Fuel pump problems?

[billp]

Having browsed this index looking to see if my question has been answered previously - please excuse me if it has. Each time I've browsed I've been sidetracked by many other interesting subjects - so - here goes with mine:

I have a straight forward Dyane engined 223 with the correct Solex carb. After not using my Lomax for several months or so (ok - maybe I should get out a bit more) I find that the carb is empty of fuel and it takes quite a bit of cranking to get the motor to fire up. I worry a tad at each time that it happens, but the engine does always kick into life - eventually. Why? If there was fuel in the carb then the engine should start up, so the fuel must have evaporated. The pump seems to also be dry, yet I can't see why fuel in the line would drain back to the tank as the pump is not at that much higher a level than the tank, so the fuel line, below the tank level should contain liquid. I was told that there is a non-return valve in the pump that deteriorates with age, but don't know about that. Is my pump getting tried, I wonder? It works fine when running. I'm curious as to why the fuel evaporates from the carb and why the pump seems to take so long to pump up and fill the carb enough for the engine to start. Anyone have any ideas why this happens. No doubt there are many solutions, all suggestions are welcome.

[administrator]

Hi. Fuel pump uses poppit valves - which leak when they get old. Fuel drains out of pump back into fuel line.

Wen cranking after a few weeks, the pump is pumping air - which it doesn't do very well -so takes a long time.

Quick fix is to remove hose to carb and suck fuel thrugh pump - which will then pump fine. it helps to have a fuel filter fitted above pump so that you don't get a mouthfull of fuel

Alternatively, fit an aftermarket non-return valve below pump - restoring its action.

seen fuel bulbs fitted above pump - a couple of squeezes to fill bulb sorts things out.

carb is open to atmosphere - so will evaporate eventually.

of course, the real fix....is the use your car evey few days - if not morwe frequently.

Rgrds
Callum

[billp]

Thanks Callum, that all makes sense. A non return valve seems like the solution and they are easy to fit. I suppose that I could fit a new fuel pump as I have one of them.

Cheers

[Vyv Cox]

My fuel pump is new but I find similar symptoms, an evident lack of fuel to the engine after a period of a couple of weeks without running. I recently towed the car on a trailer to Spain and the same problem occurred when I tried to start it. I doubt that evaporation could be the cause - where would the evaporated fuel exit the carb?
Other than that the engine runs beautifully.

[howardjs]

Or fit an electric pump. This is a refurbed SU as fitted to Morris 1000's etc. but there are several aftermarket pumps available from the likes of CBS etc.
Works perfectly and with a reassuring clicking sound when you switch on the ignition, no moor engine cranking needed.
Howard

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[hutchii]

No matter how long the gaps between running I use a good squirt of "Easy Start " into the air filter.
Works without fail.

[llanigraham]

My fuel pump is new but I find similar symptoms, an evident lack of fuel to the engine after a period of a couple of weeks without running. I recently towed the car on a trailer to Spain and the same problem occurred when I tried to start it. I doubt that evaporation could be the cause - where would the evaporated fuel exit the carb?
Other than that the engine runs beautifully.

A carb is not sealed from the outside air. If it was it wouldn't work, as it mixes the petrol with the air, so that is where it evaporates to.

[hutchii]

Hi
Even after a long gap between running I've found that "Easy Start" works like a dream!
One 2 second spin to give the oil a chance and then a good squirt into the air filter, and off she goes!
Not failed me yet.

[llanigraham]

It might make it start easily, but it's long term use is not good for any engine.
If the engine doesn't start correctly then you would be much better finding and curing the problem properly.

[Vyv Cox]

There is no direct contact between fuel in the float chamber and external air. Fuel enters the chamber via the needle valve and leaves it by the jet at the bottom. There is a tiny vent to allow a dry chamber to fill with fuel but evaporation via this would take a very long time.