Square Base Fuel Pump Rebuild

Hello List,

Recently, the SU fuel pump installed by a previous owner failed after 20 years in service on my xk12O. On inspection I noticed it was a round body AUA 4080 installed on the chassis where the square body fuel pump is to go. Reviewing the archives I recall a post by Rob Reilly, I believe, that advised that these round body 4080 pumps are suitable for xk’s but need to be mounted on the firewall at the same level as the carburetors. I replaced the existing pump with a square body pump AUA152 from SNG. Looking at my spare used pumps I found another square body pump type 4644 with a tag on the diaphragm flange that reads AUA172 not AUA152 as I would have expected. I want to rebuild this pump but would like to know if it is suitable for the 120?

Secondly, I have another NOS round body pump AUA4080 with a tag on the diaphragm flange that reads AUB182. Is this normal? What car model would this be suitable for?

Any assistance offered by the list is appreciated, as usual.

Regards, Geoff

Site Search seems to be down at the moment, but I said the round body was used on SS and Mark IV, a single pump for 2-1/2 Litre and twin pumps for 3-1/2 Litre, mounted on the scuttle at carb level.
Here it is on my '38 SS 2-1/2 Litre.
Here is a 3-1/2 Litre Mark IV with what I believe are original type pumps.
Another with a later type.

Twin round bodies on the scuttle was tried on the prototype 120, which can be seen in Clausager’s 120 book, but must have been changed to the single LCS on the chassis before production began.

Someone recently posted a link to a Healey site which had a lot of SU bulletins, which probably has the information about different AUA models and applications. I have not had the chance to download it all yet.

Hi Geoff,

I made a few posts a few days ago about XK fuel pumps. Take a look at http://www.liblbc.info/images/SkinnerUnion/aua_212b.pdf. The non-square base numbers you give are HP pumps - but note 4080/4644 are the casting numbers of the base, not the pump code. Pump numbers that begin with a 1 are short coil versions of ones that do not have the 1. Thus, AUA 152 is short coil version of AUA 52.

You need any square base pump (LCS). Seems the AUA 172 specifies double outlet banjos, but the pump will be the same as AUA 152.


Continuing the discussion from Square Base Fuel Pump Rebuild:

Thanks Clive and Rob. I am sure these pumps were acquired by the previous owner as they have been in my spares for at least 20 years. I think I will rebuild the square base pump with one of the available kits. Thanks for the responses.

Regards, Geoff

Hi Geoff,

The rebuild kits contain expensive brass parts that probably do not need to be replaced. I have found it cheaper to order just the specific parts that were needed, such as valves, points/toggle, diaphragm, gaskets, etc.


for many years the company sold me the coil unit and electronics in either positive and negative earth very reasonably priced then chose not to just sell this separately. Then they suggested I buy a cheap pump round base pull off top and bolt to the dozens of rectangular bases I have, then they hiked the price of these pumps to billyO

Hi Terry, Good idea about the swap the top from the NOS round base pump which is AUB182 and put it on one of the square bases I have. Any concerns with this?

I downloaded all the SU bulletins on this Healey web site.
The original SU pump specified for all our XKs except late 150 was the LCS model AUA 57 (square body).
Late 150 was AUA 52, which was the same one, but with a condenser in the top, which helps the points last longer.
An alternate for all our XKs was AUF 301.
The testing bulletin AUA 213A gives testing data and diagrams of test stands in case you want to test one.

Flow rates in gallons per hour are presumably Imperial gallons.
Cut-off pressure of 2-3.8 psi is not defined in the document, but presumably is the point where the pump will stop when the float is holding the needle valve closed.
Any pressure higher than this might push the needle open and flood the carb.

For the last 25 years I’ve been running my original LCS pump with the 1990s version of the electronic transistor conversion, and never any trouble. Now I understand there is an even better printed circuit transistor conversion offered by Burlen and others.