Help Me to Understand Dry Start ?

[DonBaja]

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!

[Thom82]

There is plenty of lube left for the small load that is on the bearings at start-up and idle. Most manufacturers suggest not putting a heavy load on the engine immediately.

[booty51]

Ok this is an observation , and may not apply to anything here. I have a boat with electrical gauges, I didn't like the oil pressure readings at times so, I installed a mechanical gauge as well. I did notice with the mechanical gauge , as soon as I turned the key and the engine turns over the oil pump is pumping oil. I would see the mechanical gauge pulsing and the pressure increasing before the engine starts. even after long sitting periods there is a film of oil on parts providiing just enough lubrication until oil pressure builds.

All you guys doing oil analysis wouldn't this kind of wear show up?

[khogle2]

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.

[timmac]

If your worried about dry starts than use this product, it works...

http://www.lucasoil.com/products/display_products.sd?iid=25&catid=7&loc=show&headTitle= - Lucas Heav...

[Dale_Traveling]

During my Navy time I had to learn the ins and outs of the engineering plant which included the prestart procedures for the gas turbine propulsion engines, reduction gears and diesel generators. Both had prestart lube pumps with oil preheaters and coolers. I suspect the design included these system considering overhauling or repairs due to worn bearings was a major undertaking.

All consumer rated internal combustions engines from lawn mowers to the big diesels in a RV do wear very, very slightly each time they are started but even without the pre-lube capabilities the engines, most of the time, out last what ever they are bolted to. Also modern metallurgy have made vast improvements in metals used in engines extending the life far beyond what our fathers had. Local car dealer's advertisement - "200,000 is the new 100,000" is very true today.

[wolfe10]

wa8yxm wrote:
Regarding warm up time... Of course I drive a gasser. but.. on my rig you start the engine before operating the jacks.. By the tine I up-jacks, release brake and get seat belt buckled.. I'm ready to pull off the site. From there to the "Gate" is usually 5-15 MPH speed limit.. and by the time I am out the gate, engine is ready to HAUL. For a Diesel... Same times apply.

Starting and letting it idle next to me for 30-90 minutes before you pull off site... Bad for the engine. Bad for neighbor relations too.

Completely true-- and applies to ALL brands of modern diesel engines (20 years or newer).

As you suggest, both Caterpillar and Cummins recommend minimal warm up IF you will be using light throttle (i.e. within park, city streets, etc).

Sure, if you are parked at a freeway entrance, warm up (at high idle) until your coolant almost reaches operating temperature. But, at least for us, this condition is rare.

Basically if you can operate at low boost in lower gears, as soon as air pressure is built it is better for the engine (quicker engine warmup)to start driving.

[wa8yxm]

Regarding warm up time... Of course I drive a gasser. but.. on my rig you start the engine before operating the jacks.. By the tine I up-jacks, release brake and get seat belt buckled.. I'm ready to pull off the site. From there to the "Gate" is usually 5-15 MPH speed limit.. and by the time I am out the gate, engine is ready to HAUL. For a Diesel... Same times apply.

Starting and letting it idle next to me for 30-90 minutes before you pull off site... Bad for the engine. Bad for neighbor relations too.

[Gonzo42]

IMHO, modern multi-viscosity oils eliminate the worry, because there is sufficient oil on the bearing surfaces to last for a very long time. On the issue of 'warm-up time' one whole minute is completely sufficient in normal cases to get oil moving within the galleries and bearing surfaces.

One should then drive at very moderate speeds until engine reaches operating temperature.

[mpierce]

If you want to pre pressurize the oil, take the wire off the fuel valve! that way, when you crank it, it will not flow fuel. Crank for 10 seconds, stop, and put the wire back on. Now the fuel valve will allow fuel to flow, and it will start.

[wolfe10]

While I am sure pre-lubing would be a positive from a theoretical standpoint, I have yet to hear of a diesel engine failing because of an oil-related/dry start issue.

Said another way, you are trying to solve a non-problem.

[garry1p]

Farm equipment lasts for many many years and they do not have a pre lube set all winter and fire it up in the spring.

[hammer21661]

we start boat motors that have sat for years then put them to work.No problems from "dry start".All of them set for 6 months a year.

[azrving]

wa8yxm wrote:
This does not address the O/P's question but I have a thought......

Why can they not put an "oil Priming Pump" on the engine, a small electric you run for like 30-60 sedonds to "Prime" the oil system and get oil up to the top rail?

I guess the engine makers do not feel it is needed.

Years ago I remember seeing pre lube systems. It uses an accumulator to hold oil and when electrically activated the accumulator pushes the oil charge into the oil system. This one example and it comes in pre and post shut down.
http://engineprelube.com/

[jeffo]

Anyone running MotorKote friction fighter? Heard the adds. But does it really work?