Perkins pre-heaters are not always installed, but when they are, they squirts a little fuel in a depression in the air intake tract, then light it on fire, thereby pre-heating the air entering the combustion chamber.* Look to see if there is a glow-plug screwed into the intake manifold right where the air enters at the intake screen.* Should you not have one, they are available, and easy to install.* To use, hold down the pre-heat button until the puddled fuel catches fire, then begin cranking. Be advised though that it's rather scary seeing flames coming out of the intake the first time you use it. Make sure nothing flammable is near the intake.
If your engines are in good tune, your batteries fully charged, and the battery cables in good shape (very little voltage drop allowing proper cranking speed) she should start right up.* Starting problems may indicate low compression, slow cranking speeds, injectors needing service, valves out of adjustment, or simply very cold engine temps.* If you have a switch to parallel the start batteries, connecting the two together may help if she is reluctant to start....................Arctic Traveller