Modifying an SU pump to operate by the fuel tank

[MikeNash]

Dear all,
Just curious, but I see from page 41 of the Jan/Feb Minor Matters that in a letter from Mr H Taberner (Technical Adviser Merseyside MMOC) the only difference between a suck pump and a push pump is the spring. So I can convert the pump's function by changing the spring. Is that really all? Regards, MikeN.

[Willie]

Well, he came over as knowing what he was talking about but if you are not confident ( I don't know where you would source the correct spring) then fit a pump from a suitable MGB or Midget as they were 'pushers'
instead of 'pullers'.

[Packedup]

Ive never seen one, but I seem to recall the electric pumps on Minis were pushers as well, just to ad to the list of potential alternatives

[rayofleamington]

Yes, Minis and MG's had the SU pusher type depending on age/model etc...

I've sold a few of these on ebay (2nd hand - I had a box full). If the part has a reference number, you can just type it into google and you'll often find which vehicle it was originally fitted to.
The pusher and puller pumps were modified over the years and therefore the numbers changed, but I've yet to find out if any were 'better' than others.

If you want to swap your Minor puller for an MG pusher, just let me know!

[JimK]

I'd be interested in doing that. I'm pretty sure the new engine will result in higher under-bonnet temperatures so if I can lower the likelihood of fuel vaporisation that sounds like a good thing.

[Kevin]

Normally when a pump is put by the tank the most commonly used type is the Facet pump which are quite a bit cheaper than the original type pumps.

[bmcecosse]

But they soon get covered in mud and salt - and stop working. Not a handy place for roadside repairs! The Mini mechanical pump works in all conditions - so if your block has a place for it - that's the way to go. Otherwise - consider just re mounting the normal electric sucker pump down on the floor of the engine compartment - it's the lift up to the pump that seems to cause some cars (never mine) the problems - so just eliminate the lift.

[8009STEVE]

Early Jags, XJ6 etc, had 2 pushers in the boot.

[bmcecosse]

^^^^^^ Double ended pusher much prized for use in Rally Minis.

[MikeNash]

As a matter of interest, my fairly new SU pump will lift fuel to a maximum of 60.5 inches. At this point its stalled, and so not delivering fuel. Taking 14.7 psi (one atmosphere) equal to 33.95 ft of water and petrol having a specific gravity of 0.78, then the pump achieves 2.18 psi.
With that lift a "suck" pump might work if down at the tank, even if its not the best choice. Regards, MikeN.

[Willie]

STEVE a minor point but my two XJ6 pumps were INSIDE the petrol tanks.

[paulhumphries]

STEVE a minor point but my two XJ6 pumps were INSIDE the petrol tanks.

I suppose it depend on the model.
I assume your was injection if they were in the tanks.
My 1976 3.4 (carbs) had twin pumps in the boot.

Paul Humphries.

[Willie]

OH, well they would be very suitable then as you say. Mine was an '81
3.4.

[MikeNash]

If you fit any of these various higher pressure pumps down at the tank does the standard carb float chamber cope without flooding? Or do you have to modify the needle and orifice therein? MikeN.

[Willie]

The float chamber valves and seats on the Midget were the same as for
the equivalent Minor engines so the answer would seem to be no.