Why do 617's require less glow time then 603's?? - PeachParts Mercedes-Benz Forum

Hatterasguy · #1 01-23-2006, 12:27 PM

Ok I have noticed this and have been wondering why for awhile? The 603's need to go through the complete glow cycle regardless of temp of they will skip and complian after you start them. While the 617 on the other hand doesn't seem to mind this, if the engine has some heat in it you can almost skip the glow cycle?

What did MB change? The glow systems are similer, I know the 603 has a different head design maybe that is the cause? I think the glow plugs are even that same?

Any ideas?

DieselAddict · #2 01-23-2006, 01:21 PM

Any chance that your 617 has the newer relay with afterglow?

Pete Burton · #3 01-23-2006, 01:28 PM

because the 617 is better

speedy300Dturbo · #4 01-23-2006, 01:29 PM

Because there is one less glowplug that needs to be heated up?

Brian Carlton · #5 01-23-2006, 01:40 PM

Yep, I see the same thing.

The 603 is a cold beast. If you don't wait at least 15 seconds, it's going to let you know it. Also, it needs the glow when it's warm as well. If you simply crank the key without a glow, it takes a few seconds to start.

The 617 starts and runs almost like a gasser. Just unbelievable with the new valves and new prechambers. No smoke.......no roughness.........just a bit of a low idle.......that's it.

Can't make a guess as to why..........but the two of them are vastly different.

Rick Miley · #6 01-23-2006, 01:45 PM

I think that's a function of the aluminum head on the 603. Aluminum, being such a great conductor of heat, will suck all the heat out of the prechamber.

Hit Man X · #7 01-23-2006, 03:26 PM

It's about a wash for my vehicles as the SD's starter is a bit weak. Once warmed up, then stopped for let us say for 15min... the 603 needs to have a full glow cycle again versus a partial on the 617.

andmoon · #8 01-23-2006, 03:32 PM

My 603 doesn't need the full cycle unless it's a fully cold start.
My departed 617 needed more gp than my 603.

dieseldiehard · #9 01-23-2006, 03:41 PM

I've often thought about the differences too. My 603 (recently rebuilt) still takes more cranking to light er off, especialy cold!
My 617 turbo goes off with such a twitch of the key its unbelieveable to me at times I can count one thousand one, one thousand two and the engine is running already and time to get off the starter motor before I got to the second one in one thousand one! The engine has new pistons and was bored and hones 1st oversize so compression is super that helps I am sure. OTOH my '83 300D with almost 250K on it and the original head still on the engine needs a few more cranks, maybe three seconds when cold. I believe that compression has all to do with this. When I get my latest '87 300D turbo running after re-ringing it, I'll be able to comment on how a 603 is "supposed to start" but I still figure its going to be way different than a 617. The 603's always seem to rattle when cold too, it has to be air in the lines but there are no leaks around my fuel delivery nozzles or injectors so where would any air come from? I generally try to do the two-step glow plug warming procedure too, it makes a small difference in the crank time it takes to get the engine running but seems to me that makes no difference in the rattling noises when the engine is cold and starts running. And I don't mean really COLD, even an ambient of 45 degrees (F) is enough to make more rattling than say a relativel warm 60 degree day. Something is really sensitive in the 603 engine!

pawoSD · #10 01-23-2006, 05:14 PM

Quote:

Originally Posted by Pete Burton

because the 617 is better

I agree.

I never do a full glow cycle, unless its REAL (negative F) cold out.....normally I just wait 5-10 secs tops, even when its in the teens, it was only 14 out this morning when I went to leave, I glowed right around 10 secs, cranked, and 2-3 cranks later it was runnin'.

Heck, when its cold like that, even when its not cold, our gasser van takes 6-7 cranks to start, always does.....its thirst for oil that has developed probably doesn't help anything either.

80k on it and 1qt every 1k, disgusting.

#11 01-23-2006, 06:11 PM

Quote:

Originally Posted by Rick Miley

I think that's a function of the aluminum head on the 603. Aluminum, being such a great conductor of heat, will suck all the heat out of the prechamber.

I suspect you're correct. The Al head will disperse heat more quickly, while the Iron has more thermal inertia and lower conductivity.

rhodes2010 · #12 01-23-2006, 07:36 PM

I remember recently reading an answer in a tech
column for gasser v8's where the writer asked why aluminum heads
allowed higher compression, and the answer was that aluminum heads
demanded greater compression to compensate for the different heat pattern
(heat loss faster than a cast iron head).

I only have a 617 engine, and it certainly starts easy. Feel guilty not
waiting for the glow plug light to go out.

Hit Man X · #13 01-23-2006, 07:42 PM

That theory was disproved regarding aluminum allowing higher comp versus iron. CarCraft dyno'd a SBC with Dart heads, check it out. Interesting stuff.

Total timing advance curves, comp ratios, etc.

Steve Gold · #14 01-23-2006, 08:44 PM

Seven seconds is the time it took a new plug to get up to nearly white hot when tested on the battery,So this is what i give it (see sig) The heater part of the plug is not in contact with the head or chamber and is there to light up the diesel spray upon injection.

All this talk of cranking makes me wonder if something else is not right, every deisel I have ever had fired right up with the first piston to go over the compression stroke.

Steve

kmaysob · #15 01-23-2006, 08:48 PM

Quote:

Originally Posted by Pete Burton

because the 617 is better

i second that