Outline of the Series Land Rover fuel system operation.
In a Series Land Rover, petrol is pumped from the fuel tank by either a mechanical or electrical fuel pump. It is pumped to either a Solex or Zenith carburettor (2.25 litre engine) or to a Stromberg or SU carburettor (2.6 litre).
Air is drawn into the carburettor through an oil bath filter.
Some Series Land Rover models exported from the UK were fitted with air pollution controls, consisting of either crankcase ventilation, fuel evaporation control or exhaust emission control devices.

Petrol fumes - engine off
Damaged or corroded fuel pipes; loose pipe unions; leaking fuel tank.

Petrol fumes - engine idling
Leaking from unions between fuel pump and carburettor; wrong float level setting in carburettor causing overflow; hole in carburettor float; faulty needle valve.

High fuel consumption
A high fuel consumption is a fact of life in a Series Land Rover compared to most other 4x4's but you can check for: worn carburettor jets; wrong jet settings; linkage mechanism sticking or incorrectly set: blocked air filter; float level too high; choke stuck on.

Difficult starting - cold
A Series Land Rover will tend to start without the use of choke except in particularly cold conditions. For difficult starting under choked conditions check for: choke cable problem; fast idle adjustment incorrect; float level wrong; needle valve sticking open; hole in float; faulty fuel pump.

Difficult starting - hot
Choke still on; blocked air filter; float level too high; needle valve sticking; hole in float; faulty fuel pump.

Poor acceleration
A Series Land Rover does not really 'accelerate', at best, it slowly gets faster!
In Zenith carburettors: the acceleration pump, ball valve or non-return valve could be sticking;
In Solex carburettors: the non-return valve or accelerator jet could be blocked; pump diaphragm leaking; pump operating linkage not adjusted correctly; discharge tube ball valve seized.
In SU and Stromberg carburettors: no oil in the damper or too thin oil used; piston sticking.

Loss of power
In Zenith and Solex carburettors it could be blocked fuel jets or carburettor drillings.
Water in fuel could be the cause. If water is found in the float chamber then the entire fuel system of the Land Rover should be drained.

Stalling or poor idling
Float level too low or needle valve sticking; in Solex or Zenith carburettors the slow running setting could be wrong whereas in SU carburettors it could be an incorrect jet setting or the piston sticking;
air leaking through worn spindle or bearing; cracked or distorted inlet manifold or leaking gasket ; carburettor gasket leaking; vacuum advance pipe or connections leaking; vacuum servo pipes or connections leaking.