Fuel reserve switch

[bramtr]

Hi!

This might be a silly question, but I'll take my chances. I have a 3 ltr P5 from the year 1964, and it has a switch on the dashboard for reserve fuel. It has two positions: in the middle, and to the right. And here is my question: what is 'normal' and what is 'reserve'?
I've just installed a refurbished dual fuel pump (as one of the steps to get the car starting normally, because it doesn't), and it seems that when the switch is in the middle, the fuel pump is in working order and not ticking (anymore), and when I put the switch to the right, I hear the pump (or better: one of the pumps) clicking without stopping. So now I'm inclined to think - since there isn't much petrol in the tank - that the reserve pump is in working order, and the other one will be clicking, since for that one the fuel level is too low. Which would mean that the switch on the dashboard is on 'reserve' when put in the middle, and on 'normal' when put to the right.

Do I make any sense? 

Regards,
Bram

[Phil Nottingham]

There is no reserve tank - the reserve is created with a concentric tank pick up with a shorter main tube and the reserve pump draws from the longer pickup which dips deeper in the tank. The main pump if operated when the tank is low ie under 2 gals will just pull air if operated. Only one pump operates on each switch position. The pump will tick every few seconds when the float chamber is full

[bramtr]

Sorry for my inconsistent messaging, I must have not been clear: I know there isn’t a separate reserve tank. And I could not read the letters properly, but now I see that reserve = switch to the right. So my theory as stated doesn’t stand 😕 The clicking stops on ‘main’, and keeps clicking on ‘reserve’ …

[Phil Nottingham]

You therefore need to check that the main pump is actually receiving 12v when in the centre position. There are separate switched feeds to each pump and there are bullet connectors inside the O/s A panel that can corrode if water leaks on them


Perhaps a simple On/OFF switch is fitted instead of a Changeover switch.  For  1964 P5 (ie Mk2c) the switch has 3 positions and is placed vertical. The Centre is Main, the Bottom is Reserve and the Top is sump oil level

Why not check if petrol flows when in the MAIN position by just loosening the fuel pipe at the sediment bowl in the engine compartment

[MK IA Norway Viking]

Apr 20, 2023 21:00:43 GMT Phil Nottingham said:

You therefore need to check that the main pump is actually receiving 12v when in the centre position. There are separate switched feeds to each pump and there are bullet connectors inside the O/s A panel that can corrode if water leaks on them


Perhaps a simple On/OFF switch is fitted instead of a Changeover switch.  For  1964 P5 (ie Mk2c) the switch has 3 positions and is placed vertical. The Centre is Main, the Bottom is Reserve and the Top is sump oil level

Why not check if petrol flows when in the MAIN position by just loosening the fuel pipe at the sediment bowl in the engine compartment

Gentlemen ... perhaps the two wires are swapped, so that the wire connected to one pump should have been connected to the other pump ? or, perhaps, the solenoid on the tank (if this is fitted to the MK II / MK III cars) is wired incorrectly ?

I propose to turn the ignition on, apply a test-lamp to the wire connected to one of the two pumps and see if there is power. If not, to flick the switch to the alternate position and see if there is now power. If one of the leads does not have power irrespective of the position of the switch then there is a fault with the power supply. That can either be repaired or arrange to give power to the pump that draw from the deepest suction in the tank.


Good luck !

[bramtr]

Thanks for all the advice! But the latest problem (and of course probably the cause of my issues): the (overhauled) pump seems to be leaking fuel! So today I will try to locate the cause for this, and Monday I have an appointment with the man that did the refurbishing. (And once I have the pump working correctly, I can proceed with looking for the cause of the very bad starting of the Rover. Never a dull moment  )

[Phil Nottingham]

Was the proper kit used to do each pump side (2 kits are needed) The external diaphragm screws may be loose. It is not a good idea to reuse the old diaphragms as unleaded fuel will have stiffened and OEM one and it will split and leak fuel.


It may just be a loose union as unless the pump casing is cracked or threads are stripped there is little scope for leaks  

[thor64]

Hi I too have a 64 3 litre and I was going to query your switch not being original. Mine, as Phil says, is three positions up / middle and down. I was a little unsure as to which position did what as the lettering is faint.  I need to sort out the reserve part of the pump. That is get it working but I can get by at the moment just relying on the fuel gauge and topping it up regularly. 

[break23m]

Apr 20, 2023 19:48:44 GMT Phil Nottingham said:

There is no reserve tank - the reserve is created with a concentric tank pick up with a shorter main tube and the reserve pump draws from the longer pickup which dips deeper in the tank. The main pump if operated when the tank is low ie under 2 gals will just pull air if operated. Only one pump operates on each switch position. The pump will tick every few seconds when the float chamber is full

I discovered recently that the moment the normal petrol suply stops, the reserve won't deliver either . A bit of a shame, I think this reserve option is great in case of emergency. So I have to check if there is a length difference between to two inside of the tank. Or bring a little jerrycan. 

[Phil Nottingham]

May 11, 2023 12:24:42 GMT break23m said:

Apr 20, 2023 19:48:44 GMT Phil Nottingham said:

There is no reserve tank - the reserve is created with a concentric tank pick up with a shorter main tube and the reserve pump draws from the longer pickup which dips deeper in the tank. The main pump if operated when the tank is low ie under 2 gals will just pull air if operated. Only one pump operates on each switch position. The pump will tick every few seconds when the float chamber is full

I discovered recently that the moment the normal petrol supply stops, the reserve won't deliver either . A bit of a shame, I think this reserve option is great in case of emergency. So I have to check if there is a length difference between to two inside of the tank. Or bring a little jerrycan. 

Is the reserve pump working? It is a twin ended one on the Mk2 - one for Main the other for Reserve

[break23m]

Yes, both pumps are working on my car. With fuel in the tank, on both positions of the switch the engine gets enough fuel. I checked the wires and the fuel pipes/hoses but everything is connected like it should.

[enigmas]

How hard can it be to check a power output to 2 independent wires from a dual position switch? All that is required by the complete novice is a 12v test light, a modicum of logical thinking and a patient, reasoned approach to the task.

It seems kind of obvious, with cars that have "systems" that are 50-60 plus years old, that most electrical issues will arise from poor electrical connections (dirty, high resistance contacts and grounds). Similarly, electric petrol pumps whether dual function or single if original, will need to be checked for viable operation. This can be done on a bench using the car's battery as a power source.

Spend the time, clean the switches and contact points and all ground/earth connections to bright steel, brass copper or whatever metal or alloy the electrical connection is made to. Do this with every independent circuit and the electrical dramas will cease. Do or check one circuit at a time, tick it off the list and move to the next circuit. Rome wasn't built in a day and neither will the electrical issues with a scatter gun method.

No electrical system repair is based on luck, do the basic research and spend the appropriate time rectifying the cause. You'll then be rewarded with a reliable car and a sense of achievement.