Cold Start Tips Needed! - Page 3 - PeachParts Mercedes-Benz Forum

whunter · #1 12-14-2010, 11:33 PM

Quote:

Originally Posted by warmblood58

Damn, car almost did not start this morning in Vail -temp was 9 degrees. Glow system is perfect, battery was strong (this car always starts) and I had winter diesel fuel in tank. What I did not do was plug the block heater in the night before -no outlet available! So engine was cranked about ten -twelve times with no fire! Fortunately, a guy next to me allowed me to jump off his truck which helped but for a while, I was beginning to think that my always highly reliable OM617 was not going to start ('82 300SD)

So hey cold weather brothers, what are your cold start tricks when in dire straits?

Winter Cold starting issues are 98%:

#1. Bad glow plugs
#2. Valves not adjusted
#3. Weak battery and/or starter
#4. Bad/Poor ground from body to engine
#5. Engine oil to thick for the ambient temperature/climate.

Winter Cold starting issues that are 2%:

* Plugged filters
* Diesel jelled = summer fuel, contaminated fuel and/or extreme cold ambient temperature.
* Bad o-rings and/or hoses leaking air in the fuel system when cold.

Glow plugs link thread All diesel models
http://www.peachparts.com/shopforum/diesel-discussion/137732-glow-plugs-link-thread-post1019018.html

Starter health is important to your diesel!!!
http://www.peachparts.com/shopforum/diesel-discussion/107318-starter-health-important-your-diesel-post739798.html

Cold weather starting links
http://www.peachparts.com/shopforum/diesel-discussion/137674-cold-weather-starting-links-post1018529.html

.

Beagle · #2 12-15-2010, 04:35 AM

Quote:

Originally Posted by whunter

Winter Cold starting issues are 98%:

#1. Bad glow plugs
#2. Valves not adjusted
#3. Weak battery and/or starter
#4. Bad/Poor ground from body to engine
#5. Engine oil to thick for the ambient temperature/climate.

Winter Cold starting issues that are 2%:

* Plugged filters
* Diesel jelled = summer fuel, contaminated fuel and/or extreme cold ambient temperature.
* Bad o-rings and/or hoses leaking air in the fuel system when cold.
.

Really, the above are not so much “Cold Starting Issues” as routine maintenance issues. It is rather futile and pointless to discuss specific cold starting problems before it can be assumed all of the above have been addressed and eliminated.

Conditions for start are at their peak at the first cycle of injection and it is essential that fuel be injected at this time as they deteriorate very rapidly thereafter. If well-atomized fuel is injected into a combustion chamber on the 1st cycle with a white-hot glow plug and hot air it WILL vaporize and ignite - no ifs, buts or maybes. It’s not a compression issue. Churning over the engine serves only to bleed the fuel system and flatten your battery – the golden opportunity has been missed!

Over 90% of genuine cold start issues are injection or start technique related – i.e. Fuel has not been injected from the critical first cycle and this can usually be easily fixed (leaking D-Valves ~ injector pintels ~ fuel lift pump). If your car does not fire on the first pot in summer every time you have a delivery problem that will haunt you in winter.

After browsing through a few of the above linked threads I was unable to find one post that described the correct cold start procedure.

whunter · #3 12-15-2010, 10:52 AM

Quote:

Originally Posted by Beagle

Really, the above are not so much “Cold Starting Issues” as routine maintenance issues. It is rather futile and pointless to discuss specific cold starting problems before it can be assumed all of the above have been addressed and eliminated.

Conditions for start are at their peak at the first cycle of injection and it is essential that fuel be injected at this time as they deteriorate very rapidly thereafter. If well-atomized fuel is injected into a combustion chamber on the 1st cycle with a white-hot glow plug and hot air it WILL vaporize and ignite - no ifs, buts or maybes. It’s not a compression issue. Churning over the engine serves only to bleed the fuel system and flatten your battery – the golden opportunity has been missed!

Over 90% of genuine cold start issues are injection or start technique related – i.e. Fuel has not been injected from the critical first cycle and this can usually be easily fixed (leaking D-Valves ~ injector pintels ~ fuel lift pump). If your car does not fire on the first pot in summer every time you have a delivery problem that will haunt you in winter.

After browsing through a few of the above linked threads I was unable to find one post that described the correct cold start procedure.

If everything is perfect:

* Turn key on to the glow position.
* Ignore the light.
* LISTEN for the clunk of the glow plug relay disengaging/turning off, (extreme cold -20° F or lower, you may need to glow twice before cranking in).
* Apply 1/10 - 1/8 throttle = just enough to assure the engine speed will be above 1000 RPM.
* Crank the engine up to 30 seconds .

