Why is Why Engine Blow Out not condoned by Electro-Motive?

Both the SD70MAC Operator's Manual (CSX Transportation - Road Numbers 700 thru 724), and the SD80MAC Operator's Manual (Conrail Quality - Road Numbers 4100 thru 4127) have a NOTE using the same words about Engine Blow Out: "While this practice is extremely detrimental to starting motor service life, it is possible, but not recommended to do this . . . . ."

It seems to me that if the cylinder test valves are open when cranking the engine, as is the case for engine blow out, the peak torque requirement for the starting motors would be much less than required for the routine engine purge cycle, and therefore less (?) detrimental to service life. What am I missing?

Do these newer locomotives have auto-start (which includes cylinder purging) ?

Yes, I believe so.

Then that sounds like a plausible explanation :

If the autostart process already blows the cylinders, then so doing so manually is duplicate effort (and wear/tear) ...

- litz

litz wrote:Then that sounds like a plausible explanation :

If the autostart process already blows the cylinders, then so doing so manually is duplicate effort (and wear/tear) ...

- litz

From what I read, the desired engine starting setup procedure (prior to actual start) includes putting the fuel injection switch in the STOP position, opening the cylinder test valves and then barring over the engine at least one revolution to check for leakage from the open test valves. Then the cylinder test valves are closed and the fuel injection switch is returned to RUN position.
The above is supposed to be done before the actual engine starting procedure which includes the purge cycle (with the cylinder test valves closed) that limits the cranking speed to 30 rpm until the engine has made 1.67 revolutions.
It doesn't look like duplicate effort to me.

Ahh, gotcha.

butts260 wrote:

litz wrote:Then that sounds like a plausible explanation :

If the autostart process already blows the cylinders, then so doing so manually is duplicate effort (and wear/tear) ...

- litz

From what I read, the desired engine starting setup procedure (prior to actual start) includes putting the fuel injection switch in the STOP position, opening the cylinder test valves and then barring over the engine at least one revolution to check for leakage from the open test valves. Then the cylinder test valves are closed and the fuel injection switch is returned to RUN position.
The above is supposed to be done before the actual engine starting procedure which includes the purge cycle (with the cylinder test valves closed) that limits the cranking speed to 30 rpm until the engine has made 1.67 revolutions.
It doesn't look like duplicate effort to me.

The Loco's we use at work are the EDI/EMD GT46ace aka LDP class , an export version of an SD70ace with Teir 2 and EFI and when shutting the engine down when not in Autostart sequence it states that the EFI switch must be switched in "off" position after shutting down and when baring-over of the engine,and must only be done by maintanence staff at EDI/EMD as it will basically void the lease agreement and that the locomotives em2000 computers initiate EMD's later version of "Creepy-Crank" to auto purge and avoid hydraulic lock and it can not be isolated by the PB11 module as on on earlier EMD dash-2 models.

I know this is a little off the subject but when we had our JT26C-2SS loco.s aka the 81 class they were not fitted with a Turbo lube pump timer that will engage for 35 mins after shutting down the engine so the engineers would get paid in the early eighties to "baby sit" them for 2 hours in idle to make sure the turbo would be
sufficiently cooled after shuting down!( though I heard there was always a pub not far from the railway wink-wink)