Fusebox LM27

[lohisailor]

We have owned an LM27 for a few months only.  The Bukh DV20 is fitted with a thermostart but when operating the ignition key to the heat position there are no volts at the thermostart terminal.  The Bukh engine wiring diagram shows a 25 amp fuse protecting that circuit. We have hunted everywhere but cannot find any engine fuses.  Does anyone know where this fuse might be?

[Brian & Glenda]

I'm no Bukh engine expert, and my DV36SME has no glow plugs, but I suggest that typically a engine's thermostat and any glow plugs that would be warmed by a 'heat position' on your ignition switch, are two different things. There normally wouldn't be any electrical connection between the two.

The thermostat has no electrical wiring. It is simply has round device that sits under a housing that has a coolant hose running from it, somewhere near the top of the engine. It has a has a section that expands and contracts with changes in coolant temperature, to open and close its valve according to a preset temperature. My thermostat is designed to keep my coolant at 180 degrees Fahrenheit. There is however an electrical coolant temperature monitoring sending unit mounted near the thermostat, that monitors the engine coolant temperature and reports that temperature to the guage and perhaps an alarm on your dash.

The heat position of an ignition switch, typically sends electrical current to an engine's glow plugs, which are usually threaded into the engine cylinder block near the fuel injectors, and are basically just resistors that warm up when current is applied. A warm diesel engine starts better than a cold engine. It is likely that a 25 amp fuse would be required for the glow plugs if these exist on your engine. Perhaps your ignition switch is an aftermarket one that has a heat position, but no glow plugs. If glow plugs exist, any fuse would be somewhere along the wires that lead to the glow plugs, but is likely either near the master engine electrical power shut-off switch, or possibly behind the dash very near the ignition switch itself.

Hope that helps...
Brian.

[Sula]

Brian, I think you've misread 'thermostart' as 'thermostat'.

lohisailor, as far a I can see the cold start facility is an optional extra, or add on part, for the DV10/DV20 which is an extension of the inlet manifold (after the air filter box) the contains a 12v heated glowplug for cold starting.  So this might not be an original fitment to your LM, and the wiring could be anything a subsequent owner lashed up.

There should be both a fuse (to protect the circuit from a short), and a relay (to avoid putting the high current required for the glow plug through the ignition switch).  

It therefore seems that the fault could be (a) a failed connection somewhere in the circuit, (b) a blown fuse, (c) a failed relay, or even perhaps (d) a complete absence of any wiring to operate the glow plug (the cold start inlet may perhaps have been fitted but never wired up).

I think you will have to visually trace the wiring (if any!) from the ignition switch (terminal 17?) to the glow coil, and see what you find.  Once you know where the wiring goes, and where the fuse and relay are, you can trace where in the circuit the voltage is interrupted.

Pics from internet of the cold start fitting itself, and the relay and wiring that comes with the kit -    


Some limited info here -

forums.ybw.com/index.php?threads/glow-plug-mod-to-bukh-dv-20.222659/
  

[Brian & Glenda]

Right you are Sula ... feel free to delete my earlier post. It has little value... but I'm still thinking that's where the fuses are likely to be! I have run a few diesel engines, but never heard of a Thermostart before, and the mind didn't pause long enough to catch the second 'r' in Thermostart... just read it as thermostat. I've learned something now I've googled to find out what a thermostart even is! Very interesting! You just never know when you might learn something new!

Cheers,
Brian.