The installation of a solenoid to the glow plug circuit will reduce the time to hold the key or push button that powers the glow plugs preheating the engine before starting. Shorter, larger wires-more power! Details below list what needs to be done to shorten the long trip from the battery, to the engine instrument panel, then back to the glow plugs. The long run is a killer in depleting amps, so it takes more time to heat up the plugs, (over 30 sec.). With the solenoid installed, the switch is now on for only 10 to 15 seconds.
Solenoid, 12v, O.E.M. Quality Solenoid Ford Starter Solenoid SW3 STD # SS581, Niehoff #FF143A or Wells #F-496 approx. $9.00 or better yet a marine grade West Marine solenoid for $19.95
Six feet of #8 wire
Three large stud round wire connectors (#8) for starter (1) and solenoid studs (2)
One small stud round wire connectors (#8) glow plug
Grounding wire, two feet #14 wire with end connectors
1: Mount solenoid with its mounting flange tabs. Most solenoids have two tabs with holes for mounting. These tabs must be grounded for the solenoid to work. Fabricate a plate or find close to matching bolts on the rear of the engine. This was not possible on my M25 so I mounted mine UNDER the fiberglass/wood lip that the engine hatch rests on above and rear of the engine. This means that it is hanging upside down over the rear of the engine. Two bolts were used to mount it, using one of the bolts to connect the ground wire that is wired to the ground on the engine. If you have a M25XP engine, you can mount the solenoid through the bolts that hold the heat exchanger in place.
2: Remove white (I think it's white) wire from last glow plug. This is the wire that goes up the wire harness to the glow plug switch. DO NOT cut the end off the wire to make it shorter. If you ever have a problem with the solenoid, then you can always connect it back to its original wiring. Connect this white wire to the small stud on the solenoid. Some solenoids have two small studs. One is not used. Before installing, ground the solenoid and touch a hot wire to the small studs one at a time. One of them will make the solenoid "CLICK". That is the one you connect the white wire to.
3: Connect the (+) side of the starter to one large stud on the solenoid. Use the #8 wire, cut to size with the end connectors crimped or soldered in place.
4: Connect the other large stud on the solenoid to the glow plug where the white wire was removed. Use the #8 wire, cut to size with the end connectors crimped or soldered in place, one large and one small connector.
5: Go to engine panel, turn on key and push the glow plug switch and you should hear a click of the solenoid down by the engine. Hold for 25 sec, shut key off and return to engine and see if you can burn your finger on the top of a glow plug. It still should feel hot. I now hold the push button for only 12 sec instead of 25 to start the engine.
Comments: The engine panel is fused, so the control of the solenoid is but the (+) from the starter through the solenoid to plugs is not. This is a problem if the solenoid should malfunction and remain "HOT". You will burn out your glow plugs because you will not notice they are on. I have never heard of this happening but I have a safety light that I have added for this. Another way to determine if the glow plugs are working is to watch the voltmeter when you push the glow plug "ON". The volt should drop (1+) volt and when the button is released the voltage should rise back to normal.
Safety Light: Purchase a 12v low amp auto 1/4 inch dash light that you mounted in the engine control panel. Ground one side of the light at the panel and run a #14 or #18 wire down to the top of a glow plug or that side of the solenoid. When you hold the glow plug push switch on the glow plugs and the dash light will both be on. Release the button and they both go off.
Al and Michele #55 "Kindred Spirit"
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