Help Me to Understand Dry Start ?

DonBaja wrote:
Let's assume the Cummins 8.3L diesel hasn't been started for a month.

When I turn it over - is it dry metal on dry metal on the main bearings and crank? Or is it possible that the main bearings are sitting in an oil bath of some sort. There are a couple of seconds between the engine firing and the oil pressure coming up. I assume that the bearings feel oil pressure before the pressure sensor does and then the signal has to travel 36 feet to the gauge. I have felt how smooth crankshafts are where they come in contact with the main bearings and I know these main bearings are relatively soft. Having said that - does your engine die a little every time it sits for a month between starts? Are there other contact points like rod bearings that suffer as much or more than the main bearings? Thanks in advance for your insights!

It's more the cylinder wall dry scuff and piston pin bore than the crankshaft main or rod bearings on an engine that is in use already (not new or just rebuilt).

Problems used to be noted with scuffed cylinder walls on rural fire dept. equipment that had set unused for a period of time, then started and run aggressively. That type of application, that sets like an RV.

The good news is, way better oil, more knowledge of piston skirt profiles, Graphal (phosphate) coatings on piston skirts and pin bores, and incredibly good tolerances have minimized the damage from cold starts .

As far as prelubers, that would be a great idea if it could be done economically.

GM has a LS series preluber for the dealership to use if replacing or rebuilding an engine in a customer's vehicle.

My advice is, don't load the engine for a bit after starting.