We have assembled a list of frequently asked questions about fuel pumps and supporting tech. Whether it’s about part numbers or settings, you’ll find the most popular questions and answers below. If you don’t see your question, please contact our product support department.
Yes, just cut the safety tie securing the adjusting stop nut. Make all adjustments IAW the engine and/or aircraft manufacturer’s maintenance manual. Remember to re-safety the adjustment stop nut prior to flight.
Please see Lycoming Service Instruction SI 1533C (or current rev).
The relief valve bypasses excess fuel back to the pump inlet after a specific fuel pressure has been reached. This assures a sufficient supply of fuel to the servo at all engine power settings.
The bypass valve is in parallel with the pumping elements. It is held closed by the fuel discharge pressure when the engine is running but provides a fuel flow path when the pump is inoperative. This allows fuel flow to the servo for engine priming, auxiliary fuel pump operation or fuel pump failure.
Yes, always coat the drive splines with molybdenum disulfide grease prior to installation. Please use Lycoming Service Instruction SI 1420 for additional guidance.
1. Contamination between the poppet and the seat. Flush and re-test the pump.
2. Vapor locking – verify fuel line routing and proper fire sleeve installation.
3. Damaged pump blades – typically caused by internal FOD.
4. Air leaks in reference lines – verify condition and line B-nut torque.
1. Relief valve is sticking open – verify a weak or broken spring.
2. Damaged pump blades – typically caused by internal FOD.
3. Erroneous gauge readings – verify with known good gages.
1. There may be a faulty or improperly installed rotor shaft seal.
2. There may be rust on the shaft that has damaged the rotor shaft seal. This it typically caused by the gear coupling spline not be properly lubricated at installation.
3. There may be a leaking diaphragm.
Please see the product line home page, select “Support” and then “Warranty”.
Please see the product line home page, select “Support” and then “Warranty”.
If parts and/or labor are approved under the commercial portion of the ASB or SB, complete the claim form at the end of the bulletin and return to the physical or email address provided in the ASB or SB.
Within 12 months from date of invoice, any unit returned for core shall be as removed from the aircraft, be complete and not disassembled. The core must be identified with an original data tag. Missing data tags or original ink-stamped identification will not be accepted. A percentage of the core value will be charged for all missing or damaged parts.
Any product returned for warranty consideration shall be as removed from the aircraft, be complete and not disassembled. All external parts including, but not limited to, brackets, fittings, bafflings, etc. shall be removed prior to shipment as they will not be returned.
Go to the hartzell.aero website and select Videos under the Resources heading.
