Earthing Solenoid on a LPWS4

[SiFi]

Any idea what it is does?

It's in the handbook circuit diagram. I have a 70A relay wired much the same on my engine.  The earthing stud on the starter is earthed to the engine via the relay. The relay is switched OPEN when the glow plugs are energised.

Thanks

[cobbadog]

Not very well worded, but you say your wiring is "wired much the same". I feel that it should be wired exactly the same, not almost the same. Earths can sometimes also be connected to the bolt that holds the starter to the engine, not sure where your one is. Maybe a picture would help speed up some more responses.
Pictures will need to be compressed to load onto the Forum.

[SiFi]

Why would the earth on the starter be earthed via a 70A relay to the engine casing? The relay opens when the glow plugs are energised.  There is something called an "earthing solenoid" in the handbook circuit diagram that is connected the same.

[ThomasEriksen]

I agree that picture would help, even that of circuit diagram…

[cobbadog]

I cannot answer your legitimate question but need to understand the system better to be able to help.
If you are certain that the solenoid in your harness is the correct one and wired correctly then someone far smarter than me designed it, but I have not seen a solenoid on an earth before on anything I play with.
So if you are able a clear picture is worth a thousand words of the diagram so that we may be able to understand it better or the harness.

[SiFi]

Thanks for your replies.

Here is a screenshot of the circuit diagram, on the left item 4 is described as 'earthing solenoid' (relay) and item 11 in the centre is the 'glow plug controller' (relay). The photo shows the relay socket on the left with the dark greenish cables, one going to starter -ve and the other to engine casing.

I want to recheck that the earthing relay is opened when the glow plugs are energised.

[SiFi]

... circuit diagram

[ThomasEriksen]

Looks like the earthing solenoid is there to disconnect battery negative from engine for protection against galvanic corrosion since this a marine version.Also relay 11 controls both glowplug relay and earthing solenoid

[Diesel Engineering]

That is quite right. This is a marine version. The earth solenoid will close and put a feed onto the engine to allow the starter motor and glow plugs to operate. As soon as the engine is up and running the earth is removed from the engine casing. As previously said this is to try and reduce corrosion,  and also helps to reduce electrical  interference that could cause issues with various instruments. )

[cobbadog]

Glad you blokes sorted it out especially after that little bit extra information, it was a marine application.

[SiFi]

Thank you everyone for your help. It is a marine engine in a narrowboat.  In the name of simplicity I wonder whether an earthing strap would be better.

[cobbadog]

An earthing strap certainly will not do any harm and only improve that side of the circuitry plus it is a cheap addition.