Mikuni MX40 Heaters
(Revised 31st March 2008)
Problems: Blowing fuses Eating battery power Blown glow plugs.
These problems above are often related to the Glow Plug / Glow Plug Boss Assembly (Chamber).
Do the following:
:
Isolate the system and remove the two cables connected to the top of the glow plug ensuring that you note all positions. It is very, very important that all washers and cables are re-assembled in the correct order. The positive wire (blue on my system), fits on the top. Underneath is an insulating washer and under that is where the white wire (negative) is fitted.
Unscrew and remove the Glow-Plug. You can easily see if it is blown. If it is not then clean it thoroughly using a non-metallic instrument (toothpick perhaps) to remove debris between the coils etc.
Carefully undo the fuel connection to the Glow Plug Boss Assembly (where the Glow Plug fits into). One should normally use two spanners for this to avoid twisting/damaging the pipe/connection. Remove the two crosshead screws on top of the chamber. Pull the chamber out of its housing turning anti-clockwise at the same time. Take care of the fibre washer and washer fitted underneath the flange.
Inspect the chamber. The inner surface is covered with fine mesh gauze that can become unstuck and lift at the edge. If the edge has lifted it may be very close to or even touching the glow-plug thus leading to short-circuiting or arcing, thus seriously degrading the system. In this event the chamber must be replaced.
If the chamber appears to be ok, clean it. There is a small hole just under the flange leading from the chamber. This must be clear.
Mikuni state that their heaters should be serviced at intervals of no longer than 12 months. If you are using Red Diesel then this is a must. What happens is that the glow-plug and ignition chamber get clogged up with the inevitable consequence of system failure. In fact, the service concentrates almost entirely on cleaning and inspecting these components.
To help reduce breakdown incidence consider the following:
Service the unit at least once a year
Do not start the engine or switch 12 volt power supplies whilst the unit is in operation
Do not disconnect power to the unit whilst the unit is in operation.
Parts: Glow Plug Product Code: 061121
Glow Plug Boss Assembly Product Code: 548014A (Recent models do not have a nut simply a nipple for a flexible hose fitting)
Fiber Washer Product Code: 12058
Parts and information from: http://www.mikuniheating.com/