deisel shut off soleneoid

Karl Townsend

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Feb 14, 2010, 11:59:16 AM2/14/10

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A guy just replaced the starter solenoid on my friend's boat. The diesel
shut-off solenoid then immediately blew. Lots a smoke out of the top of the
can.

I suspect something may have gotten miswired and said I'd check in to it.

OK, this is a Cummings 6 cylinder diesel. 7 liter I think. The fuel pump
shut-off solenoid is just a mechanical 12 volt solenoid that pulls a shaft
about 0.75". But I'm puzzled, it has three wires. Anyone know how one of
these works electrically? I don't see the need for three wires.

Karl

RLM

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Feb 14, 2010, 1:21:00 PM2/14/10

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The three wire solenoids that are used on aerial equipment throttles has
one negative two positives. The two positive wires pull the solenoid in
then one positive is dropped to allow a lower amperage to hold the
solenoid in when the plunger bottoms out. The voltage is still on all
three wires but amps only flow through the holding winding. The solenoid
itself disconnects one coil inside when it bottoms out.

You have a strong pull to bottom out then it takes less power to hold.
Solenoid doesn't over heat this way.

Of course the engine returns to idle when you release the foot switch and
voltage is dropped from the throttle solenoid.

These are what I'm familiar with.

HTH

Ignoramus16496

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Feb 14, 2010, 1:31:04 PM2/14/10

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There are two coils, the high power pulling coil and a low power
holding coil. The pulling coil is needed to pull the solenoid in
position, and then it can be held by the low power holding coil.
The pulling coil usually is tired to starter, holding coil is
connected through the start/stop system.

It was probably miswired and the pulling coil was energized all the time.

I remember the name holding coil but the "pulling coil" may be called
differently officially.
i

Karl Townsend

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Feb 14, 2010, 4:01:20 PM2/14/10

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Thanks guys.

I'm almost sure both wires got put to key on. Instead of one to key on and
one to start. Makes perfect sense.

To get on the water again, I made a mechanical linkage to turn the fuel off
so we can fish till a new solenoid gets here. I'll triple check wiring
before installing.

Is there a way to know for sure which is the high power 12 volt hot and
which is the low power 12 volt hot?

Karl

"Ignoramus16496" <ignoram...@NOSPAM.16496.invalid> wrote in message
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Pete C.

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Feb 14, 2010, 4:58:15 PM2/14/10

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Karl Townsend wrote:
>
> Thanks guys.
>
> I'm almost sure both wires got put to key on. Instead of one to key on and
> one to start. Makes perfect sense.
>
> To get on the water again, I made a mechanical linkage to turn the fuel off
> so we can fish till a new solenoid gets here. I'll triple check wiring
> before installing.
>
> Is there a way to know for sure which is the high power 12 volt hot and
> which is the low power 12 volt hot?

The high current "pull in" coil should have notably lower resistance
than the low current "hold" coil.

Karl Townsend

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Feb 14, 2010, 6:04:42 PM2/14/10

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>> Is there a way to know for sure which is the high power 12 volt hot and
>> which is the low power 12 volt hot?
>
> The high current "pull in" coil should have notably lower resistance
> than the low current "hold" coil.

Sure, makes sense.

Karl

Ecnerwal

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Feb 14, 2010, 7:31:58 PM2/14/10

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In article <4b7864a2$0$77560$892e...@auth.newsreader.octanews.com>,
"Karl Townsend" <karltown...@embarqmail.com> wrote:

> To get on the water again, I made a mechanical linkage to turn the fuel off
> so we can fish till a new solenoid gets here. I'll triple check wiring
> before installing.

Owning a diesel tractor with a crapped out charging system that I start,
and then unhook the battery and take it away to charge (it is not
installed on the tractor, or needed in any way once the tractor is
running - I do without the gauges on that one, too) and also having
spent enough time (on other people's boats) out on the water to
recognize the massive suck-i-tude of having the motor crap out offshore,
I'd suggest that the mechanical linkage might well be the superior
solution. Electrical stuff on boats loves to die. Why give the gremlins
a route to shut down the engine and prevent it from restarting?

KISS works.

--
Cats, coffee, chocolate...vices to live by

Bruce L. Bergman

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Feb 15, 2010, 3:25:16 AM2/15/10

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On Sun, 14 Feb 2010 13:21:00 -0500, RLM <r...@127.0.0.1> wrote:

>The three wire solenoids that are used on aerial equipment throttles has
>one negative two positives. The two positive wires pull the solenoid in
>then one positive is dropped to allow a lower amperage to hold the
>solenoid in when the plunger bottoms out. The voltage is still on all
>three wires but amps only flow through the holding winding. The solenoid
>itself disconnects one coil inside when it bottoms out.
>
>You have a strong pull to bottom out then it takes less power to hold.
>Solenoid doesn't over heat this way.
>
>Of course the engine returns to idle when you release the foot switch and
>voltage is dropped from the throttle solenoid.
>
>These are what I'm familiar with.

The terms I'm familiar with are "Pick and Hold" - the "Pick" coil
pulls up the solenoid from full open, the "Hold" coil keeps it up and
requires much less current.

The "Pick" coil is usually rated intermittent duty, and will smoke
itself if left on too long. You usually put a set of switch contacts
in the solenoid to open the Pick coil when it's fully in, even if you
leave power on the lead.

--<< Bruce >>--