Fuel Pump Leaking at Electrical Connector - repair pictures and O ring sizes

[clarkd]

My fuel pump is part # 0 580 960009. It also is stamped with Germany and 952. Car is a 73 with Webers and pump puts out around 4 psi without a regulator. I’m not sure of original application for this pump.

Below are highlights from my repair steps with details that may help others.

Shot of fuel leaking around the electrical connector.


I referenced the thread below for disassembly.
MFI Open Heart Surgery II - The Fuel Pump

I’ll add that a lever worked better for me than a screw driver “un-staking” the can. I was digging into the soft metal too much with a screw driver and began using one arm on the thin pliers below on the can indentions. You can see an indention next to the electrical connector in the picture above. Magnetic pull is working against you when trying to separate the parts so don’t distort the can too much.

I deviated from the thread above in that I did not remove the top pump pieces prior to removing the can portion. The pump pieces have to come off at some point to get to the electrical connector, but not to replace the O ring that seals the can. You don’t have to disturb the “pumping section” if you are only replacing the can seal.
I also wanted to mention that there are bushings in the end parts that you don’t want to pound on. After removing the armature from the can, I used a punch and hammer to drive out the pump drive pin while supporting both ends of the shaft. There may be a creative way to press the pin out. I did use a vise to squeeze it back in.

Here is what you will see before the fun begins.


De-solder both electrical connectors at the brush housings.

Remove the retaining rings and slide off the brush assembly.

I’m not sure what the correct term is for how these parts were secured, but I used a Dremel to carefully grind away the metal above the washer on the ground side connector wire.

I twisted back and forth while pulling on the electrical connector to free it from the housing. Mine did not come out easily, and I was caught off guard when it finally came free. Be careful tugging on the connector. You don’t want to get this far and break a wire because you unintentionally snatched everything at once through the connector opening.

I thought there was supposed to be an O ring on the connector!

Upon closer inspection I found it!

I could not source a “square” O ring this size. I bought a 5/16”ID x 7/16”OD x 1/16”CS square O ring/washer and the ID and OD were good matches, but the width did not fill up the groove on the connector. It would have been a perfect fit with a 3/32” x 1/16” rectangular CS.

The 1/16” CS square O ring made a good seal, but I chose to use a fuel injector O ring (19/64” x 28/64”) instead. Below is a picture beside the original O ring. My thoughts were better long term resistance to fuel.

It came in a Dorman multipack part # 90100 from my FLAPS.

Putting things back together, I drilled (3/32”) then tapped with the smallest tap I had (4-40). I secured the ground connector with the original washer and an old hard drive screw.


I could not find the correct size O rings locally for the pump and can seals, but was able to get a good idea of the CS diameters I needed.
The O rings I used were Buna-N 70 designations from the O Ring Store.
The O-Ring Store LLC, We make getting O-Rings easy!
Shipping was more than the O rings, so I ordered different sizes I felt were in the ball park to test fit.
For the can seal, I used a 2.5mm CS diameter ring with a 50mm ID.
2.5mm X 50mm Metric Buna-N 70 O-ring (N2.50X050)
2.5mm X 50mm Metric Buna-N 70 O-Ring [N2.50X050] : The O-Ring Store LLC, We make getting O-Rings easy!
For the pump halves, I used 2.0mm CS diameter rings. For the base part on the left I used a 30mm ID O ring.
2mm X 30mm Metric Buna-N 70 O-ring (N2.00X030)
2mm X 30mm Metric Buna-N 70 O-ring [N2.00X030] : The O-Ring Store LLC, We make getting O-Rings easy!
For the top on the right I used a 32mm O ring.
2mm X 32mm Metric Buna-N 70 O-ring (N2.00X032)
2mm X 30mm Metric Buna-N 70 O-ring [N2.00X030] : The O-Ring Store LLC, We make getting O-Rings easy!
I believe 30mm ID would have worked for both parts, but I chose based on the squashed rings I removed. The important dimension is the 2.0mm CS diameter for these rings.


Good luck with your pump autopsies.

[E Sully]

Nice description of the job.

[Porboynz]

Great work, nicely documented. I must restore the 2 x leaky pumps I have sitting around.

[47silver]

i am putting a 72 pump back together and have a question on the armature thrust washers would you happen to have some photos or a diagram of where the washers and what type of washers go where?

[Mike O'Meara]

ClarkD - Thank you so much for posting o-ring sizes! Saved me much guess work and trial and error. Great!