Can I shut the fuel supply off?

Hi

I have aquired all the parts required to convert to lpg. The system is fully working and off of a v8 twin carb disco. All that I need to change is the gas hose to the carb as it has a T in it for 2 carbs.... easy (And the small matter of tuning it!).

Right now the fun begins.

With the in cab switcher selected to petrol it shuts the gas solonoid and opens the petrol one.

With it switched to gas it shuts the petrol solonoid and opens the gas one.

I am worried at this point as to what will happen to the mechanical fuel pump which is driven off of the engine that will keep running. Will it damage the diaphram / over pressure the fuel line or carb? This system on the series does not appear to have a flow return from the carb so what will happen???

Any ideas?

Cheers

Mark

The pump will be fine just as it is.

It is a DEMAND pump, and once it has reached its maximum pressure, which is only about 3 psi and will happen in a split second, it shortens the stroke of pumping almost to nothing. It simply does enough to keep about 3psi pressure, which when no fuel is being pumped out, takes no effort at all.

The pump will NOT build up pressure. It CAN NOT do that. The cam lever does NOT PUMP the petrol - the cam lever only pulls the diaphragm back, and it is a SPRING which presses under the diaphragm and thus PUMPS the petrol out. If no petrol goes out, the cam-lever pulls the diaphragm down, and it more or less stays down because unless the petrol goes out (to the carb) the slight pressure of the petrol just holds it down.

Basically, if no petrol is flowing the pump is doing nothing, other than lying in wait with 3 psi pressure just in case you switch over.

It is worth keeping in mind that the petrol pipe up to the change-over valve will be pressurised at about 3 psi with petrol. Keep an eye on it.

CharlesY

Thanks Charles. Much appreciated and panic over now I know nothing will explode (fuel pump and fuel line wise any way!) Now to just put that 128lt of highly flamable liquid under preasure into my landy.... anyone got a light?

Disco Inferno said:

Thanks Charles. Much appreciated and panic over now I know nothing will explode (fuel pump and fuel line wise any way!) Now to just put that 128lt of highly flamable liquid under preasure into my landy.... anyone got a light?

Click to expand...

WAIT!! I need to get my video camera ready .... from a great distance .... !