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Topic: Fuel Pump O ring installation (Read 563 times) previous topic - next topic

Fuel Pump O ring installation

Hi any hints and tips much appreciated. Trying to fit the main fuel pump into the undercar housing. It is a 1988 mk2 16v gone for one of the pro alloy housing as found original has been bodged multiple times and couldn’t source a decent original,ones I am struggling with fitting the o ring. I believe that the o ring is place above the flange on the pump housing. However the o ring does not want to go down into the housing far enough to enable the plastic retaining clip to sit flush with the housing. I have tried grease on the o ring and gradually tighting  each of the three retaining screws to get the retaining clip to push down the o ring . There is a slightly narrower diameter above the reservoir surface which I believe is where the o ring should sit and I am struggling to manoeuvre it into that so looks like o ring sitting to high? I am wondering if I have got order of installation wrong. I am putting strainer in first then pump with o ring over top flange on pump at electrics end so that retaining ring can hold down.Any experience would be much appreciated thanks

Re: Fuel Pump O ring installation

Reply #1 –
If I remember correctly, the o-ring (34) should go all the way up to the head of the pump (2) and be sandwiched between the pump housing (1) and the clamping ring (35).

So it sounds like you have the theory correct and are trying to fit it the right way.

But I'm not 100% sure if the clamping ring should fit fully flush, it may stand proud a little which is fine as long as the o-ring seals.





I do remember doing mine on my old one that it was a tight fit. But that was with a OE fuel pump housing.

So a couple of questions:

Are you refitting the original pump, or is it new?
If new is it a genuine Bosch one or aftermarket?

Is the o-ring new?
Is it genuine?
Is it the right size?
I belive the o-ring is NLA, if it's old could it have swollen from exposure to fuel?
If it's new it might not be the correct spec.
I belive it's a 5mm ring, rather than being a flat seal.

The final questions would be aimed at the Pro-alloy aftermarket housing and it might be worth sending them a message. I'm afraid I have no experience of these. It looks like there's a lip for the o-ring to sit on.



Do you still have the original housing? have you tried fitting up to that to compare how it all sits?

Re: Fuel Pump O ring installation

Reply #3 –
Quote from: Paul71 on
Hi any hints and tips much appreciated. Trying to fit the main fuel pump into the undercar housing. It is a 1988 mk2 16v gone for one of the pro alloy housing as found original has been bodged multiple times and couldn’t source a decent original,ones I am struggling with fitting the o ring. I believe that the o ring is place above the flange on the pump housing. However the o ring does not want to go down into the housing far enough to enable the plastic retaining clip to sit flush with the housing. I have tried grease on the o ring and gradually tighting  each of the three retaining screws to get the retaining clip to push down the o ring . There is a slightly narrower diameter above the reservoir surface which I believe is where the o ring should sit and I am struggling to manoeuvre it into that so looks like o ring sitting to high? I am wondering if I have got order of installation wrong. I am putting strainer in first then pump with o ring over top flange on pump at electrics end so that retaining ring can hold down.Any experience would be much appreciated thanks
The company that  fitted mine had it machined out to fit and had no further issues.
Ray

Re: Fuel Pump O ring installation

Reply #4 –
Thanks for all the useful advice. Managed to fit together and tightened down and all refitted to car. Was using Bosch pump and initially the o ring  supplied with the pump. Ordered genuine from vw classic parts but when it came it was identical. Just needed to persevere and tighten down the ring using quarter turns on each of the three bolts and it did settle flush . Pleased to say all working fine and much to my surprise no leaks! Thanks again