More unknown pipes!

[Ceejay 72]

Following on from my post a few days ago about "unknown pipe at fuel tank", I today removed the fuel pump to try to track the fuel smell in the boot. Horrible mixture of decaying fibre washers mixed with oversized copper washers sealing the banjos. Has anyone tried using copper or alloy washers to seal the banjos - or is fibre the only answer?

My next unknown pipe question though is I found on the SU pump two small spigot pipes - one at the cap end and one at the other end of the casing by the diaphragm chamber. These look as if they are intended to be fitted with small diameter flexible pipes, but aren't.
Does anyone know what these small pipes are for?

Thanks,
Chris

[Lingen]

Chris. I have occasionally seen them with small bore pipes on, but always open ended. I think they are just breathers for the internals of the pump.
Mike.

[nigele]

When I overhauled my original pump I used a 3/8 BSP self-centralising Dowty washer between the pump body and banjo, with a fibre washer under the bolt head. Later SU pumps have a recess in the body for an o ring rather than a flat face and washer.

Nigel

[dasadrew]

Following this thread and the other with great interest. My Stag has a distinct "fuelly" odour in the boot when the boot is closed overnight after a run. Have checked all pipes, connectors, elbows everything. Also, the pressure bleeds off overnight so that the fuel pump ticks a dozen or more times in the morning - this didn't happen when the car was freshly restored.

There is no obvious localisation of the smell - must be a very small amount. When the boot lid is open in the garage overnight there is no smell present next day.

The recent answers point me also in the direction of the banjos. As I am reluctant to pay postage on two "O" rings from UK can anyone post some dimensions and seal types so I can try and source something locally to play around with or one sopurce in UK which does all types of seals so I could put an order together?

Ta

Drew

[JOHNS]

Following this thread and the other with great interest. My Stag has a distinct "fuelly" odour in the boot when the boot is closed overnight after a run. Have checked all pipes, connectors, elbows everything. Also, the pressure bleeds off overnight so that the fuel pump ticks a dozen or more times in the morning - this didn't happen when the car was freshly restored.

There is no obvious localisation of the smell - must be a very small amount. When the boot lid is open in the garage overnight there is no smell present next day.

The recent answers point me also in the direction of the banjos. As I am reluctant to pay postage on two "O" rings from UK can anyone post some dimensions and seal types so I can try and source something locally to play around with or one sopurce in UK which does all types of seals so I could put an order together?

Ta

Drew

I agree with Nigel. See the p[ics below. My pump from a 1978 Stag does not have grooves for an o ring and as such the best solution is a dowty seal netween the banjo and the pump face-see attached pic. An o ring will not work without a groove as they are designed to be compressed between two flat faces with one face having a groove. The pics of the banjo fitting show a recess on the bolt head side. This is for a fibre washer which will compress with the bolt head. You can see from the pic of the banjo bolt the head is machined to fit that recess.

DOWTY WASHER.png
FUEL PUMP.JPG


BANJO.JPG

[dasadrew]

Thanks John, any idea on sizes so I can order some locally?

Drew

[JOHNS]

Drew,
Nigel stated that he used a 3/8" BSP Dowty washer. From the Dowty charts the is seal no. 823. As you are in Germany it might be difficult to source imperial sizes. I checked the chairs and the nearest German metric equivalent is a 16mm seal no. 229. See website below

www.potterassoc.com › bonded_seal_information_and_sizing_chart

[dasadrew]

Cheers John, I'll follow that up

Drew

[JOHNS]

Try this link

bonded_seal_information_and_sizing_chart.pdf

[mallardstag]

Thanks John, any idea on sizes so I can order some locally?

Drew

It may be worth checking that whatever you use is suitable for E10 fuel.

[JOHNS]

Here is an extract from the results of a testing programme. Nitrile appears to be unaffected.
3. Results and Discussions

3.1. Visual Inspection

3.1.1. Elastomers

(a) WET Specimens. Neoprene, E10 specimens were found to be relatively very soft and brittle when compared to E5 and Air-55 specimens. Pits and depressions were also observed in E10 specimen (Figure 1(b)). For Nitrile, HNBR, and PVC/NBR specimens, no significant change was observed either in E5 or in E10 specimens.

(b) DRY Specimens. Neoprene, E10 specimens became hard as compared to E5 specimens. Shrinkage was also observed in the E10 and E5 specimens after drying. Pits and depressions in neoprene specimens (Figure 1(b)) kept in E10 fuel give an indication that material has leached out during exposure time, which can potentially cause problems in the fuel system and engine. Leaching of a product represents rapid degradation of the material since it can clog up other components. No shrinkage was observed in E10 specimens of Nitrile, HNBR, and PVC/NBR elastomers. Minor change in gloss was seen in HNBR and PVC/NBR specimens.

[dasadrew]

Thanks for all the info - just ordered 4-off 3/8" BSP in Germany for €9.90 incl. postage. In Germany, imperial sizes are normal for water and hydraulics, so getting a BSP size wasn't too difficult. I'll post results if it's a success and further questions if not!

Drew

[Phil S]

they should be good for s10 as they are used on petrol pumps

[nigele]

These were the ones I used:-

https://www.ebay.co.uk/itm/NBR-Bonded-Seal-3-8-BSP-Dowty-Washers-Self-Centralising/142314080563?hash=item2122948933:m:mOuux71bD0w53tadPiMaacA

It’s been fine for the last 2 1/2 years. Because the Dowty washer is thicker than a fibre washer, you loose a couple of threads engagement, but still tightened up fine, and did not need much force to get a good seal unlike the fibre washers.

Nigel

[dasadrew]

Just thought I'd follow up on this fuel smell thing.

I ordered up some Dowty seals, and simultaneously discovered some in an old SU Overhaul Kit that I had. Both were for 3/8" BSP but had different outer diameters.

Undid the banjo bolts and was quite surprised that, although they were tight, they released completely very quickly - not giving the impression that the compression of any seal was accompanying the release at all. Took all apart and had both a fibre washer on the bolt side and an 'O' ring on the pump side. Seals looked ok.

Tried to fit the Dowty seals, but the outer diameter is bigger than the recesses and so they sat on top of the lips. This meant there was hardly any bolt thread left. Nevertheless I assembled like that and switched on the pump - disasterous. Weird gurgling noises and continuous ticking. Obviously the banjo and bolt fuel holes weren't aligning.

Decided to order up some new parts and started measuring everything up and reading Jaguar and MG forums on the same problem.

The attached sketch shows what has been happening (at least in my case). The fibre washer is 1,5mm thick, which is the depth of the recess; the 'O' Ring has a 1mm dia. cross section which is the same as the depth of the recess. These seals are only just lightly contacting the metal surfaces which need to be sealed.

I've now ordered some slightly thicker 'O' Rings to try out and 2mm thick fibre washers. Of interest here is that Peter at LD Parts lists a 2mm Nylon washer as a replacement for the original fibre washer.

In the meantime, I made some 'O'Rings from NBR round cross section and doubled up the fibre washer. Hey presto! The overnight fuel smell in the boot is gone! Beats me how this mismatch of seals which don't protrude above the lip has occurred. It's an original SU Pump and has the original Banjos. I can only assume it's been a case of "Nearest Metric Equivalent" in Imperial machined parts.

Drew

Fuel Pump Banjo.jpg