12 replies to this topic

[gazza01]

Hi all.

 

I would like to know what the mechanical fuel pump is good for, as far as fuel supply for higher spec engines, carbs etc.

 

I have trawled the net and come up with no data, no facts, nothing at all.

 

All there seems to be is forum threads with people guessing, or quoting what they have read on a previous thread without any evidence.

 

Some say they are good for up to 90 bhp, some say 100 bhp.

 

Others say they had fuel starvation from the pump with 85 bhp, others say they reached 120 bhp without any issues.

 

I don't want to go over to an electric fuel pump just for the sake of it. They have safety issues which need sorting, which all costs

 

money.

 

My spec is 1330, stage 4 head with 36/31valves, 276 cam, 1.5 roller rockers, lightened flywheel, single 45 dcoe weber on 5 1/2 inch inlet.(being fitted at the moment)  and a stage 1 maniflow exhaust.

 

What I am looking for are the facts on these pumps.

Edited by gazza01, 08 January 2014 - 11:44 PM.

[grumpy dad]

Hi

I can tell you that the presure is 3.5 to 4 psi

but i don't know what the flow rate is

[Guess-Works.com]

The fuel pump you need is not directly related to horse power, so anyone who says good for upto x hp does not really have a clue....

 

The fuel pump you need is related to you carburettor or injection system, and how high you run the engine...

 

The std mechanical pump will service pretty much any engine running a single HIF44 carb, and most which are running twins.... It's only when you get into multiple big carbs like webers and bike carbs that you will need more fuel.

 

Forced induction systems the same as injection systems will require higher pressure pumps so the mechanical one becomes redundant....

[Gr4h4m]

 
Forced induction systems the same as injection systems will require higher pressure pumps so the mechanical one becomes redundant....

True for blow through/ traditional turbo systems. My suck through supercharger only needed 3 psi.

[Guess-Works.com]

 

 
Forced induction systems the same as injection systems will require higher pressure pumps so the mechanical one becomes redundant....

True for blow through/ traditional turbo systems. My suck through supercharger only needed 3 psi.

 

 

This is true for suck through, but did you use the mechanical pump ?

 

I should have added to that statement, higher volume

[maccers]

You can of course fit a fuel pressure regulator after the pump to fine tune the flow if needed, carb or injection.

[Dusky]

I have to dissagree on the fact of electric pumps being more expensive. They dont cost that much more + they are more reliable. A inertia switch of 5£ solves the danger...

[gazza01]

Yes but I already have the mechanical pump fitted and working?

[Dan]

  The standard pumps are meant to provide 11 gall/hr at 3.5 to 4 psi, but flow is engine speed dependant and they aren't designed specifically for Minis.  They are made for a range of cars so they may not get up to 11 gallons at the normal average engine speed range of our cars.  Of course most of these pumps will have been replaced at some time and if you have a pattern pump fitted rather than the genuine SU one it will only be made to exceed the minimum requirement and might not be to the exact same spec.

[gazza01]

Does anyone know why the mechanical pump azx1817 seems to have been discontinued, as this is supposed to be for 1275 with hif 44 carb.

[Jordan18]

Is there a difference in the fuel pumps on an a series engine and an a+? I'm trying to use my a+ fuel pump from a 998 on my 1275 a series and they won't fit properly as in the black bar is too long. Or am I putting the fuel pump in wrong?

Thanks

[nicklouse]

you are using the spacer?

[tiger99]

Which is there to provide heat insulation. Without it the fuel may boil and cause vapour lock. And, because the pump and camshaft are designed for it to be there, omitting it will usually break the pump but may damage the camshaft. But as it doesn't want to fit, it seems that no damage has been done here. Unlike the THOUSANDS of A series engine users in the 1950s and 1960s (A35 etc) who did their own maintenance, badly, and got the pump lever to go up behind the camshaft...