I have a 1983 RHD BJ42 from Australia. I've had it about 14 years, and every few years when it becomes difficult to start when it's getting down into the 30 degree range, the rest of the time no problem. I pull the blow plug and usually 3 out of four have the tips burned off and the wire glow element is showing. In warmer weather I guess the one working glow plug is enough to get it started and the other cylinders kick in when the engine is starting. I was told by one of the techs at Specter Off Road when I was buying a new set of glow plugs, and he saw that I'd bought a set before, that this isn't normal. If that's true, what is causing it, and most importantly, what can I do to fix the issue?