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Cox Engine Troubleshooting Guide
  1. The engine starts but only runs for a short burst, producing a powerful high-speed "BRAAAP!" sound, then quits.
    The probable reason is that the needle valve setting is too lean (the engine is not getting enough fuel ). First, completely close (turn clockwise) the needle valve finger tight. Then open (turn counter clockwise) a full 4 turns. Prime the engine and try again. If the problem persists, open the needle valve (counter-clockwise) another 1/4 - 1/2 turn, re-prime the engine and try again. Also, check to make sure you have filled the fuel tank and check the glow head for proper operation.
  2. The engine starts but only runs for a short burst then quits, and a lot of excess fuel is coming from the exhaust port.
    Most likely the cause is similar to situation 1; an incorrectly set needle valve. However, this time the needle valve is set too rich, (the engine is getting too much fuel). In this case you want to close (turn clockwise) the needle valve approximately 1/2 turn. DO NOT prime the engine. Since there is already too much fuel, adding more fuel will flood the engine. Connect your glow plug clip and attempt to start the engine again. This may require several attempts before the engine starts. If the problem continues, close the needle valve another 1/4-1/2 turn and try again. If this procedure fails to provide you with a successful start, disconnect the glow clip and then close the needle valve all the way until it just begins to tighten. Then open the needle valve 4 full turns and attempt to start. As before, do not prime the engine. If the engine still fails to start, check the glow head for proper operation.
  3. The engine starts but will not run smoothly.
    Again, like the previous situations, the needle valve setting is probably incorrect. Continue to adjust the needle in (leaner) a little at a time (1/8 - 1/4 turn) out until engine runs smoothly.
  4. Bubbles appear under the glow head and the engine will not run smoothly.
    Check the tightness of the glow plug head using a head wrench. A loose glow head can lead to erratic engine performance.
  5. If your engine will not fire or run at all, the probable reasons are:
    a) Your starter battery may be weak or dead. Recharge or replace.
    b) Bad connections of glow head clip wires to the battery terminals. Check to be sure glow clip is firmly and correctly attached to glow head. Reconnect wires to battery. Reattach glow plug clip.
    c) The glow head has burned out. Replace with a new one.
    d) Engine is not primed or has lost prime. Reprime engine.
    e) Engine is flooded (needle valve open too much). Go to #6.
    f) Loose flywheel. Tighten flywheel.
    g) Out of fuel - refill fuel tank.
  6. If your engine is flooded (too much fuel in cylinder).
    Indications of a flooded engine is a hard-to-turn (or stiff) flywheel or one that "kicks" when winding clockwise to start. Fix by closing the needle valve completely and continue to start the engine (with glow head clip attached) until a short starting "burst" occurs. Stop and open needle valve 4 turns, prime, and start again. Caution: Always disconnect glow head clip from glow head when priming engine.

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