#4 12-15-2010, 11:07 AM

Quote:

Originally Posted by whunter

If everything is perfect:

* Turn key on to the glow position.
* Ignore the light.
* LISTEN for the clunk of the glow plug relay disengaging/turning off, (extreme cold -20° F or lower, you may need to glow twice before cranking in).
* Apply 1/10 - 1/8 throttle = just enough to assure the engine speed will be above 1000 RPM.
* Crank the engine up to 30 seconds .

Under those conditions, I don't apply any throttle until the engine is actually starting to catch.

whunter · #5 12-15-2010, 12:02 PM

Quote:

Originally Posted by Craig

Under those conditions, I don't apply any throttle until the engine is actually starting to catch.

It varies depending upon linkage/idle adjustment.
On the 190d I give it 1/4 inch = just a light touch.
On my 300SD everything is perfect, no throttle needed.
Wifes car needs 1/4 throttle or it won't start below 20° F, tweaking/repairing ASAP.

layback40 · #6 12-15-2010, 05:16 PM

Quote:

Originally Posted by Craig

Under those conditions, I don't apply any throttle until the engine is actually starting to catch.

This is interesting Craig.
There is a good explanation for your experience.
On some old diesels You have to get them spinning before you fuel them or they wont get sufficient cranking speed & compression to start. It sounds like the same principle is working for you.
At some stage in the start cycle extra fuel is needed as the idle volume may not provide enough to maintain the running of the motor at the start. This fits well with your use of the throttle once it starts to kick.
Given the number of variables in play its not surprising that there are nearly as many starting techniques as there are cars!!

Adam,
Your observation of "hunting" is not that uncommon.
What may be happening is that the idle speed is dropping low enough for some sort of anti stall fueling to be triggered in the IP. That could be set at too higher speed or your idle could be too low. It happens some times on tractors with a similar types of IP. A good IP technician could adjust it. I think its an adjustment inside the back of the IP. There are way too many springs & leavers in there to DIY !!

vstech · #7 12-15-2010, 11:57 AM

Quote:

Originally Posted by whunter

If everything is perfect:

* Turn key on to the glow position.
* Ignore the light.
* LISTEN for the clunk of the glow plug relay disengaging/turning off, (extreme cold -20° F or lower, you may need to glow twice before cranking in).
* Apply 1/10 - 1/8 throttle = just enough to assure the engine speed will be above 1000 RPM.
* Crank the engine up to 30 seconds .

I would change one thing.
crank the engine up to 2 minutes... NO MORE!!! 30 seconds is not enough with a motor suffering from many starting issues, and letting off in short time will seriously prevent the motor from starting.
I agree, no throttle until the motor begins to catch.

whunter · #8 12-15-2010, 12:10 PM

Quote:

Originally Posted by vstech

I would change one thing.
crank the engine up to 2 minutes... NO MORE!!! 30 seconds is not enough with a motor suffering from many starting issues, and letting off in short time will seriously prevent the motor from starting.
I agree, no throttle until the motor begins to catch.

I did state If everything is perfect:

Durability testing proves that excess thermal loading begins/happens after 60 seconds of full load cranking on a perfect NEW starter.

If it does not start by then = there are issues that need to be fixed..

Beagle · #9 12-15-2010, 02:18 PM

Quote:

Originally Posted by whunter

If everything is perfect:

* Turn key on to the glow position.
* Ignore the light.
* LISTEN for the clunk of the glow plug relay disengaging/turning off, (extreme cold -20° F or lower, you may need to glow twice before cranking in).
* Apply 1/10 - 1/8 throttle = just enough to assure the engine speed will be above 1000 RPM.
* Crank the engine up to 30 seconds .

Copied verbatim from original MB “Owners Manual” for 240D/300D

"At temperatures below 0°C and with the engine cold, completely depress accelerator and clutch pedal while starting. Actuate starter until the engine fires regularly and engine speed rises. Then ease off the accelerator slowly."

This is a standard V cold start practice (< -10°C) and applies equally to all old indirect injection Diesel engines equipped with glow plugs and inline fuel pumps.

There is a very good reason for this – It ensures that you are getting sufficient fuel injected on all 5 cyl’s on that critical first cycle. Fuel volume @ full boost full throttle is 44mm³ / cyl on the 617 engine (about the size of a 4mmØ ball) and at idle just a very small fraction of that!

Regarding The Pre-glow:

Quote FSM - “After a glow period of 9secs a temp. of 900°C is attained and after 30secs the max. temp of 1180°C is reached. Cut-out between 30 sec and 1 min depending on ambient temp.”

There is little point in glowing for more than 15 sec and in any case it should be less than half the glow cycle time to allow start before cut out. The glow plug is the primary source of ignition for a very cold start and after cut out you will be relying solely on auto-ignition.

Just BTW: The auto-ignition temp of #1 Diesel is 210°C, almost 40°C lower than #2 Diesel.

whunter · #10 12-15-2010, 02:51 PM

Quote:

Originally Posted by Beagle

Copied verbatim from original MB “Owners Manual” for 240D/300D

"At temperatures below 0°C and with the engine cold, completely depress accelerator and clutch pedal while starting. Actuate starter until the engine fires regularly and engine speed rises. Then ease off the accelerator slowly."

