since 1940

Continental or Lycoming Aircraft Engine Sluggish start

Operator must make several attempts before the starting motor will crank the engine.

1. Low voltage to starter. The addition of 1 or 2 ohms of resistance in the circuit caused by an oxidized connector is significant. For example, in a 12 volt starter circuit drawing 40 amperes of current, the addition of 0.2 ohms of resistance drops the current to the starter to 24 amperes. This drops the operating power from 480 to 288 watts. This is a 40% loss in operating power caused by a 0.2 ohm resistance. High current, low voltage circuits are resistance sensitive. High resistance causes heat. Check the battery terminal and see if it is hot. If it is then there is too much resistance in the cable connection --clean the wire terminals.

2. Poor ground. Check condition of ground at battery box. Carefully place your hand on the connections and see if they are warm or hot. Any resistance to starter causes heat. If the connection is warm then you need to clean the connection to reduce the electrical resistance. A few milliohms of resistance can cut your power by 1/3. Bob Nuckolls of Aero Electric Connection (full text of excellent article When a Ground is a Good Ground Not? at www.aeroelectric.com) gives us this example:

 

Battery resistance	10 milliohms
Contactors resistance	4 milliohms
15' of 2 AWG wire	3.2 milliohms
Joints & wire segments	8.0 milliohms

Total resistance 25.2 milliohms

If the starter draws 200 amps from Ohms law Volts=Amps x Ohms we have a 5.04 voltage drop or just 7.46 volts at the starter. We've lost 1/3 of our power! As Bob states: "Pushing 200+ amps makes every milliohm count" . 

3. Weak battery. If the starter engages and the propeller moves and then stalls on the first compression stroke then:
A. If hot suspect bad cables or solenoids, or
B. If cold suspect a bad battery.

4. Lycoming engines - Failure of starter Bendix to engage. Clean and lubricate Bendix drive. Lubricate screw-shaft threads and ratchet with a silicone spray. Oil should never be used because oil in that location collects dust and dirt, becoming gummy which causes the Bendix to stick. Fairly common problem.

 

	EBB-131A starter Bendix used on Lycoming engines with Prestolite starters. Did you know that the Bendix drive was invented by Vincent Bendix and first used on the Chevrolet "Baby Grand" in 1914.
	Front of starter where starter Bendix engages into starter ring gear.
	Drive gears on the Bendix to the left are completely worn away. Bendix's come in several styles depending upon how many teeth are on your Lycoming engine's starter ring gear. An incorrect match can grind some teeth down. for further information see: Starter ring gear damaged Lycoming aircraft engine

5. Continental engines, slipping starter adapter. Remove for overhaul. Common problem.

Continental starter adapter and starter adapter shaft with spring installed. Used on 360, 470, and 520 series engines

 

641500 starter adapter clutch as used in the O-200 and O-300 engines O-200 engines came with two types of starter clutches. The original engine had a pull-type starter (Delco Remy) and a Delco-Remy clutch. Later engines had a key type starter  and the 641500 clutch. Back in the 1970's this clutch cost $600 and lasted about 600 hours. Continental does have s sprag repair kit available but this had limited success. We now offer rebuilt clutches at a more reasonable price

6. Poor engine-to-mount bonding. There must be an adequate ground path from the engine to the airframe. This condition causes engine control cables or lines to carry a substantial portion of the ground return starter current. This causes these components to get hot and creates a fire hazard. One customer complained that every time he started the engine the mixture control handle got hot!

7. Cold Oil.

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Disclaimer: sacskyranch.com contains abundant information relating to aircraft maintenance. The information provided  is not intended to supercede or supplement the F.A.A. approved  maintenance and/or operator’s manuals. Those F.A.A. approved manuals must be utilized when performing maintenance and/or operating aircraft.