SIII leaky fuel pump

[PeterE]

Hi,

I'm experiencing repeated leaks from my fuel pump which on the SIII is a dual chamber SU AUF406/AZX1400 tucked inside the RH rear wheel arch.

Some history: I rebuilt the pump four years ago when I was having some fuel supply issues, it had seen a lot of service so I gave it the full Burlen service kit treatment, replacing all the key components including the mechanical points; testing back on the car delivers around 2.8 psi measured at the cross-carburettor fuel rail and an open-ended flowrate in excess of 2 litres a minute - well within spec - since doing this the engine has run fine with no fueling issues even with my foot flat on the floor :D.

However, I have had to replace the air bottle cork gasket (item 43 in the attached ROM diagram) every six months or so because it starts to leak around the retaining screw where it goes through the cover (items 44).



What appears to be happening is that the gasket changes shape (see before and after gaskets in photo) and the central hole where the retaining screw goes expands to the point that fuel then leaks past the retaining screw, the only fix is a new gasket (I have a large stock of them!). I'm pretty sure the car had this issue before I purchased it as the Hardura mat below the spare wheel is partially eroded.

Has anyone else experienced this issue? I believe the 4.2 litre S1/2 cars have a single chamber AUF301/AZX1308 which also has the same air bottle and gasket.

It occurs to me that an 'air bottle' should possibly not have fuel in it but I can't see how this could be the case with the way the internals of the pump are designed.

Anything to do with ethanol in the fuel? The car is only filled with Shell V Power (up to 5% ethanol I believe) and when layed up during the winter has Miller's EPS in the tank and fuel system.

Thanks...

[rolando38]

in my view it's more a mechanical constraint (vibrations, bad in this case...) than a chemical erosion
I'm not sure how it is secured but is there a more secure way to fasten it so it doesn't move at all ? (like silent block + jubilee or ...)

[Woolfi]

http://www.ebay.co.uk/itm/Hardi-Fuel-Su ... 56661c4155

I had also problems with the SU pump of my EV12. This Hardi 18812 fuel-pump solved all probelms immediately. Cheap and long lasting.

Regards Wolfgang Gatza

[PeterE]

Many thanks for feedback Rolando and Woolfi.

I'm absolutely certain that the problem is one of chemical reaction (I spent the first 20 years of employment as a research chemist and I still remember much of what was hammered into my thick skull during my degree studies :?).

I'm keen to keep the pump as original but take the point that there are better modern solutions available.

Marcus has fitted a new cork washer to his SIII fuel pump so we are comparing performance over time.

I have fabricated a new washer from a sheet of thin PTFE so will try fitting that next time the cork one leaks and will report back.