SU fuel Pump AUA66 (points) Overhaul Guide

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svenedin
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SU fuel Pump AUA66 (points) Overhaul Guide

Postby svenedin » Sat Sep 13, 2014 12:43 pm

I just thought I would make a post about fuel pumps. There are loads of posts about fuel pump problems but no thread encouraging people to do routine maintenance on the pump. My pump was an absolute nuisance for years and I always blamed it on the points. I just had the pump to bits and it was nothing to do with the points at all. The insides of the pump were coated in nasty sticky fuel residue and it was a miracle the pump worked at all. Petrol and a toothbrush did not remove the residue but carburettor cleaner was very effective. The disk type brass valves were completely stuck.

I found a good article on pump restoration by Cliff Knight here: http://www.mg-tabc.org/library/fuel_pump/supump2.html

Make sure you have all the replacement parts you might need before you take the pump to pieces. At an absolute minimum this will be the gaskets, fibre washers and sealing washer but you will probably want to replace the diaphragm and the points at the same time. It is silly to try to reuse an old gasket or washer because a petrol leak could be very dangerous. New rocker assemblies and blades from SU have twin points rather than the single point on old pumps so they should be more reliable. If you wish you can buy a kit to convert to electronic rather than points. I rather like the reassuring tick tick of the points type pump though.

A couple of things are not mentioned in the article: old pumps (like mine) appear to use asbestos gaskets so take due care with these and dispose of properly. New gaskets are not asbestos. Also, if your pump has brass rollers be careful when you take the diaphragm off -they will all fall out so don't lose them. It is essential that the diaphragm is adjusted correctly (see article) and that the pump is connected to power and the points held closed prior to completely tightening down all the screws. This ensures that the diaphragm is at its maximum forward throw when the pump reassembly is complete.

It took me about an hour to do the whole job which included taking the pump off, stripping down, reassembling and reinstalling. The difference is dramatic, it works perfectly now. I should have done this job years and years ago. Anyway, don't blame the pump for being rubbish. It isn't rubbish, it's beautifully designed but yours is probably long overdue an overhaul!

One other point, these pumps do not like dirty old fuel. I completely overhauled my pump and it stopped working just a week later. I cursed the pump for being useless but it was horribly stuck again because my petrol tank had such disgusting fuel in it. I drained all the fuel out of the tank from the drain at the bottom, rinsed out with fresh petrol and refilled. All is well again. Not as good as taking the tank out completely and cleaning it but it has worked for now.

Lastly, old pumps have diaphragms that were never designed to cope with modern fuels. The culprit here is probably the ethanol that has been added to petrol. Current UK petrol (E5) has 5% ethanol but up to 10% (E10) is now allowed. This is an EU "eco" directive. It's madness because rainforest is being cut down to grow crops to make ethanol but that's off topic. What's on topic is this ethanol attacks the rubber used in old fuel systems and also damages the alloy used in carbs etc. A new diaphragm will cope with modern fuel so it's best to change it.

All the parts from a tiny washer to a brand new pump are available from SU and there is also an overhaul kit with all the parts you need for a major overhaul.

Tudge
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Re: SU fuel Pump AUA66 (points) Overhaul Guide

Postby Tudge » Sat Sep 13, 2014 2:48 pm

Great find! Thanks very much, link is favourited.
1965 2Dr - She's called Lola


don58van
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Re: SU fuel Pump AUA66 (points) Overhaul Guide

Postby don58van » Sun Sep 14, 2014 2:37 am

Thanks so much for sharing!
Regards
Don

Old_Robin
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Re: SU fuel Pump AUA66 (points) Overhaul Guide

Postby Old_Robin » Thu Feb 26, 2015 10:18 am

Excellent posting. Thanks
Old-Robin
1955 Saloon, 803cc. MMOC Oxon & Berks Branch


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