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Lycoming Fuel Pump (wobble style) Frequently Asked Questions
What is causing fluctuating fuel pressure Fluctuating fuel pressure can be the result of the following: 1. A worn fuel pressure gauge; 2. A worn or broken O-ring on the inlet side fuel fitting; 3. A defective fuel selector valve (boost pump may labor); 4. An obstruction in the induction system (air intake); 5. A clogged or dirty fuel strainer; 6. Foreign material inside the fuel body (such as fuel cell sealant, thread sealant, or a drill shaving) Low fuel pressure The most common reasons for low fuel flow/pressure are the following: 1. A worn or broken O-ring on the inlet side fuel fitting can cause an inlet suction leak. An inlet air leak will result in low Fuel Pump output pressure. 2. A weak operating spring in the Fuel Pump diaphragm assembly; 3. A worn fuel pressure gauge; 4. A clogged fuel vent or fuel cap; 5. A constriction in a fuel line either externally (a kinked hose), or internally (due to a collapsed hose lining). 6. Wrong fuel pump for the installation. Why is fuel or oil leaking from the fuel pump drain line? Leakage of fuel or oil through the fuel pump overboard drain line indicates a worn or ruptured diaphragm inside the fuel pump. The fuel pump should be replaced before further flight. Lycoming fuel pump won't fit on engine See the following Lycoming service instruction in Adobe Acrobat format:
S.I. 1110C Basically in 1978 AC changed the design of the pump making it slightly taller. You can use these later design pumps by modifying the engine per Lycoming Service Instruction 1110C. Early style pumps have a riveted, laminated rocker arm. Late style pumps have a "channeled" rocker arm. Early style pump: 40174/40295 low pressure, 40595 medium pressure, 40296 high pressure). Inspect your fuel pump for potential failure SPECIAL AIRWORTHINESS INFORMATION BULLETIN
 Aircraft Certification Service No. NE-01-22 May 11, 2001 Introduction This Special Airworthiness Information Bulletin (SAIB) alerts you an owner or operator of Textron Lycoming Division, AVCO Corporation (Textron Lycoming) O-235; O-290; O-340; (L)O and IO-320, -360, -540; AIO-320, -360; AEIO-320, -360, -540; HIO-360; and TO-360 series reciprocating engines, with fuel pumps, Part Number (P/N) LW-15472, P/N LW-15473, or P/N LW-16335 installed, and that has one of the manufacturing date codes listed below as scribed on the edge of the pump mounting flange. See Figure 1. These reciprocating engines are installed on but not limited to Aerospatiale, American Champion, Bellanca, Cessna, The New Piper Aircraft Company, Beech, Maule, Mooney, and Schweizer 269 series aircraft. Background Textron Lycoming has reported three events of high pressure fuel pump failures in their Production Test Cell. As of now, there have been no reported failures in the field and no way to predict when a failure may occur. The FAA is still investigating and if the situation changes, we may issue an Airworthiness Directive. These fuel pumps were either purchased as replacements or shipped from Textron Lycoming and installed on new, rebuilt and overhauled engines between September 18, 2000 and February 8, 2001 inclusive. The FAA recommends that you also check replacement fuel pumps received after February 8, 2001 whether they are installed or not. Textron Lycoming issued their Service Bulletin (SB) No. 548 determining that several lots of diaphragm-type fuel pumps may have a potential for an internal failure. When an internal failure occurs, the check valve seat separates from its shaft due to an inadequate or improper assembly crimp. This allows the liberated parts to move within the housing and may cause a blockage of fuel flow. This failure may not be evident on the exterior of the pump, but it may result in a decrease or loss of fuel flow and a corresponding decrease or loss of power. Textron Lycoming estimates that approximately 1,252 fuel pumps were manufactured between September 18, 2000 and February 18, 2001 with a potential to fail, but they can not predict if or when the failure may occur. Recommendations To prevent a failure of the Textron Lycoming fuel pump, P/N LW-15472,
LW-15473, or LW-16335, we highly recommend you inspect your engines for the
applicable fuel pumps as shown in Figure 1 below and replace it as described in
Textron Lycoming Service Bulletin (SB) No. 548. We recommend you should also
check your maintenance records for affected replacement fuel pumps received
after February 8, 2001. 3900 4000 4100 4200 4300 4400 Example: 163354800 should be inspected and replaced as specified in Textron Lycoming Service Bulletin 548 · If the letter “A” is marked as a suffix to the date code, the pump has been
repaired by the pump manufacturer and replacement is not necessary. |
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