"Engine starts immediately" Is this a good thing? - PeachParts Mercedes-Benz Forum

Mister Byrnzoil · #1 03-09-2008, 10:34 AM

For the first time ever on any of my vehicles, the glowplug light failed to light on my coupe the other day, the thermometer said 35 F, car had not been started in a week. I turn the key off and try it again, still no light, I turn the key off again and turn on the dome light, cycle the key on again and nothing, no dimming.

Well this engine runs great.. lets see what happens... I had to crank it for maybe 15 seconds till it coughed once then died, then cranked another 10 seconds till it fired up and idled. While I was cranking the oil pressure came up after about 5 seconds to almost 2 bar.

I like the fact that I had oil pressure before it fired, and I wouldn't have a problem if I had to crank the car for 3 to 5 seconds until it fired, I don't know if it would cause undo wear on the starter or gears, or too much unburned fuel in the cylinder?

I'm not necessarily advocating this... just want to discuss the pros and cons of a longer crank time.

FYI-This thread is not about fixing my glowplugs.

nhdoc · #2 03-09-2008, 10:37 AM

It's unclear what you are asking exactly but yeah, it puts unecessary extra wear and tear on your starter and battery to crank heat into the engine rather than have working GPs so generally the recommendation would be to fix the GPs and save the starter and battery.

Lexxani · #3 03-09-2008, 10:49 AM

cold cranking a diesel w/o growplugs opporational. . lemme tellya bout fun, but getting it started. .good work. Ive never had to fire my 6.2 detroit up in that weather, but after 3 cycles in the low 50s (ambient temp) I could always get mine going w/o glowplugs, however I think after some time it took a toll on my starter (possibly due to age or country of origin-america). . .

pimpernell · #4 03-09-2008, 10:53 AM

Quote:

Originally Posted by Mister Byrnzoil

For the first time ever on any of my vehicles, the glowplug light failed to light on my coupe the other day, the thermometer said 35 F, car had not been started in a week. I turn the key off and try it again, still no light, I turn the key off again and turn on the dome light, cycle the key on again and nothing, no dimming.

Well this engine runs great.. lets see what happens... I had to crank it for maybe 15 seconds till it coughed once then died, then cranked another 10 seconds till it fired up and idled. While I was cranking the oil pressure came up after about 5 seconds to almost 2 bar.

I like the fact that I had oil pressure before it fired, and I wouldn't have a problem if I had to crank the car for 3 to 5 seconds until it fired, I don't know if it would cause undo wear on the starter or gears, or too much unburned fuel in the cylinder?

I'm not necessarily advocating this... just want to discuss the pros and cons of a longer crank time.

FYI-This thread is not about fixing my glowplugs.

What would be the benefit of having to depend on a car that can start at 35 degrees without glowplugs, but cannot start at 20 degrees without glowplugs?? The other issue is the extra stress placed on the starter and battery. If this is just an extra car that you do not depend on, I guess you can see how low the temperature can go before it won't start, but if is your daily driver, I would bite the bullet and fix the glowplugs.

Stevo · #5 03-09-2008, 10:54 AM

One of the advantages of synthetic oil is that it stays up in the engine longer keeping parts protected and making starting in colder weather easer.

Mister Byrnzoil · #6 03-09-2008, 11:10 AM

I have already fixed the glowplugs.

Let me try to clarify my question...

Lets say your car would start reliably in the summer w/ 3 seconds of cranking and in the winter w/ 5 seconds of cranking... would this be an acceptable trade off to have some oil pressure before the engine starts.... Oil company advertising has impressed upon me that most wear on an engine occurs during startup... don't know if its true or not.

Yes Stevo, you are right, I forgot to mention 5w-40 rotella semi-synth. The right oil does make a difference in cold spinning the engine.

nhdoc · #7 03-09-2008, 12:05 PM

Oh, so your question is about building oil pressure by cranking rather than starting immediately...now I see.

No, I don't think there is a big advantage doing that. In fact, if you have even a synthetic mix in there you are getting good coating on the parts before it starts.

Think about all of these old diesels with 2,3 and even 400K miles on them that didn't "pre-oil" before starting...the engines will do just fine starting right up after glowing and you don't have to crank them to build oil pressure.

Jeremy5848 · #8 03-09-2008, 01:28 PM

My mechanic commented to me once that it was important to NOT start Mercedes diesels any more often than necessary. He advocated locking the car with a spare key and letting the engine idle while you [for example] run into school to pick up your kid. His reason for doing this was that the overhead camshaft will "drip dry" in its exposed position on top of the engine and so will have little oil for the first couple of seconds after starting.

Whether it's worth cranking the engine (with the fuel shut off) until the oil pressure comes up is another matter. Yes, it might help the engine but the wear and tear on the starting system (battery included) probably would negate any benefits. And the fact that so many of us have 200000+ miles on engines shows that it isn't a serious problem.

But it's an interesting thing to think about. Thanks for bringing up this subject.

Jeremy

nhdoc · #9 03-09-2008, 01:51 PM

Quote:

Originally Posted by Jeremy5848

My mechanic commented to me once that it was important to NOT start Mercedes diesels any more often than necessary. He advocated locking the car with a spare key and letting the engine idle while you [for example] run into school to pick up your kid. His reason for doing this was that the overhead camshaft will "drip dry" in its exposed position on top of the engine and so will have little oil for the first couple of seconds after starting.

I guess everyone IS entitled to a crazy theory...that is the first time I have ever heard this one though.

#10 03-09-2008, 02:24 PM

If you are really concerned, install an electric pre-lube oil pump. I haven't seen one recently, but they used to be popular with hot rodders.