I know the 240D will continue to run without the alternator working (although if the belt snaps then its gonna overheat anyhow..)
but, is it possible (or advisable) to start the car without an alternator at all hooked up?
I ask because I had to pull an alternator from one 240 to put in the other, but now the one without an alternator needs to be moved..only about 50 yards, but it still needs to be moved (180 turn, across a busy street and up a driveway, so not really pushable)
Can I still start the car without an alternator hooked up? Will I mess something up?

I really don't like the idea of removing the alternator again, installing to move the car 50 yards, taking it back out and then re-installing again in the other one..!

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1981 240D ... 265k
1977 240D ... 265k
1977 240D ... 250k

if the battery has enough juice to crank it then it has enough to run for 50 yards.

Once the car is running, there's really not much load on the electrical system unless you turn on the headlights. You'll be fine.

I wouldn't drive hard, and I'd recommend shutting the motor off as soon as possible to prevent getting hotspots, but, yes, the car will do it fine. Tie a string around the water pump pulley and the crank, and there will be no issues all day. Unless you run the AC

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

ok, cool. thanks for the tips. It will literally take less than 1 minute to get the car where it needs to go, so I'm not too worried about overheating. and the a/c isn't attached anyhow, so good there too!
I just wanted to make sure I wouldn't screw up the electrical system any without the alternator in the circuit.
its hot here in Los Angeles, so it prob won't even need the glow plugs to get started, it starts like a champ... now if only the transmission would shift i'd be in business with this car (that's why I'm not rushing out to get another alternator for this car)

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1981 240D ... 265k
1977 240D ... 265k
1977 240D ... 250k

The battery + connects to the alternator (via the starter), so at least tape/cover the cables that connect to the alternator so they don't touch anything and short.

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'82 300TD
'77 6.9
'75 280S
'74 280
'87 Porsche 944 turbo

Running the vehicle with a battery and no alternator is ok.
Subject to the caveats above - water pump needs to run and protect the alternator cables from shorting.
I have heard of many good emergency belts - rope, shoe string, even women's pantyhose.
Disconnecting the battery while the alternator is producing electricity is bad.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

Having run various engines in all sorts of partial assembly, what you want to do is a non issue. Loads are low and run time short. It is good to ask when going beyond normal operation.

First, a diesel runs lots of air through the cylinders, this provides cooling. ( and is why idling a diesel for long periods is a bad thing as it causes incomplete combustion / wet stacking.) Some gasoline cars deactivate fuel to cylinders allowing air to pump through when coolant is lost.

Second, A full cooling system when cold is a huge heat sink all on it's own even if coolant isn't moving.

Third, At some point a thremo siphon effect will occur circulating coolant. ( However some systems might not thermo siphon due to rad hose / thermostat configuration. )

Fourth, think about what happens when a belt is thrown with a hot motor when driving down the road. The fan will windmill for a while but will slow as road speed falls off. There will be much more at "temp" engine operation than a cold start across the yard.

I've run engines with zero coolant farther than the distance you are wanting to. When running sans coolant I pull the belt to prevent overheating the water pump seal.

Just insulate the alt wires ( a rag is fine )

Great, thanks everyone! Not only am I happy I can do this, but I've learned more yet about the workings of my cars!

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1981 240D ... 265k
1977 240D ... 265k
1977 240D ... 250k