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From: Jim Healy (no email)
Date: Sun May 18 2008 - 09:40:43 EDT
Bob Siegel wrote:
"Occasionally depressing engine-stop button fails to stop engine. It slows
but resumes running when button released."
Bob, this *may well be* "normal operation." Before you play with the
solenoid, make sure you understand the wiring of the DC circuit that powers
the fuel solenoid.
On my boat, the flybridge switch is a normally closed (n/c) pushbutton type
switch in series with the solenoid. The solenoid is powered on whenever the
key switch is turned "on." Pushing the "Stop" button drops the solenoid and
shuts off the fuel supply. However, since the key switch is still in the
"on" position, releasing the "Stop" pushbutton restores power to the
solenoid. If the engine still has sufficient rpm, it will restart. This
behavior is "OK" with me; I just have to hold the button depressed until I
know the engine is fully stopped.
If you don't like this behavior, you need to add a relay lockout circuit
that will not allow power to be restored to the solenoid when the "Stop"
bushbutton is released. If you're knowledgeable of electrical control
circuits, this is easy to do. You'll need a relay with two independent
normally open (n/o) contacts. Use the "Start Key" start signal to pick the
relay coil. Use one of it's n/o contacts to hold the coil up. A second n/o
contact electrically replaces the existing pushbutton. In this arrangement,
the "Stop" pushbutton would be wired into the relay coil hold circuit. When
the "Stop" button is not depressed (it's normal state), the relay coil is
energized upon engine start and holds itself up when the start signal goes
away. When the "Stop" pushbutton is depressed, it drops the relay, removing
power from the solenoid. This effectively kills the engine. And, since the
relay coil needs a start signal to pick the relay, the now deenergized relay
prevents the solenoid from reenergizing when the "Stop" button is released,
and the engine does not restart regardless of how quickly the "Stop" button
is released.
If you do this, make sure you use marine grade materials.
Peg and Jim Healy aboard Sanctuary,
currently at Hayes, VA
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