Diesel Engine Cold Start in a School Bus

This diesel engine in this video started up quite nicely compared to other buses I’ve encountered during winter conditions. The batteries were in good shape and there were no mechanical issues with the fuel system. So what could cause a poor start on a diesel engine?

First thing is block heaters or diesel coolant heaters. Are they working properly which would be obvious if the engine turned over like a slug and died. The block temperature is important with engine oil being thicker than normal which is measured by a term we call viscosity ….the resistance to flow.

If the oil flows like molasses you’re in for trouble. I remember (here we go with a “way back when story”) using ducting with a propane torch pointed at the oil pan to heat up the engine oil to assist start up. How cold was it? -25 even -30 before the winter temperatures changed drastically (global warming?) over the last several years.

Winters in my part of the country (20 yrs ago) were guaranteed to present very chilly conditions and really it was a nice dry cold that you got used to. But when it came to starting up a frozen diesel engine out came the old furnace ducting and propane torch…even used good old ether as long as you took it easy on the amount you used. Yes it was tough back then but you had to get used to it. Times have changed, we are in to a warmer climate more often than not so it’s rare to have a cold snap.

So here are a few tips if you do get a run of cold weather and have diesel engines to maintain. Like I mentioned make sure the block heater is working and the plug in has not blown the breaker. Most block heaters draw around 7 amps so a 15 amp breaker will do. Use a lighter engine oil so it flows easier in the cold. There are good synthetic blend oils that come in a 0w30 or 0w40. The zero means a very little resistance to flow.

You want that oil to flow through out the engine as soon as possible to lubricate all the moving parts and get to the turbocharger before it builds RPMs. Batteries have to be in good shape so test them before winter. Any doubt change them out it’s well worth the cost when you’re in a pinch in the dead of winter. If you can afford a diesel coolant heater they really help get the block semi warm…. enough to make a huge difference when the temperature drops. We use ‘Proheat’ heaters because they work well and are very reliable.

Pray your starter will come through when it’s under a heavy load. The torque demand is huge on a starter in -20 weather. With all that said these checks aren’t hard to do but have to be done in order to keep the wheels turning.