This is a standard V cold start practice (< -10°C) and applies equally to all old indirect injection Diesel engines equipped with glow plugs and in-line fuel pumps.

There is a very good reason for this – It ensures that you are getting sufficient fuel injected on all 5 cyl’s on that critical first cycle. Fuel volume @ full boost full throttle is 44mm³ / cyl on the 617 engine (about the size of a 4mmØ ball) and at idle just a very small fraction of that!

Regarding The Pre-glow:

Quote FSM - “After a glow period of 9secs a temp. of 900°C is attained and after 30secs the max. temp of 1180°C is reached. Cut-out between 30 sec and 1 min depending on ambient temp.”

There is little point in glowing for more than 15 sec and in any case it should be less than half the glow cycle time to allow start before cut out. The glow plug is the primary source of ignition for a very cold start and after cut out you will be relying solely on auto-ignition.

Just BTW: The auto-ignition temp of #1 Diesel is 210°C, almost 40°C lower than #2 Diesel.

That is on a NEW "PERFECT" engine.

The FSM also tells you to use gasoline for better cold starting, there is a TSB that superseded that, and now specifies kerosene.

As to the extended glow or double glow, my data is correct.
Later models incorperated the after-glow function into the glow plug relay for easier starting and emissions.

The hotter the pre-chamber = easier start.

#11 12-15-2010, 04:09 PM

Quote:

Originally Posted by Beagle

Copied verbatim from original MB “Owners Manual” for 240D/300D

"At temperatures below 0°C and with the engine cold, completely depress accelerator and clutch pedal while starting. Actuate starter until the engine fires regularly and engine speed rises. Then ease off the accelerator slowly."

I don't see that method working with mine; any throttle at all makes it more difficult to fire initially. I have started mine at about -5F, but I had to pre-glow several times and crank for a while (with no throttle).

toddyvol · #12 12-15-2010, 04:24 PM

Last week It got down to 17 gegrees here. Car sat out all night and was not plugged in. My battery was very weak, thus no starting. New battery and car fired instantly after glowing two full cycles. I did squirt WD-40 in the air inlet just before cranking. I'm not sure if the WD-40 did any good.

okyoureabeast · #13 12-15-2010, 04:48 PM

My car stars fine, but if I leave the car in park or neutral the idlestarts lobbing ( goes down and up). I figure this is the lift pump. Any ideas?

Quirky Mercy · #14 12-15-2010, 10:37 PM

No problems this morning. one glow and it started like normal. I only plugged it in for 50 minutes. I will try it without the heater tomorrow. I think the Kero made a big diference. I am going to ohm the glow plugs when I can get it back in the barn. What reading is acceptable?

whunter · #15 12-16-2010, 12:45 AM

Quote:

Originally Posted by Quirky Mercy

No problems this morning. one glow and it started like normal. I only plugged it in for 50 minutes. I will try it without the heater tomorrow. I think the Kerosene made a big difference. I am going to ohm the glow plugs when I can get it back in the barn. What reading is acceptable?

The Ohm test is not reliable.

0.7 is what a NEW glow plug reads.
0.8 is IMO marginal.
Any other reading = replace them.

Reading material on the issue.

Trusting an OHM test is a common diagnostic error on glow plugs.
The glow plug is a HIGH temperature heating element = the element can (and does) frequently read OK on an OHM test but is bad/shorted.
The critical factor is electrode resistance at full operating temperature, testing at low ambient is not valid.

Heating to a minimum temperature of 850°C is critical for diesel engine start-up.
Glow plugs run 1000° - 1300°C = up to "2372° Fahrenheit" optimal temperature range.
This is why many members choose to remove the glow plugs, put them in a vice, and manual glow them (often finding bad units that OHM good).

The older Mercedes Benz diesels (pre CDI) have a Pre-combustion Chamber that houses the glow plugs.
Carbon build up on glow plug electrodes acts as an insulating blanket, reducing durability life and making the glow plugs ineffective.
Every time the glow plugs on engines equipped with a pre-combustion chamber are replaced, it should be reamed out to remove any carbon build up.

http://www.wellmanautomotive.com/glowplugs.php

http://www.ngkspark.com.au/glowplug_info.php#

http://www.ngk-dpower.com/en/technik/keramik-gluehkerzen/

Excellent study material.

Glow plugs link thread All diesel models
http://www.peachparts.com/shopforum/showthread.php?p=1019018

Starter health is important to your diesel!!!
http://www.peachparts.com/shopforum/showthread.php?p=739798

Cold weather starting links
http://www.peachparts.com/shopforum/showthread.php?p=1018529

Have a great day.