Fundamental principles.
Diesels don't have problems "cold starting" because of cold air, but because of cold steel.
Cold air is denser than hot air, cold air gets literally more air per stroke into a cylinder, and thus, more air to burn more fuel in, and so more ultimate power, if turbo diesel intercoolers could cool to below freezing they would boost power significantly.
Like cold air, cold steel in denser than warm steel, because it contracts, because this expansion and contraction is fairly linear per degree of temperature, an object B twice as long as object A will expand or contract twice as much, so barrels and pistons are different sizes, like A and B so expand or contract a different amount, so the gap between them increases or decreases, thus raising or lowering compression.
This gets worse if you use dissimilar metals, and alloy piston instead of a cast one means a bigger gap when cold, lower still compression.
Heating the intake air doesn't do anything to fix this, except eventually over time, it will carry some heat into the cylinder.
Cranking generates heat of compression, which heats up the cylinder far more rapidly.
An in-cylinder glow plug creates a hot spot, desireable on a cold engine, to ease starting, by making a source of excess free electrons to propogate a flame front, a hot spot on a hot engine is a bad thing BTW.
Heating intake air will, slightly, excite the air molecules and do the same thing as the in cylinder glow plug, but far far less efficiently.
Cold oil is more viscous too.
Genuine Lister CS did everything right, the bitch will start as long as the diesel will flow, go away from that in a clone and every deviation makes things harder, the way to fix that is make things more like the original, not less.
Those living in real cold places have always had the solution to the problem of starting with cold steel, they heat the steel, pretty much directly, by heating the water jacket, smaller engines used block heaters and big engines used small donkey engines plumbed into the same water/coolant circuit, a 1kW electric immersion heater plumbed into the lowest point of a lister coolant circuit (with thermosyphon, no thermostat to screw things up) will heat even the coldest listeroid enough to start.
You don't need a water pump, this is not a car engine shoehorned into an awkward space, nothing in this world stops you having a coolant circuit with enough height from top to bottom to ensure thermosiphon, and thermosiphon can only not work when your coolant has leaked out.
May I remind you that hurricanes are proof that thermosiphon scales to multi gigawatt sizes, and never ever stops working, the laws of physics insist that temperature differential = flow....
"will it start cold" was always the benchmark for buying a diesel powered anything, if it started from cold there wasn't a lot wrong with it, if it didn't then walk away and buy another one, not because it couldn't be fixed, but because you don't buy ANYTHING from people who could not be bothered to maintain their kit.
If your diesel will not start cold, fix it, don't bodge it, and fixing it means addressing the issues of cold steel dimensions vs hot steel dimensions, not bolting on heath robinson gimmicks.
"fix it" in a single cylinder stationary engine is nothing like "fix it" in a cummins 6 installed under the hood of a pickup truck, which can be an awkward, time consuming, expensive pain in the ass, in a lister it just means worst case rebore + piston + rings and a head job, which will be both quicker and cheaper than all these fucking around bodges and gimmicks. Notably, it will be orders of magnitude more reliable, and also pay back big dividends elsewhere, eg fuel economy, emissions, noise, smoothness, reliability, ability to pull a sustained load.
