In a message dated 4/18/01 11:22:41 AM Central Standard Time,
kbernste@us.ibm.com writes:
<< A stranger (jealous one, I think) warned me while I was
fueling up the other day that I only had a very limited number of starts I
should
expect out of a deuce's starter, and that I should let it run
all day rather than shut it off if I'm starting up later.
Clearly there is a lifetime associated with any
electric device, but critically low enough to worry about this?
I suspect the old geez just wanted a little authority,
but I've never heard this before - comments?
>>
More than one of the many TM's I have around here say that the truck
shouldn't be shut off for short breaks (I seem to remember the definition of
short as about an hour), but rather should be left running.
I doubt it has anything to do with the starter motor. My list of suspects
for this reasoning are:
1 Turbo bearings. It is important that an adequate cool-down period be
allowed for these. Very hard on them to just pull up and shut engine down.
The oil just cooks them.
2 relationship between engine operating temperature and horsepower available.
Cold engine in loaded truck equals poor acceleration/grade capacity.
3 tendency of engine temp to rise, immediately after shut down.
4 delay restarting travel to (possibly) allow air pressure to build back up
(depending on length of stop and condition of vehicle air system)
The engine at idle burns relatively little fuel. I can't immediately lay my
hand on the exact number. But a LDT-465 at rated power & speed (130 hp @
2600 rpm) has a maximum fuel consumption of 64 lb per hour. (Source TM
9-2815-210-34)
At idle the injection pump is delivering a little less than half as much fuel
at it idle as it does at fuel load (Source TM 9-2910-226-34).
I don't know the density of diesel fuel, I'm guessing about 8 lbs per gallon,
which means at idle the truck would burn about 4 gallons per hour. I would
imagine the federal government buys diesel in the 30 cent per gallon price
range (remember, no taxes for them, plus LARGE volume discount). So it costs
the taxpayers a buck 20 for the truck to idle that hour. MUCH cheaper than
turbo bearings, less fuel than it'd take a cold engine to struggle with load,
etc.
Hope this helps,
David
This archive was generated by hypermail 2b29 : Tue May 01 2001 - 07:42:41 PDT