Morris Minor Owners Club

Not sure if it's a coincidence, but in the very hot weather of these days.... coupled with the constant traffic jam in Lancaster, the petrol pump has been running in a demented & irregular fashion.

Prior, it had a steady beat which varied with the degree of accelerator pressure.

I could wait & see what happens when the weather goes back to normal, but meanwhile I wonder if this "phenomenon" is common.

The engine runs as normal & doesn't seem to be using excessive fuel.

Chris

Sounds like fuel vaporisation. When the engine bay gets too hot the fuel evaporates so the pump has to work harder to suck it up. It is a common problem and usually happens when stuck in traffic on a hot day so if the engine is running normally it doesn't sound as if there is anything to worry about. 'Normal' weather is due to return next week so wait to see if the problem continues!

No coincidence at all, direct relationship!

As it only happened under extreme provocation, very hot weather AND very slow traffic, I wouldn't worry too much about it.

Some cars will suffer much more easily.

As Louise says, normal weather is due to be resumed

If you have a fuel filter - that makes matters much worse..... The solution is to mount the pump lower down in the engine bay so it has 'flooded suction' from the tank. But if the car is still going ok - just leave it as is.

It is a particular problem with the side valve Series MM where the fuel pipe runs very close to the exhaust pipe. The solution in that case is to insulate or move the fuel pipe and to fit an insulating gasket between the carb and manifold

The evaporation occurs in the supply pipe to the pump - not in the carb , at least not when the engine is running. Yes when it stops, the heat may then soak back into the carb causing the fuel to evaporate - but while the engine is running the vapourising fuel in the jet bridge area keeps it all plenty cool !

Many thanks for the replies!

I went out this morning when it was not yet very hot & also the traffic wasn't too bad...normal ticking was resumed.

On the basis of the advice, I will leave alone & put up with the occasional machine gun sound effects.

Oddly, this new car (4 door) is the only one in which the petrol pump is clearly audible from inside the car.


regards

Chris

I had been wondering why the fuel pump was getting so excited this week. Very loud ticking, I had visions of only getting about 10 MPG! Very pleased to read that it is nothing to worry about. Must insulate my bulkhead then I won't hear it so clearly!
Mike[frame][/frame]

[quote="bmcecosse"]The evaporation occurs in the supply pipe to the pump - not in the carb

It is a well established fact that on the USHM2 engine the carb is bolted to the manifold with only a thin gasket between, and also the carb float chamber is at the back near to the exhaust, causing poor running in hot weather. The USHM3 engine has the float chamber at the front and a thick bakalite spacer between the carb and manifold.
USHM2 owners who have fitted a spacer have reported a significant improvement in hot weather running

mike.perry wrote:

bmcecosse wrote:The evaporation occurs in the supply pipe to the pump - not in the carb

It is a well established fact that on the USHM2 engine the carb is bolted to the manifold with only a thin gasket between, and also the carb float chamber is at the back near to the exhaust, causing poor running in hot weather. The USHM3 engine has the float chamber at the front and a thick bakalite spacer between the carb and manifold.
USHM2 owners who have fitted a spacer have reported a significant improvement in hot weather running

Both absolutely correct! It is the vapourisation in the supply pipe that causes the pump to whiz, which is the subject of this thread.

I've wrapped some insulation around the fuel supply pipe to the pump, which seems to have ameliorated the problem (though not entirely eradicated it).

Hmmnn, interesting...

A couple of times this week my car has exhibited signs of fuel starvation under load, both times shortly after restarting after a run, accompanied by madly ticking pump. Just slowing down to near idle was enough for it to pick up again to resume normal service. Has been very hot in Suffolk this last week, so have assumed the increased heat at standstill with engine not running was the problem.
Due to the car being off the road for 20 yrs before I put it back on again I have 2 fuel filters: 1 before the pump and 1 before the carb to ensure no muck gets in anywhere. The 1 between pump and carb seemed a bit empty at idle this afternoon and the fuel pipe felt very warm! Other than this the filters seem not a problem with no adverse signs evident 9 months after fitting.

Paul

You should definitely remove the filter BEFORE the pump. The pump already has a filter in the base - I suggest you should clean it too.