fuel from the dome. Now this had a rebuild in 2018 - so maybe a 1000miles on this car since then - don't shame me! but we do have a primer pump at the front of the car that we use to fill the carbs up before we prime via the accelerator and then start the car when cold. Does anyone think the primer pump is hurting the main fuel pump - maybe putting too much pressure in there?
Shelter Island, NY
1964 356SC Coupe

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Martin Benade
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Re: fuel pump rebuild

#19 Post by Martin Benade »

No, but the dome either needs new gaskets, or has been over tightened at some point and bottoms out before squeezing the bottom gasket tightly. The dome is available separately.
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Kim Reeves
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Re: fuel pump rebuild

#20 Post by Kim Reeves »

Martin Benade wrote: Fri Jul 29, 2022 10:04 am No, but the dome either needs new gaskets, or has been over tightened at some point and bottoms out before squeezing the bottom gasket tightly. The dome is available separately.
thank you! going to do this weekend!
Shelter Island, NY
1964 356SC Coupe

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Martin Benade
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Re: fuel pump rebuild

#21 Post by Martin Benade »

A slightly deformed dome could be carefully straightened in a press, and might not crack. I straightened mine with some sockets in a vice, I don’t recommend that. I ended up with a couple of tiny radial cracks, so far the center gasket is sealing them.
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Graeme Langford
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Re: fuel pump rebuild

#22 Post by Graeme Langford »

I had to buy a new replacement dome as my dome was leaking and even a second hand replacement did not seal up properly
1958 356A
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Wes Bender
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Re: fuel pump rebuild

#23 Post by Wes Bender »

They're very much like the jet covers on Zeniths. They don't take kindly to over-tightening. As Martin says, if thy're not too distorted so that they crack when re-shaping them, you might get lucky. Only tighten down the retaining bolts on these items to the point that they just seal. Think a twist of the wrist rather than pulling on a wrench.
Some days it's just not worth chewing through the restraints.....

Kim Reeves
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Re: fuel pump rebuild

#24 Post by Kim Reeves »

OK - so could not wait and did the full rebuild last night following the video https://www.youtube.com/watch?v=AP0gpyDOVAQ and using the stoddard replacement kit.
Once assembled, primed the pump and fuel was coming out from the front cap and where the main valve gasket sits. The one thing i did was use the new springs, which i think i may just put back the old ones to not throw off the pressure, but in the video they machine the edges to create a new surface around the main valve gasket, is this necessary or can i do something else and do the screws need to be tight? I was able to tighten slightly the front dome and that stopped leaking but continued at the main joint. Also can i use the same gasket from last night, took forever for the kit to come in. Any advice would be great. Thank you so much!!!
Shelter Island, NY
1964 356SC Coupe

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Bruce Smith
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Re: fuel pump rebuild

#25 Post by Bruce Smith »

Kim-

All mating surfaces should be flattened prior to assembly. Not sure what you're calling the front cap or the main valve gasket. All valve seats need to be able to seal, and all screws tightened. A pic of your problem area may help.
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Michael Branning
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Re: fuel pump rebuild

#26 Post by Michael Branning »

Besides getting answers to direct questions here, another resource that's pretty new is the website document library search. Log in and access the Document Search under the Technical Menu. Direct link: https://porsche356registry.org/content. ... _id=579966

You can find detailed articles from the magazine.
Screen Shot 2022-07-30 at 9.49.45 AM.png
Click on the titles to pop up a description of each article, click on the green arrow to download the PDF.
Screen Shot 2022-07-30 at 9.54.53 AM.png
Michael Branning
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Kim Reeves
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Re: fuel pump rebuild

#27 Post by Kim Reeves »

Two more questions - i will rebuild - being that its only been 24hrs - is it ok to use the same rebuild kit? I see no damage since taking it off.
One more questions - the cap its self - there were some old gasket remnants which i scraped off - but could i use a flat sanding process on that as well.
Thank you so much for your support - the documentation is fantastic!
Shelter Island, NY
1964 356SC Coupe

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Martin Benade
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Re: fuel pump rebuild

#28 Post by Martin Benade »

I think what you are calling the main gasket is the pump diaphragm although it seals too. Did you put some pressure on the pushrod part while tightening the screws? You can flatten its mating surfaces on a piece of 220 grit sandpaper on a piece of glass or a iron table saw table. I think reusing the old springs is reasonable but the new ones are close enough not to cause leaks from fuel pressure.
Your new kit should be fine, and a bit of sanding could be done on the cover, but mostly get it clean.
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Jon Schmid
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Re: fuel pump rebuild

#29 Post by Jon Schmid »

Be very careful tightening the bolt that affixes the dome to the fuel pump body. The body material is made of butter, not guns. Don't ask me how I know... :x

Kim Reeves
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Re: fuel pump rebuild

#30 Post by Kim Reeves »

Thank you - so i sanded with some great 500/1000 paper on a flat surface and they have no light coming through, they make a cupping sound when put together - also did the same for the dome - was actually fun. Last question - the new gasket/valve piece - is it ok to use when it splits? this is not allowing me to upload a pic. the old one looks fine and does not split.
Also - the piece that attached to the engine block - is there a top and bottom - i never ID'd it. it looks interchangeable thank you again!!!
Attachments
IMG_9059.JPG
Shelter Island, NY
1964 356SC Coupe

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