I was under the impression that cranking for a good 30 seconds is fine....is that too long?

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Yes, 30 seconds max is ok but the cool down time after that seems like an eternity. Generally it's between three and five minutes depending on the starter manufacturer and ambient temperature.

Over the years I've come to the conclusion that more starter damage seems to happen (in general) from cranking with a low battery than most would expect. The starter gets hotter and the operator tends to try harder / more often since the car often seems "so close" to firing up. I've disciplined myself to walk away and allow whatever time is needed to bring a battery back to substantial charge when I get to that point. No matter what I was trying to do, the car often fires up on the first shot once battery charge is restored.

Good chance to let the battery charger or jump car charge the battery in your diesel for a bit.

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When life gives you lemmings... make lemmingade.

In twenty years of working on these cars, I've never found any value at all in cracking lines and seals. When I need to prime the system, I fill the secondary with fuel and install as normal. The car starts as soon as you crank, and will stall after a few seconds. This is enough to work the fuel most of the way from the tank. A few extended cranks usually gets it all the way there, in the worst case a second fill of the filter may be needed. There is absolutely no need to "bleed air".

What I have found is that crud accumulation can prevent fuel from freely flowing into the reserve bowl (which is inside the tank). When the tank is more than 1/4 full, fuel will flow over the top and fill the bowl no matter what. But when fuel is low, all it takes is a little dirt to clog the baffle system. This can prevent the pump from priming. The solution for that is to take the tank out and wash it out thoroughly, or always drive with a quarter tank or more.

When I tried to restart after sucking dry.... and refueling, I found about 5 good long cranking sessions of about 30-40 sec each, with only a couple minutes between.... hoping to get re-primed.. was enough to melt connections of three of the brushes from their braided wires inside the starter.

Flatbed home.

"New" starter installed... then all the line cracking and bleeding air, etc. etc.. and much more cautious use of starter. Only two long crank sessions back to back allowed per 2 hours... trickle charing battery in between. Eventually fired up after a couple days.

Amazing thing is this was done on a 10 year old (maybe older?) Mercedes branded battery... that's STILL in the car today doing my daily starts. Amazing battery.

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Cheers!
Scott McPhee

1987 300D

this may be true on a perfect fuel system or a very low mileage vehicle...
however, if you run out of fuel, and your fuel lines are not new, or any leaks are present, or the IP is weak, or the lift pump is needing a new pressure spring, or (insert old vehicle excuse here) you WILL need to open the injector line nuts at the injectors to get the air out.
ESPECIALLY if before you refilled the filter, or the tank, you tried to crank the car and got a lot of air in the IP...

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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!