W111 Fuel Pump Diaphragm

[Bobsmyuncle]

Suffered my first breakdown of the Fintail. Luckily it happened overnight in my driveway! The fuel pump diaphragm is leaking. Looks like the pump is available but not the diaphragm. Anyone have any leads?

I read ages ago that a Fiat part was a good substitute. I sourced one, it isn't LOL.

However I'm in the middle of attempting a repair using the Fiat parts. If you are interested in the details or have some ideas or leads on a diaphragm you can check out the progress at my site. There are a few of us from the Fintail Facebook group in the same position.

Repairing a W111 Mercedes Fintail Fuel Pump

[Idle]

I am no expert on this pump, but I have rebuilt a lot of fuel pumps on US cars from the 60's.

The big failure part is the diaphragm. And from looking at photos of a Mercedes pump it looks like a diaphragm from a Porsche 356c would be a close fit.

Can you post photos of your diaphragm along with some measurements? The length of the shaft going through the diaphragm is critical so please post that as well.

Then hopefully some Porsche person will know the answer. Or perhaps you could post the question in the Porsche area?

[Bobsmyuncle]

Originally Posted by Idle

I am no expert on this pump, but I have rebuilt a lot of fuel pumps on US cars from the 60's.

The big failure part is the diaphragm. And from looking at photos of a Mercedes pump it looks like a diaphragm from a Porsche 356c would be a close fit.

Can you post photos of your diaphragm along with some measurements? The length of the shaft going through the diaphragm is critical so please post that as well.

Then hopefully some Porsche person will know the answer. Or perhaps you could post the question in the Porsche area?

I appreciate the input. If you check out my link you will see a bunch of really clear photos and measurements.

The 356 B/C 912 pump is quite similar (also a Pierburg) but from what I can see it see, different enough to prevent a swap.

www.type356a.com/APG.html

[Idle]

Originally Posted by Bobsmyuncle

I appreciate the input. If you check out my link you will see a bunch of really clear photos and measurements.

The 356 B/C 912 pump is quite similar (also a Pierburg) but from what I can see it see, different enough to prevent a swap.

Porsche 356 C / 912 fuel pump

That's too bad. Those rebuild kits are easily available.

In the old days of fifty or sixty years ago when we ran into a fuel pump that could not be replaced, usually due to the maker having gone out of business during the 30's, we would either buy a block out plate (or make one) and then install a low pressure electric pump. If you go the electric route make sure to insulate it well since the little ones put up such a whine and tend to vibrate the frame enough that you can feel it.

[Bobsmyuncle]

Thanks for the tip! I plane on having an electric installed as a backup.

[97 SL320]

When installing an electric, be sure to install a 2 terminal oil pressure switch that turns off when oil pressure is lost , ( Engine stalls but key is still on. ) This is to prevent the engine from filling with fuel if pump is on and engine off.

If you want to have a second level of protection, get an inertia cut off switch from a mid 80's and up to at least early 2000 Ford and mount it firmly to the car body. For what it looks like, search for AIRTEX/WELLS 1S3906 , this is the round red reset button type, there was also a rectangular white button type.

These rarely go bad so getting one ( get the plug and wire too ) from a self serve salvage yard is fine. They are mounted either in the trunk or right side front passenger kick panel.

[Bobsmyuncle]

Thanks! The oil pressure switch was planned, just looking now. That's a great idea about the inertia switch though thanks very much!

[Ziad]

I have the appropriate rebuild kits for that mechanical pump. Send me an email and i'll forward pictures.

It's a decent kit, not all of the parts may apply to the pump.

Each kit is $68 + shipping. I have sold many of these with no returns or complaints.

[Bobsmyuncle]

Originally Posted by Ziad

I have the appropriate rebuild kits for that mechanical pump. Send me an email and i'll forward pictures.

It's a decent kit, not all of the parts may apply to the pump.

Each kit is $68 + shipping. I have sold many of these with no returns or complaints.

Thanks so much for reaching out. I sent you a PM with my email address.

[Ziad]

W186300@GMAIL.COM

THEY'RE on Ebay now

https://m.ebay.com/itm/MERCEDES-W110-W111-AND-OTHER-MODELS-FUEL-PUMP-REPAIR-KIT-/302844720233

[CTD]

You can get the mechanical pump for about $40 on E-bay, new from Meyle.

[Bobsmyuncle]

Originally Posted by CTD

You can get the mechanical pump for about $40 on E-bay, new from Meyle.

Thanks, I saw the links you provided. I'm just deliberating whether it will work or not. Mercedes claims their replacement WILL work but that it attaches directly to the block and omits the OEM lever design.

[Idle]

Originally Posted by 97 SL320

When installing an electric, be sure to install a 2 terminal oil pressure switch that turns off when oil pressure is lost , ( Engine stalls but key is still on. ) This is to prevent the engine from filling with fuel if pump is on and engine off.

If you want to have a second level of protection, get an inertia cut off switch from a mid 80's and up to at least early 2000 Ford and mount it firmly to the car body. For what it looks like, search for AIRTEX/WELLS 1S3906 , this is the round red reset button type, there was also a rectangular white button type.

These rarely go bad so getting one ( get the plug and wire too ) from a self serve salvage yard is fine. They are mounted either in the trunk or right side front passenger kick panel.

A friend of mine installed an electric pump on his old Chevy pickup back in the late 60's. The original pump was NLA.

This was before civilization was advanced enough to run the circuit through the oil pressure switch.

Anyway, one day it would not start. So he kept cranking it, and trying different adjustments, etc. It finally fired and the cylinders were so full of gas that when they went off you could hear the boom a block away.

I know, because he lived a block away and I went outside to see what had blown up. I didn't see any fire or smoke, but I did see him working on his truck. So I went down there to offer my help but he said he had gotten it running, thanks away.

I asked him if he had heard the explosion. "Heard it," he said. "I caused it!"