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Petrol reserve

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rogerharrop
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Petrol reserve

Post by rogerharrop »

In a recent JDHT publication it says the B Spec SP250, which mine is, has a reserve petrol switch. If so - where is it?

Many thanks

Roger

Vortex O'Plinth
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Re: Petrol reserve

Post by Vortex O'Plinth »

If you've got one it should be mounted under the dash in the position arrowed red in this piccie......
fuel.jpg
It's a Lucas push/pull switch with a white translucent window that illuminates when the switch is pulled out.
Nick

"Don't bother with the Air & Space Museum - there's nothing to see.......".

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John-B
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Re: Petrol reserve

Post by John-B »

Vortex O'Plinth wrote: Sun Jan 26, 2020 3:21 pm It's a Lucas push/pull switch with a white translucent window that illuminates when the switch is pulled out.
... and presumably the petrol pump has to have two pipes of different lengths and two electrical connections, or are they all like this?

rogerharrop
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Re: Petrol reserve

Post by rogerharrop »

Many thanks Nick

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Re: Petrol reserve

Post by Vortex O'Plinth »

John-B wrote: Sun Jan 26, 2020 3:48 pm ... and presumably the petrol pump has to have two pipes of different lengths and two electrical connections, or are they all like this?
As you presume John, the reserve fuel tank fitting has two pick up tubes differing in length by about an inch or so. the fitting is shown on the tank in this pic.....
P1200342.JPG
The body of the unit houses a spring biased solenoid operated shuttle valve ported to the two pick-up tubes that extend into the tank. In normal operation the shorter of the two tubes draws fuel from the tank. As the fuel level drops and the short tube can no longer draw fuel, pulling out the dash mounted reserve fuel switch energises the solenoid and the valve moves to draw fuel from the longer tube. Those cars without the reserve fuel option have a single tube extending from the body which doesn't have a solenoid valve and no electrical connection.

If you have a reserve fuel unit and it doesn't seem to be working, air leakage into the pick up tubes is often the problem. These tubes are not extruded but folded from copper sheet and soldered along their length; it's the soldering that sometimes breaks down. If the solenoid or the valve is defunct they can be (expensively) repaired. New original units are not available.
Nick

"Don't bother with the Air & Space Museum - there's nothing to see.......".

faeton
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Re: Petrol reserve

Post by faeton »

The original tubes had gauze filter soldered to the bottom . My normal running tube split and I could only run with the reserve switch on ,, There was somebody in the club who made up a batch of pipes , Although a few years ago someone may know who it was , I have looked through my records with no luck ,
I never fitted the gauze back but fitted a line filter , no problem since, apart from ethanol damage which I have solved with a marine additive.

Dave

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Re: Petrol reserve

Post by Vortex O'Plinth »

faeton wrote: Sun Jan 26, 2020 7:30 pm
.....I never fitted the gauze back but fitted a line filter , no problem since.....
Dave
I think that's a good move Dave. I didn't refit the gauzes on my pick-up tubes either; if the gauzes do their job they will eventually become clogged and the unit will have to be removed to clean them. The solenoid valve is pretty robust and can usually pass bits of crud without jamming; however the fuel pump is more crud sensitive and the valves can become stuck if jammed with bits of dirt. I fitted an in-line washable fuel filter in the line between the tank and the fuel pump. This is easy to clean and with this filter protecting the pump and the original AC filter protecting the carbs, there should be minimal chance of fuel interruption.
Nick

"Don't bother with the Air & Space Museum - there's nothing to see.......".

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