I prefer the Bosch style pump over all the others myself. The two things I like about it is, they are basically trouble free and they advance the to 100% fuel output to the injectors upon starting so the cylinders get a big shot of fuel when you initially crank them and the glo plugs or start aid get a nice shot of fuel to pop off. They only advance to 100% for a split second but that is usually enough. Mine start right up no matter how cold they are so long as I preheat the glo plugs sufficiently. Mine are manual so I can preheat as long as I want to but usually 10 seconds (me counting 1,001, 1002 to 10 is always sufficient.
Neither of my pumps have ever been touched but I do change the fuel filters very regularly and use anti-gel (Powerservice winter blend) in the fuel as they reside in an ambient temperature barn with no electricity. and I make sure my starting battery is always up to snuff and I also change out my starting batteries every 3 years no matter what and the terminals are clean and corrosion free and so is the battery to chassis ground cable and the battery to starter relay cable.
Because my units are pure mechanical and no computer involved, I always take the starting battery out of circuit when they are parked. I use a knife switch mounted on the negative post of the starting battery and I open the circuit when they are parked and close it prior to starting them. Finally, I use the largest starting battery with the most CCA that will fit in the battery tray, in my case a Group 31 with 1200 CCA, always sourced from a retailer that has a good turnover in flooded cell batteries, in my case, the local heavy truck dealership.
They both have block heaters that have never been plugged in. Don't need them. Sure they bang and rattle bit on a cold below freezing start but they always start and I'll let them base idle for a minute or two and then advance the throttle slightly and go in the house and have a warm cup of cocoa or coffee and allow them to warm up. I never move either until the temperature gauge has moved off the cold peg.
Just how I do it. To me, the most important aspect is a fully charged starting battery and clean corrosion free connections. People tend to ignore the starting battery and then it won't start because the battery is old and sulfated or the connections are all corroded and when you impede the flow of electrons or they are insufficient, it ain't gonna start.
Popular misconception is that batteries fail in the cold weather. Not true. Batteries actually fail in hot weather but the appear to fail in the cold, because the battery cannot deliver the cranking amps necessary to spin a cold engine and thick oil over. Batteries are pretty immune to the cold. Not so the heat and certainly not when the connections are corroded and have high resistance to electron flow.