I let the 300SD sit for two weeks (high diesel prices).
Went to start it and it would not.
I have been driving this car 3,000 miles a month for 5 years.
It is used Tuesday through Friday every week.
Always change the oil every 3,000 to 3,500.
Fuel filters are not too old.

My first check was to remove all glow plugs and test each for glow
and removed valve cover and adjust valves. (I have to admit I failed the
every 15,000 valve adjust, been about 40,000).
Glow plugs glow strong connected to battery charger.

I checked the voltage at glow plugs and it seems okay.

The last thing is the battery, wore it down, pretty quickly, trying to fire up.
It sort of started only once, then died.

It will not crank fast enough using jumper cables.
Then I looked at the battery and realized it is 10 years old (from 2001).
So off to purchase a battery.
Although I really should just pull the new battery out of the 300D and
use that as a test.

I checked the glow plug relay to glow plug connector for good contact.
Cleaned it, crimped the connectors for tighter contact.

I also keep a glow plug bypass kit handy to send 12 volts straight to the
glow plugs in an emergency. This did not help or matter so I switched back to relay.

Anyone want to chime in some ideas ?

I probably should have checked compression while I was in there.
But was afraid it would be bad news.

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80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
02 Z71 Suburban 117,000
15 Toyota Prius 2600 miles
00 Harley Sportster 24k
09 Yamaha R6
03 Ninja 250