Engine Starting Problem & Glo Plug Solenoid

[britinusa]

And.... I'm pretty sure the glowplug solenoid mod is NOT installed.

As far as I can see, the electrical wire from the aft end of the glow plug line runs around the back of the engine, across to port where it's wrapped in a curly earth wire that is connected to somewhere on the engine (out of sight, but below the back of the expansion tank) then the glow wire disappears into the harness that goes up to a chocolate block type connection that is inside an inverted plastic box screwed to the underside of the engine wood work. There is no sign of the glow wire going to a solenoid.

I'm curious about the reason for the solenoid mod. Is it's purpose to avoid having the total glow plug current flowing through the glow plug switch? (and possible switch resistance affecting the current going to the glow plugs) ???

Paul

[Noah]

Paul: Lots written on this:
http://c34.org/bbs/index.php/topic,8084.msg56366.html#msg56366

http://c34.org/bbs/index.php/topic,8265.msg58008.html#msg58008

[Ron Hill]

Paul : The reason for the glow plug mod is simple. 
Originally the factory wired the glow plug current to go from the battery connection on the engine, all the way back to the glow plug switch on the engine panel, and then back to the glow plugs!!

The mod takes the current from the battery engine connection to a solenoid then to the glow plugs.  The solenoid is "opened ON/closed OFF"  by the glow plug switch on the engine panel.   

Clear as mud?  A thought

[britinusa]

Thanks Ron.

Paul : The reason for the glow plug mod is simple. 
Originally the factory wired the glow plug current to go from the battery connection on the engine, all the way back to the glow plug switch on the engine panel, and then back to the glow plugs!!

That's pretty much what I expected.

The mod takes the current from the battery engine connection to a solenoid then to the glow plugs.  The solenoid is "opened ON/closed OFF"  by the glow plug switch on the engine panel.   

Clear as mud?  A thought

You said it ' Clear as mud'
Surely the solenoid should be open (when the switch is open) or closed(when the switch is closed) ie. Opened/Off Closed/On



Paul

[Stu Jackson]

You said it ' Clear as mud'
Surely the solenoid should be open (when the switch is open) or closed(when the switch is closed) ie. Opened/Off Closed/On



Paul

This is THE glow plug resource:  http://www.c34.org/wiki/index.php?title=Faster%2C_More_Efficient_Glow_Plug_Heating_with_a_Solenoid

The glow plug button, when depressed, closes the solenoid.  When the button is released it opens the solenoid.

[KWKloeber]

solenoid

Paul note that everyone keeps using the term glow plug solenoid.  There's no reason (JTSO) to use a piece of equipment that is meant to switch 300 amps, for a 18-amp load.   There's benefits to using a simple, available-everywhere relay, vs. a ford-type starter solenoid.

However there's drawbacks to doing the mod in the first place (cost, adds another failure point, needs another fuse, potential damage to glow plugs.)  The benefit is it reduces how many seconds one's finger is on the preheat button.  Weigh the pros/cons.

kk

[Lance Jones]

I understand what you are saying KK that the potential for 300 amps is there. However, how will it generate 300amps? Is that available in our electrical system?

One of my biggest reasons for doing my modification is for safety. I either have been in, or have seen others is situations where a few seconds difference in starting an engine could mean the difference in being washed onto a lee shore or being rammed by some other vessel.

[KWKloeber]

the potential for 300 amps is there. However, how will it generate 300amps?

One of my biggest reasons for doing my modification is for safety. I either have been in, or have seen others is situations where a few seconds difference in starting an engine could mean the difference in being washed onto a lee shore or being rammed

Apparently I  missed my intended mark.  I didn't mean the potential for 300 amps is anywhere.  I'm saying the starter solenoid (with it's huge capacity) is overkill and a more expensive option than a $10 relay (capacity 40 amps.)  You don't buy a front loader to move a shovelfull of soil -- you can do it it with a shovel. 

And the relay is simpler, more available, cheap to carry a spare, more quickly swapped out (plug and play wire harness socket,) etc.  Oftentimes we sailors choose a more difficult solution, when the simplest one meets the same end.

As to whether to do the mod or not, YBYC -- I wouldn't suggest a sailor not do it if s/he decides to.  What I said was "Weigh the pros/cons." -- i.e. YBYC.   An alternate approach might be, ignore the cons and just do it.  One of the pros I forgot to mention was longer preheat switch life (not pumping 18 amps thru it.)

I can formulate scenarios where using a relay is "better" than using a starter solenoid.   And the same for when OEM (same lee shore condition) would be better than doing the mod at all.  e.g., one of the additional failure points kicking in - the additional fuse blew, fuse and terminal connections are corroded, slave relay/solenoid has failed -- or unknowingly burned out a 10-volt glow plug with the 14+ full volts.  Or the guest crew member sensed the danger and so has been holding the preheat on for a minute to help you out just in case.    Due to Murphy's Law kicking in, in that event I'd rather have the simpler system. 

JTSO. 

If we approach any situation where 10 seconds may mean life or death, a safer approach might be to start the engine and let it idle just in case.  I've put ego aside and done that many times.

The mod has become accepted because it's been around so long -- but I suspect that the 1st-ever mod was not totally thought thru to the final result (no doubt thought that the glow plugs should receive 14+ volts?)

