Tom Quackenbush wrote:
Christopher Tidy wrote:


Tom Quackenbush wrote:


snip

In my experience diesel engines start much more easily in cold weather
(and after long idle periods) than traditional petrol engines which
employ a carburettor. Two days ago I started up a bakhoe loader which
hasn't run for 4 1/2 years. Needed a new battery but then it fired up
straight away. I didn't even have to drain the fuel tank. You'd be lucky
to do that with a simple petrol engine.


What was the temperature when you started it?

This time it was probably 18 C, so okay, not cold. But I've started the
same machine after long idle periods when it's below 0 C with no
problems at all. It has a "cold start" button which causes the pump to
inject more diesel, raising the compression ratio and sealing up any
leaks around the pistons. Works great! I've also had big problems
starting petrol engines in warm weather. Just my experience...


Okay. Just wanted to distinguish between fuel stability and cold
weather starting. I'd expect diesel to remain viable longer than
gasoline (petrol), but it would be harder to start in cold weather.

OP only mentioned sub-freezing temperatures, so that's not too harsh
a test for either fuel. I'm not sure how well diesel would fare in
sub-zero (Fahrenheit) temps, though, esp. if it was a warm weather mix
and had no added engine heating (e.g., electric block heater).

I have my own, loosely related, anecdote. I left my Unimog sitting
in a field for almost 2 years (long story). It sat through two Vermont
winters without the batteries being charged. The batteries were a pair
of Wal-Mart's cheapest. I thought that it was a foregone conclusion
that the batteries would be completely ruined; that is, completely
self-discharged and subsequently frozen in the sub-zero (F) temps.
When it became a priority that I start the 'Mog this Spring, I went
down to the field equipped with 2 new, charged batteries, ether, and
fresh gas. After adding the fresh gas (petrol), but before changing
out the batteries, I decided to try the ignition button. It turned
over! It kept turning over for 20-30 seconds until the fuel line was
primed and then the engine started and ran fine. This does not fit
with anything I thought I knew about lead-acid batteries.

Yes, I sometimes find that I encounter these situations where rules of
thumb are broken completely. Fortunately in your case it was a nice
surprise, although I guess you still ended up with two extra new batteries.

I believe that there are several different kinds of lead-acid batteries.
The most traditional has electrodes made from a lead-antimony alloy, and
is quite resistant to deep cycling but needs to be topped up with water
fairly often. "Maintenance free" batteries use a lead-calcium alloy for
the electrodes and rarely need to be topped up with water, but are
rapidly damaged by deep cycling. I believe lead-calcium batteries also
need to be charged to a slightly higher voltage. There are a few other
more complicated kinds of lead-acid battery too.

Best wishes,

Chris