TCM Fuel System

Tips on inspection and setup of TCM continuous flow fuel injection systems.


Remove, inspect, clean, and reinstall the aircraft and engine fuel screens in accordance with the aircraft manufacturer’s instructions. Inspect the induction air filter and alternate air system for condition, operation, and cleanliness. Inspect the aircraft vapor return system for proper operation. Ensure the fuel manifold valve vent and fuel pump drain lines are properly installed, open, and free of obstruction.

Inspect all engine control rod ends for wear, freedom of movement, proper installation, and security. Inspect the throttle and control assembly link rods (where used) for correct installation, security, and wear at the attach points. Ensure all engine controls operate freely throughout their full range of travel and are properly adjusted.

Lubricate all control rod ends and fuel system components in accordance with the latest revision of TCM Service Bulletin SB95-2 and the aircraft maintenance manual.

Locate the idle speed stop screw on the throttlebody and turn it counterclockwise two complete turns. (During fuel system adjustment, idle rpm will be controlled manually using the cockpit throttle control.)
Inspect the exhaust and induction systems for proper installation, security, and leaks. Inspect all lines, hoses, and wire bundles for chafing, loose connections, leaks, and stains. Fitzgerald offers an inspection tip for the fuel lines. “The rubber grommets around the fuel lines at the standoff brackets should be checked during any visual inspection,” he stresses. “It’s very important to make sure they are intact and that the steel fuel lines are not touching the metal brackets.”

Setup
SID97-3D outlines the setup process for performing the system test. During this step, the mechanic disconnects specific metered and unmetered fuel lines from the engine and attaches them to corresponding hoses and fittings going to the Porta Test Unit or to test gauges. The throttle control is positioned in the full open position and the mixture control is moved to full rich. The boost pump is turned on and all air is bled from the test unit and hoses using the instructions on the Porta Test Unit. If using gauges, the fittings are loosened at each gauge to bleed the lines of any air. (Hold the gauge at or slightly above the height of the fuel system component during the bleeding operation). Operate the boost pumps only long enough to complete the purging process. Turn boost pump off and verify that all lines, hoses, and fittings are secured and torqued and that there are no fuel leaks. Ensure that the test hoses are routed clear of the exhaust system and are adequately supported the entire length to avoid inaccurate gauge readings.

At this point, TCM stresses an important warning. “Make certain all fuel has drained from the induction system prior to attempting engine start. Failure to do so could cause hydraulic lock and subsequent engine failure.”

Install the engine cowling or cooling shroud for ground runs.

System test
Now you are ready for the fuel system test. Due to limited space, we don’t have the luxury to discuss the complete procedure. The test procedure is pretty straightforward. Start the engine and allow it to warm up and stabilize. You then will note the test gauge readings at idle and at full power (1,500 to 1,800 rpm) and record both the actual readings along with the specified readings on the operational test form on the last page of SID97-3D. The readings you will be recording include engine rpm, manifold air pressure, unmetered and metered fuel pressure, fuel flow, EGT, TIT, cylinder head temperature, and oil pressure and temperature.

If all readings are within the limits spelled out in SID97, the test is over. You can shut down the aircraft, disconnect the Porta Test Unit, re-connect all the fittings and leak check them, and re-cowl the engine.

Adjustment
If any of the actual readings are outside the specified limits, you will need to adjust the fuel system. Refer to SID97-3 for specific adjustment instructions. All adjustments are made with the engine shut down. Also, make all adjustments in small increments. Here is an overview of the fuel system adjustment procedure.

We Recommend

  • Article

    Teledyne Continuous Flow Fuel Injection

    Repair Stations Threatened Part 145 recommendations may shut you By Stephen P. Prentice March 2000 Stephen P. Prentice is an attorney whose practice involves FAA-NTSB issues. He...

  • Article

    Teledyne Continuous Flow Fuel Injection

    Repair Stations Threatened Part 145 recommendations may shut you By Stephen P. Prentice March 2000 Stephen P. Prentice is an attorney whose practice involves FAA-NTSB issues. He...

  • Article

    Continuous flow fuel injections systems

    Continuous Flow Fuel Injection Systems By Randy Knuteson November 1998 ontinental Motors calls it their "Continuous Flow Fuel Injection System." Some technicians refer to it in less...

  • Article

    Engine Compression Testing: Back to basics

    Engine Compression Back to basics By Joe Escobar Compression testing can be an effective tool for monitoring engine condition. Despite the apparent simplicity of the test, it can be a...