Let's approach this another way --

Suppose Universal built in a circuit that limits the voltage at the plugs to their design 10 volts.  And that one of the forum came up with the idea, "Hey, I'm going to eliminate the circuit so I can shoot 14 volts at my glow plugs and save 5-10 seconds of finger time." 
How many would jump on the bandwagon with, "Hey that's a GREAT idea! Go for it.  I'm going to do that also."? 
Or would the consensus be, "I wouldn't, but YBYC."?

Again, weigh the pros/cons of the mod vs OEM. 
As to the other, I don't immediately see any benefit to the starter solenoid over a relay -- but am listening for some.

Cheers
Ken

[J_Sail]

Not to further muddy the waters, but I don't know why everyone is saying that the mod will result in the glow plugs being subjected to 14 volts (and might fail prematurely as a result). That might be the case if the engine was running and spinning the alternator, but it's not. A battery bank with an 18 amp load on it will put out on the order of 12.6 - 12.8v. The actual voltage at the glow plug will be slightly less. Even if I am off by a few-tenths of a volt, I fail to see how the glow plugs will be exposed to 14v.

Just a thought

[mark_53]

One of my biggest reasons for doing my modification is for safety. I either have been in, or have seen others is situations where a few seconds difference in starting an engine could mean the difference in being washed onto a lee shore or being rammed by some other vessel.

Lance, the solenoid mod is only of benefit when the engine is COLD. For me, that means when I arrive at my slip or wake up in the morning to start the engine. The engine stays warm for several hours after motoring to sail. What is the likelihood of being in a critical situation with a cold engine and only 5-10 seconds to spare vs. the likelihood of the solenoid circuit failing regardless of engine temperature?

[KWKloeber]

Not to further muddy the waters, but I don't know why everyone is saying that the mod will result in the glow plugs being subjected to 14 volts (and might fail prematurely as a result). That might be the case if the engine was running and spinning the alternator, but it's not. A battery bank with an 18 amp load on it will put out on the order of 12.6 - 12.8v. The actual voltage at the glow plug will be slightly less. Even if I am off by a few-tenths of a volt, I fail to see how the glow plugs will be exposed to 14v.

Has anyone with the mod ever experienced premature glow plug failure? Unless the problem has occurred, we may be worrying about something that is more theoretical than real.

Just a thought

Could you see a scenario where 14v could happen being tied to the dock and a shore charger (when it's most needed)?

Ok, say 12.8v on the reserve battery,  nearly 30% over voltage-ing the plugs -- a good idea?  Maybe a chart taped to the cockpit of finger time versus battery voltage (just to make it more difficult and add in another factor?  It is an issue - Kubota actually has a time limiter in the tractor preheat circuit (- unsure how many seconds it's set for.)

kk

[mark_53]

Not to further muddy the waters, but I don't know why everyone is saying that the mod will result in the glow plugs being subjected to 14 volts (and might fail prematurely as a result). That might be the case if the engine was running and spinning the alternator, but it's not. A battery bank with an 18 amp load on it will put out on the order of 12.6 - 12.8v. The actual voltage at the glow plug will be slightly less. Even if I am off by a few-tenths of a volt, I fail to see how the glow plugs will be exposed to 14v.

Has anyone with the mod ever experienced premature glow plug failure? Unless the problem has occurred, we may be worrying about something that is more theoretical than real.

Just a thought

J_Sail, you are probably correct, I'll leave it to others to debate the technical issues, but it does introduce more complexity for very little, if any benefit.

[britinusa]

Great responses. Surprising amount to consider.

My preference is to keep it simple.

So I'm going to hold off doing the mod and, assuming that the existing glow switch & starter switch are original, I have just ordered a spare start/glow button from CD (and the Red & Black Boots)

Thanks for the input guys.

Paul

[Stu Jackson]

J_Sail, you are probably correct, I'll leave it to others to debate the technical issues, but it does introduce more complexity for very little, if any benefit.

I've had the solenoid in since I sketched that wiring diagram, IIRC, 1999.  My plugs are just fine.

One thing I may have missed in this back and forth:  The WIRING.  The amps going up to the cockpit panel and back.  Big amps in small wires.  That's the main reason I put the solenoid  on my boat.

Heck, kids, if you can run a sailboat with its complicated rigging and stuff, one would think a skipper could count to ten and let the button out.  Our Mark I cockpits are so small, one person has an issue getting back there to push the button, a real stretch to say a crew member would do it to "help out."  Truly stretching it. 

What's been very GOOD about this thread is that it points out the advantages and (potential but I believe imagined) disadvantages of doing it.

Your boat, your choice. 

[Ron Hill]

Guys : Sorry about all the confusion. 
With the solenoid modification, when the switch on the engine instrument panel is turned ON the solenoid allow the current to pass to the glow plugs.  When the switch on the engine panel is turned OFF the flow of current thru the solenoid stops!! 

As far as any increased voltage problems goes :
1. I used # 6 marine grade wire in the new solenoid circuit in my M25XP engine
2. I usually engaged the glow plugs for 10-12 seconds
3. I installed that mod when the engine had about 1000hrs
4. When the engine was replaced (for other reasons) the original glow plugs were still installed
5. The mod was used for about 4000 hrs - that's a bunch of starts!!!!

The solenoid modification was a GREAT mod for the M25 and M25XP engine