Field Marshalls are full diesel unlike all the Lanz patent hot bulb semi diesel. By full diesel I mean it's a high pressure, timed injection just like any normal diesel. The Lanz hot bulb is not timed injection, instead it injects much earlier in the compression stroke at lower pressure and uses the residual heat in a cast iron bowl to aid combustion. Marshall copied Lanz, but converted the engine to full diesel. I've played with both, I find the hot bulb engine easier to start but it does take longer.
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