Fuel pump problems will make themselves known most noticeably when the vehicle is accelerating or under heavy load - such as hill climbing. However, it is common practise for petrol-engined Series Land Rover owners to fit a paper fuel filter between the fuel pump and the carburettor.
The idea is to remove corrosion debris that managed to get through the tank and fuel pump's filters. This additional paper filter can become partially blocked and it is not possible to visually inspect it. Routine regular replacement is the best course of action.
So change this filter, if present, before removing and stripping the pump.
There are some checks that can be done with the fuel pump in situ.
Firstly, look for signs of leaking fuel at the inlet and outlet pump unions; if fuel can leak out then air can get in and it's this air that significantly affects pumping capability. Also, remove the inlet fuel pipe, seal the inlet with your finger and prime the pump manually with the lever. If significant suction is felt then the pump is probably OK but there could be a partially blocked gauze filter in the tank, a blocked air vent in the fuel cap or a leaking fuel union or damaged pipe between the tank and the pump.
Some Series Land Rovers have mechanical fuel pumps with a glass sediment bowl; this can be removed and inspected for sediment(see photo below). If sediment is present then there is an increased chance that the fuel pump filter
could be partially blocked.
A possible source of air leak is via the rubber seal on pumps that have a glass sediment bowl attached to the pump. The best way to check for seal leaks here and via the main top gasket is to remove the pump from the Land Rover, seal the outlet with your finger, prime the pump to build up pressure and then completely submerge the pump in kerosene and look for air bubbles. An air leak on the inlet side is the most effective in reducing pump efficiency.
With the pump removed it can be stripped and the rubber diaphragm carefully checked for holes, tears and lack of flexibility. The gauze filter can be removed and cleaned. The valve seals and seats can also be inspected for tiny particles affecting their proper closure. A pump overhaul kit for Series Land Rovers will contain all new valves, seals, gaskets, diaphragm and filter.
It's important to remember that the top of the pump is aluminium and so fixing screws should not be overtightened else the top casing can be distorted and cause air leaks.
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