Four Tips for Better Air Starter Engine Cranking

Ensuring engine startup using an air starter requires a few preventive measures that can help maximize engine up-time. When an engine fails to start, the all-important question is “what went wrong?” While keeping in mind that for an engine to start, essential elements other than the starter, namely fuel, oxygen, fire, compression, and exhaust are required. This guide will focus on the top four air starter errors and how to avoid them.

#1 – Starting sequence initiated while starter or engine is still rotating

Air starters and engines have run-down times. Depending on the type of starter it can take (5 to 20) seconds for an air starter to come to a complete stop. Larger displacement engines can also require 20 to 30 seconds to come to a complete stop. A rotating gear has trouble meshing with a stationary gear. Two rotating gears have double the trouble.

Result: Broken or chipped drive gear pinion

Result: Damaged starter clutch Result: Broken or sheared starter drive shaft.

The Fix: Always wait at least 30 seconds to initiate a cranking sequence following an aborted or failed start. Make certain that the engine and the starter are at complete stop.

#2 – Hard Crank Cycles

In ideal conditions, well-tuned engines will start quickly. Sometimes ideal conditions do not exist, and hard cranking cycles (20 to 90 seconds) are required to start the engine. Modern air starters are designed to handle these circumstances, but they can still overheat. Internal overheating will adversely affect vanes, bearings, and transmissions. Signs are pinion wear signatures. Heat signatures. Vanes can get hot enough to scorch or burn. Bearing over-heating can cause the bearing failure, resulting in the starter motor seizing. Result: Scorched or burned vanes that wear prematurely, break, splinter and will lock up the air motor Result: Drive bearing failure causing scorched or broken shaft.

Result: Turbine shaft bearing failure causing bearings to disintegrate and seize the turbine motor

Result: Pressure signature and gouging of drive pinion prevent smooth flywheel engagement.

Fix: If an engine fails to start, allow 2 to 3 minutes cooling time before initiating cranking cycle again.

#3 – Contaminated Air/Gas Stream

Clean air or gas will help keep air starters running smoothly for years and years. Modern air starters can tolerate limited amounts of dirty air such as water, oil, fluids, fine dirt, rust, and other contaminants, but eventually these take a toll.

Result: Eroded or deformed turbine rotors and nozzles

Result: Stuck vanes Result: Damaged motor bearings and metal components Result: Relay valve mechanism stuck or causing internal bleeding

Result: Starter drive control lines and control ports clogged, causing the starter drive to fail to engage the flywheel

Result: Starter drive permanently stuck in flywheel, causing the drive mechanism to continuously turn with a running engine.

The Fix: A) If a new install, blow out piping with air to remove welding slag, dirt, and rust before attaching starter. B) Inspect, clean or replace the relay valve as needed. C) Install a Y-strainer and mesh airline filter. D) Drain airlines prior to starting. Especially, if the starting system has been idle for long periods. E) Clean and blow out control lines and ports. F) Be sure to orient the starter exhaust downward, so any fluids or debris can escape easily.

#4 – Insufficient and Pulsating Air/Gas Volume

Air/gas pressure (psi/bar) is vitally important, but air/gas volume is often the real culprit when air-starting engines.

Result: Low starting power output

Result: Pulsating volume caused by obstructions and unnecessary piping elbows can damage starter transmissions and result in failed starts.

Fix: A) Consult manual or manufacturer for correct supply line size. B) Eliminate piping elbows. C) Check the exhaust port and piping for obstructions like ice, too small piping, and eliminate 90-degree elbows.

By following these tips, you can enhance the reliability and efficiency of your air starter engine cranking process.