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Adding Solenoid to Glow Plugs.

JSM

Member III
I'm in the process of installing a solenoid to speed up heat time on my glow plugs. So far I have wired up everything according to instructions on Mainsails website. As of now the solenoid clicks when the glow plug button is pushed but it seems that I am getting no power to the plugs.
I have mounted the solenoid to the engine block using one of the bolts that holds the heat exchanger bracket in place.

11-Universal-Diesel-Wiring-Harness-Upgrade-2.jpg

Do I need to ground the solenoid to the block or is mounting it to the (bare metal) heat exchanger bracket good enough ?

Thanks
JSM
 

Kenneth K

1985 32-3, Puget Sound
Blogs Author
I haven't done this upgrade yet, but I have the solenoid sitting on the boat, ready to go. If the solenoid is clicking when you press the glow plug switch, it sounds like you have a good ground on the solenoid. Check the glow plug side of the circuit with a voltmeter, light bulb, etc to verify good voltage from the starter post when the solenoid clicks.

Let us know how you like the final results.....
 
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Frank Langer

1984 Ericson 30+, Nanaimo, BC
Hi guys,
Despite my ongoing efforts to learn everything I can to upgrade and maintain our E30+, I haven't heard about this upgrade. The only solenoid on our boat is on the starter motor. Can one of you explain what this upgrade is, what it is intended to do, how necessary it is, etc. In case it's relevant, our boat is wired with a start key, a glow plug button that I can operate without having to turn on the start key, and then a separate start button. So my order of operations is 1) run the glow plug for 15 - 30 seconds, depending on outside temperature; 2) turn on the start key; 3) push the start button to start the engine. It all seems to work effectively.
Thanks for any information you can provide!
Frank
 

bigd14

Contributing Partner
Blogs Author
Hi Frank- Instead of a long run of wire carrying high voltage from the instrument panel to the glow plugs, this mod runs a small wire from the panel to the solenoid and then a short run of large wire from the starter post through the solenoid and to the glow plugs. They heat up quicker and you have less risk of overheating your small wire.

And I ran a short negative wire from the solenoid mounting bracket to the negative bus just to make sure I was getting full current flow to ground even though I mounted it on the heat exchanger bracket.
 

debonAir

Member III
Technically it's just a relay, not a solenoid, the difference being a solenoid pulls something in magnetically like the starter motor pinion gear as well as engaging the starter motor circuit, and the relay just closes a circuit.

I've read a few things about this particular upgrade. Some say that the losses of the wire going to/from the switch panel are expected in the design and that routing them with shorter/lower gauge wire could actually cause glow plug burnout.

I decided not to do this one, at least for now, because relays do fail and holding the glow plug button for 15 vs 20 seconds only when the engine is cold isn't worth all that effort.

On my engine I discovered my difficulty starting had to do with a missing governor "starter spring" and in fact the engine starts fine cold now even with 0 seconds glow plug (discovered by having a newbie start it, and it just took a bit longer). If someone's ever removed your timing gear cover and didn't know to remove that spring, which is tiny, and the only thing that connects between the cover and block besides the bolts, then your might be missing too. Symptoms are longer start times and needing to goose the throttle up a bit to start, which is what this little spring's job is apparently.
 

Tin Kicker

Sustaining Member
Moderator
This is a worthwhile change from a few technical aspects. Thanks for the idea, even if not originally your own.

1. The biggest to me is that it removes the need for a high current switch. Mine is corroded externally so I've been wanting to replace it.
A. Low current key and other switches are easy to find (keyed or keyless) and high current ones are less common and more expensive.
B. Running high current thru a switch is harder on the contact faces than on those in a relay, because the relay opens and closes so much faster, leading to less burning of the contact faces.
C. It's pretty easy to find a relay anywhere which can carry high current, because there is at least one in the starter circuit for almost all cars.

2. This change removes a big portion of the high current route, which is always desirable. Chafe a piece of metal through a small gauge wire and the wire will probably sever or the circuit breaker will trip and either is easy to fix. Chafe near fuel or other flammable vapors and there is much less chance of ignition. Chafe through a 10A to 30A circuit and you can blow a hole in the metal that the cable is rubbing on, or cut all the adjacent wires if the chafe happens in a bundle. Not easy to repair quickly and easily. It is also much easier to ignite whatever else is in the area.

3. Contamination is the #1 cause of failure for both relays and switches. Relays are incredibly robust on their own and being in the engine compartment one will be more protected with the high current circuit, rather than being in the wetter environment of a cockpit locker or pedestal.

4. If a relay were to fail, the work-around is to simply take a piece of wire and short the terminals together. (Use heavy enough wire, ventilate the compartment, wear gloves, and beware the likely flash.)
 

JSM

Member III
Thanks All. Checked things out yesterday with the volt meter and discovered that I have power going into the solenoid but no power going from the solenoid to the glow plugs when the glow plug button is pushed. Will try again with a new solenoid.
 

sharonov

Member II
.....I decided not to do this one, at least for now, because relays do fail and holding the glow plug button for 15 vs 20 seconds only when the engine is cold isn't worth all that effort.....
I am with you on this. Even though I replaced every wire, gauge and switch on my engine, I decided against this upgrade. The engine worked fine without this relay for 32 years. Just make sure to use weatherproof switches rated for a sufficient current. Of all places, shockingly, West Marine seems to be one of the better sources. For a number of reasons I replaced key switch with a toggle.
Things should be only as complicated as necessary. Simple things tend to work, complicated not so much.
 

JSM

Member III
Had time yesterday to readdress the solenoid issue and discovered that it was defective as well as over kill for the intended application (Duralast F496). Went instead with a 30amp automotive relay. Did a quick job of roughing the wiring in just to see how things would work and was pleased to discover that that the engine fired up in aprox. 10 seconds versus the normal 30 plus.
If the relay fails it can be swapped out as easily as changing a fuse. Or the grey glow plug wire can be put back in its original position.
 
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