Starting a Variable Compression Diesel

Quoting Roger Schroeder, who is quoting Ken Croft:

Ken told me how to start a diesel. He said, "fill the tank, open the needle valve turn, draw some fuel into the fuel line, prime through the exhaust port, blow into the exhaust to remove excess fuel, flip the propeller while slowly increasing the compression. When the engine fires, increase the compression to get continuous running. If the engine is too lean and dies, open the needle valve another turn and repeat. Do this until extended running is obtained."

The idea is that a diesel engine will run only a dozen or so revolutions on a prime. The fuel must be in the fuel line and the needle valve opening somewhere about right to sustain running.

Ken added, "Once it is running, increase compression until there is smooth running, but do not over compress. The engine will stop. Better a little under compressed, than over. Also, close the needle valve for best running. A point of closing will be reached where the engine suddenly quits. Back up about turn and that is the run setting."

Couldn't have said it better myself. Starting diesels is an technique that requires more "feel" than a glow. With practice, you'll learn when to back off the comp, when to screw it down, etc. Compression setting and needle setting are linked too. To make the engine run slow, back off the comp, but as this decreases the pumping action, you'll need to open the needle usually, or it will die. Once it's running happily though, just stand behind it and drink in the wonderful smell!



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