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 dignified terms, replete with colorful expletives. The...


If an engine continues to lope on at ICO, it can usually be attributed to either scored mixture valves in the metering unit or a manifold plunger that refuses to seat. Typically, if the engine runs on indefinitely, the problem can be attributed to scored mixture valves. However, if it continues to run for a short period, then the problem lies somewhere between the manifold valve and the cylinders. To further isolate the cause, remove the hose feeding the manifold valve at the metering unit outlet fitting. With the mixture valve against the ICO stop, engage the boost pump and look for any indication of fuel flow from this fitting. Be certain to capture any leaking fuel in a suitable container and use caution if the engine or exhaust is heat-soaked. Leakage in excess of 20 drops per minute at 10 psi of pressure is unacceptable. The metering unit should be sent in for repair. If you're still uncertain as to the cause, interrupt the hose feeding the manifold inlet and plumb a ball-valve between it and the metering unit. Then, with the engine running at idle speed, use the ball valve to manually cut off fuel flow to the divider. If the engine continues to run, the problem most likely rests at the manifold valve. Other contributing causes of poor idle cut off may stem from a leaking primer system — plugged or partially plugged injection nozzles, allowing the engine to run on residual fuel pooled in the induction, or in the case of a turbo-charged engine, a leaking aneroid seal that dumps fuel back into the upper-deck.

A fuel system that has been fine-tuned for a specific engine/airframe may require a periodic re-trimming. As the engine breaks in, and operating parameters change, and cockpit gauges lose their accuracy, it becomes necessary to perform a "check-up."

Continental encourages an "operational verification" any time an engine is installed, a 100 hr. or annual is performed, or whenever a fuel component is replaced or adjusted. This may seem "excessive," but it assures of a smooth running engine to TBO.

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