Morris Minor Owners Club

What causes the pump to work so erratically? It works fine then nothing, gentle tap and hey presto for a mile or so then same problem, then possibly good for the next week. Have cleaned filter and points etc what else can I do or is it the carb. It is off a 1300 metro.

It sounds like a fuel line vacuum... I have similar problems....the union joint on the fuel tank side seems to leak air and so causes a bubble in the line...it's one of tose jobs that seem to be 'I'll do it next time!'.

The problem might also be related to where the pump is mounted. The original Minor pump is designed as a 'pulling' pump: to pull fuel up from the fuel tank. Although I'm not familiar with the Metro pump location, I assume it's in the same spot as a Mini which would make it a 'pushing' pump: pushing from the fuel tank.
I know that if the pump is fitted in the wrong spot it can overwork/overheat it possilbly resulting in intermittent operation/failure though it would take more than a mile to do this.
More than likely the problem will be in the points. If you can remove the points cover when the pump has failed, try lifting or closing the removable point 'tang'. If this works then the 'tang' might need a little reshaping to obtain the 'correct' points operation. Not quite in the workshop manual but it's worked for me over the last 20 years.
Good luck.

I had the same problem with an MG midget, I moved
the original 'pusher'pump up to the engine compartment,
so it became a 'puller' and it never worked properly again!
Certainly worth checking where the Metro type was fitted
originally.

Tried a spare pump out of another Moggy and same problem, fills float chamber, drive off empty float chamber van stops, hit pump, clicks away merrily, fills float chamber, drive off, repeat till bored...

you could have a weak diaphram, air leak or the wire supplying power may be broken inside the insulation only making contact now and then.

Since you have tried two pumps with the same results it may
be worth running a lead straight from the unearthed side of
the battery to the pump contact and see if things improve.

Was the spare pump sitting around unused? They can get an oxide layer over the points whch weakens their effectiveness. I have always had teething problems with pumps that were unused for a while.
As it starts working after you tap it, that really does sound like points!
I replaced my points with some twin contacts out of an MG pump, but a replacement set of standard points should be fine also.
Normally with an air leak (in the petrol line from the tank) the pump runs faster, or non stop.

If you are 100% sure the points are good, then a simple test is to loosen the fuel line at the carb (when it has stopped). If the fuel still doesn't pump, then it is nothing to do with the carb. If it does restart then it's either the carb or weak pumping. If it restarts then fuel is likely to spit out of the loosened pipe, so don't smoke when doing that..

Willie mentioned 'hot wiring' it. If you run a wire from the battery. Its often a good idea to add a fuse when doing that.
If this cures it, then it is possible that there is an intermittent fault (open circuit) in the wiring, or there is high resistance in the wiring somewhere, which would make the pump more likely to stall.

I have the worse possible outcome of this problem, it now works perfectly so that frustrating fault has disapeared as quickly as it arrived.

Thanks one and all for your theories though.

In my experience, when I pump needs a knock its always the points. If you need proof, while the fault is there, carefully take off the cover, connect the live wire again, and prove you still have the problem (no pumping when ignition is on). Then short the points (briefly so as not to burn out the solenoid). You will probably find that the pump will give a few pumps.

Changing the points is not too hard. Just fiddly.

The old points used to have just one contact point. The new ones have two, and surprisingly don't last as long.

Cheers,

Chris.

The new ones have two, and surprisingly don't last as long.

Oh! so it wasn't worth the effort to fit twin points in the pump then?
Well if it lasts 20 years instead of 30 I wont worry too much.

Daddsie - did the fault dissapear with the 'spare' pump that you had fitted? That sounds like 6teeting probl;ems with the points and they have probably cleaned themselves.
The points should be inspected at least once a year (more often if you do high mileage) If they are looking badly eroded it is worth replacing them to avoid having to tap the pump in the near future.

My original ones lasted over 10 years without even a clean. The next lasted 3! They let me down on the M6, near junction 8 in rush hour!

I now clean em every now and then.

Chris.