5 replies to this topic

[p.b.r.]

1988 mini. Mechanical fuel pump
The pump is pumping fuel out the overflow tube and stalling the engine. The seat and needle in the float bowl have been replaced.
Why does the pump keep over pumping.

[nicklouse]

It always pumps.

If the seat and needle gave been replaced. Then you have a number of things to consider.

They were fitted incorrectly.

They are damaged or faulty.

Or the float is faulty/damaged.

[p.b.r.]

The seat and needle are fitted correctly, lt is a simple screw in.
The parts were purchased from Moss so should be of good quality.
The float is simple, no adjustments,

When the pump keeps pumping, and the float shuts the flow off, where does the fuel go. There is no return hose back to the tank?

[nicklouse]

It does not go anywhere the float presses on the needle shutting it off.

Like I said if you have fuel coming out of your overflow it is getting past your needle valve.

So see above.

[neal]

When I rebuilt my twin carbs I had the same problem, I found that there were small burrs in the brass needle valves from the machining process which were not allowing the viton tipped needles to seal properly, might be worth checking. This was a Burlen SU kit!

 

Might be worth checking your float height as well, the setting clearance info is in the Haynes workshop manual. You mentioned that there is no adjustment to the float height (I'm assuming that this is an external float bowl with the plastic float)  but I'm pretty sure you do this by shimming the needle valve, again well worth checking the Haynes Manual. I know that some have used fibre washers, I used brass ones or you may still be able to get hold of some shim washers.

Edited by neal, 01 October 2016 - 06:03 PM.

[Spider]

I've had a few mechanical pumps in recent years increase in output pressure over time. I haven't stripped them to see why, I just went electric. Last one had just on 7 PSI !