EFI Fuel Pump O-Rings

[Captain Obvious]

I've got my 77 EFI fuel pump torn apart and when I put it back together, I want to use new O-rings to seal the rotor section. Anyone know the sizes that are used there?

Are they available as a replacement part? I looked through the parts docs and I couldn't find an exploded view of the fuel pump. I'm thinking they aren't available separate?

I measured the old ones that came off, but they're deformed from over thirty years of service. They are no longer round, nor are they circular in cross section. By this time, they are oval in cross section, and are shaped like the groove they came out of.

However... Doing the best I could, I get 33mm ID and a 2mm cross section?

I know others have been through this (EuroDat) but I never found closure on the O-ring size.

[EuroDat]

Hi Captain,

I changed the o-ring because the house o-ring was leaking and noted the sizes somewhere in all that paperwork I have been collecting over the years. Ill have a look when I get home.

Its been two years and no more leaks so the size I used must be close to original.

Chas

[Captain Obvious]

Thanks Chas. When you get a chance to dig through your notes, I'd appreciate any input you have. Mine wasn't leaking, but I took it apart because, well... because I do that. Actually, my input filter has disintegrated, and I wanted to make sure there weren't little bits caught up in the works.

One other thing. I'm sure it's nothing, but just to be sure... You keep talking about "O-ring" (singular) instead of "O-rings" (plural). You do know there are two of them, right? One on either side of the rotor housing?

Here's a pic of where I am now. You see the my original O-rings have taken a set which makes measurements less accurate:

[EuroDat]

One other thing. I'm sure it's nothing, but just to be sure... You keep talking about "O-ring" (singular) instead of "O-rings" (plural). You do know there are two of them, right? One on either side of the rotor housing?

I mean the two o-rings and if I remember correctly, they are the same size. I thought I may have taken photo's of the internals with the size written next to it, but I seem to have rebuilt it without taken any photo's of the internals:stupid:

You can never take enough photo's. Thats a lesson I have learnt the hard way.

Chas

[Captain Obvious]

Figured you knew there were two of them, but since keystrokes are free, I thought I would just double check. My measurements also show that the two of them are the same size.

I agree on the photos. Can't have too many.

In fact, that one pic you just posted above with the fuel pump mounted in place under the car answered a few other questions for me... My previous owner replaced all the hardlines (brake, fuel) going from the front to back of the car. And I've had suspicion that not all of the routing of what he did was the same way it came originally.

Your photo confirmed that. He used some poetic liscence in the routing. I don't think it's a big enough deal for me to take them out and start over, but at least now I have a pic of how they're supposed to route. Thanks again!

[Zed Head]

Way back when I remember seeing seeing general guidelines on sizing o-rings based on the gap they were sealing. They're supposed to compress a certain amount but not fill the gap. The circumference is not meant to stretch much at all, the point is to just gap-filling. The proper word for the purpose is "gland", I believe. So really, you should be measuring the metal parts, not the rubber, to size the ring. Found a few references but there's a ton more out there. You could spend some quality fun time just studying the possibilities.

eFunda: Introduction to O-Rings

Gland Dimensions

http://www.parker.com/literature/ORD%205700%20Parker_O-Ring_Handbook.pdf

[EuroDat]

Where I work we use hundreds if not thousands of o-rings in the processing equipment. The most common standard is AS568A and BS-1806, but its a big list.

Still site will give you and idea of the common standards, but it doesn't end there: O ring sizes including metric and International standard O-ring sizes.

I will look first thing tomorrow morning. If I cant find the info, I can calculate the o-ring size again, but then Ill need some more info. A quick How To in measuring odd shaped o-ring grooves.

Chas

[Mark Maras]

We have a large ACE Hardware store in Portland that stocks a large selection of O-rings in different thicknesses and diameters. If I remember correctly. they're in the plumbing section. You might find them there.

Mark in Portland

[Willoughby Z]

I assume the O-rings being discussed come in contact with fuel, so wouldn't any replacement items need to be rated for solvent/fuel?

[EuroDat]

I assume the O-rings being discussed come in contact with fuel, so wouldn't any replacement items need to be rated for solvent/fuel?

Yes, They will need to be NBR / Nitrile material. Most plumbing rubber is butyl (of course there are exceptions) and will work but have a shorter life expectancy.

Chas

[Mark Maras]

Eurodat is correct. Fortunately the Ace in Portland carrys O-rings in both material. Go with the nitrile. It's always a good idea to do it right. No worrys later.

Mark in Portland

[hr369]

I also have a need to find the proper size o-ring. This is what I came up with.

These bosch fuel pumps look very similar to the type 3 vw.

The electrical connector is a bit different but I think the

internals could be the same. This is a D-jet and we have

the later L-jet.

It's a msft doc file that a vw guy put together.

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=9&ved=0CG8QFjAI&url=http%3A%2F%2Fwww.vwtype3and4club.org.uk%2F_docs%2Ftype3and4%2FFIPumpoverhaul-2.doc&ei=0VAaU8rQH4LpoATgiIG4CQ&usg=AFQjCNHZIgNkC1K_nGE3Z1Awm6UUdIyQDg&sig2=PkPxoTxvicpAYyxmI9UYPw

Replacement O-ring Details

Metric sizes ---- Motor casing One - 48mm inside dia x .5mm

Pump head Two - 30mm inside dia x 2.0mm

PRValve One - 10mm inside dia x 2.0mm

Imperial sizes --- Motor casing One - 1.862” inside dia x 0.103” - BS No – 134

Pump head Two - 1.176” inside dia x 0.070” - BS No – 025

PRValve One - 0.364”inside dia x 0.070” - BS No – 012

All Nitrile type, hardness 70 shore.

Edited March 7, 2014 by hr369