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Part # 41452
FAA-PMA for Lycoming or Continental Engines
Related Service Bulletins:
Tempest has the most extensive offering of FAA approved new and overhauled Lycoming diaphragm fuel pumps available. These new pumps use a cast housing and channel arm design. All overhauled fuel pumps internal parts are replaced with new certified parts. The actuating arms are magnetic particle test inspected; cast parts are inspected for wear, corrosion, and cracks. Overhaul is available for both the older laminated and newer channel style fuel pumps for normally aspirated, pressure carburetor and fuel injected systems.
The Early Model Lycoming Fuel Pump (40174/40295 low pressure, 40595 medium pressure, 40296 high pressure)
In the spring of 1964, AC introduced the first dual diaphragm type fuel pumps. These pumps were the first models to incorporate the oil seal integrated with the upper diaphragm and a separator ring for installation of the vent/overboard drain line. These pumps are characterized by a rocker arm which is an early riveted, laminated design. Current production in Lycoming pumps will not fit some pre-1978 applications without expensive modifications. You can eliminate the need for these modifications by ordering an FAA Approved overhauled early model pump for direct replacement.
The Late Model Lycoming Fuel Pump
In August of 1978, AC introduced what is now known as the “late model” fuel pump which has a “channeled” rocker arm. This pump is taller than the early laminated arm pump and has a unitized diaphragm assembly. Because of its increased size some pre-1978 model aircraft require expensive and time-consuming modifications to carburetors or accessory housings (ref: Lycoming Service Inst. No. 1110C). These modifications are not required if the smaller, early model laminated fuel pumps are installed on your aircraft.
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I have just installed my new Fuel Pump and my engine will not start. Why?
A common cause for this problem is fuel starvation due to improper installation of the fuel pump. Make sure that the fuel lines are not crossed; that is, the inlet line should be connected to the inlet side of the pump (marked “IN” on the top of the port) and the outlet line should be attached to the fuel pump outlet port. Fuel should be present at the inlet side of the fuel pump.
Improper installation of the fuel pump may result in a misalignment of the operating lever with the operating plunger in the accessory case. If so, there will be no movement of the lever and no pumping motion to provide fuel flow. If misalignment is found upon removal of the pump, the lever is probably damaged or broken. If misalignment of the operating lever has occurred, it will require inspection and repair by a qualified technician.
What is causing the fuel (or oil) to leak from my Fuel Pump drain line?
Leaking fuel or oil through the fuel pump overboard drain line indicates the rotary seal is running dry or contamination happened in the field. Your fuel pump should be replaced before further flight.
What is causing my fuel pressure to fall below the “green arc”?
The most common reasons for low fuel flow/pressure are the following:
What is causing my fuel pressure to fluctuate?
Fluctuating fuel pressure can be the result of the following:
Is there a mandatory replacement time for diaphragm fuel pumps?
Diaphragm fuel pumps should be replaced or overhauled:
How do I keep contaminants out of my fuel system?
The fuel selector valve works in unscreened fuel. Contaminated fuel can cause selector valve seal damage. When fueling from possibly contaminated fuel sources McFarlane recommends the use of a fuel filter, such as Mr. Funnel or another filtering device, to reduce trash in the fuel system.