B Marques

I am new to Mercedes diesels and have a question. I know vw you are supposed to leave the key on the on position for a few seconds to warm up the glow plug before starting, but how do you do that on a Gl350 with the push button start? Is it okay to just start it dead nj winter?

N_Jay

When you hit the button the Glow Plugs will come on and then the starter starts turning a faction (or longer) of a second later.
The colder the engine the longer the wait.
(Up to about 1 1/2 or 2 seconds, but that was at -12 after a -20 night)
Of course at that temp the fuel was almost gelled so I ended up with a check engine and bunch of error codes. (I had filled up on a trip in a warmer area. Local fuel probably would have been fine.)


P.S. Elizabeth NJ is NOT cold.

Fourdiesel

The start sequence on the Mercedes diesels is automatically programmed. You cannot alter it. The engine management system 'knows' all the important parameters, turns on the glo plugs for the required length of time [if necessary at all] and THEN closes the start relay. When the engine starts to crank the first injector pulse is very short to easily start the burn and heat the gasses for later injection pulses on the same ignition event. It is possible for each pizeoelectric injector to put up to 5 separate pulses into the cylinder at each ignition event in each cylinder. The above is true for a key or a start button.

drgeeforce

The glow plug is similar to an incandescent lightbulb it is on instantly. 1 sec is all it needs.

N_Jay

You should do some reading on the current glow plug systems.

drgeeforce

Bosch has a nice glow plug that gets hot fast, How do I know? I replaced a set already. Bosch plugs reach 1300C within 1-2 sec.

http://aa-boschap-fr.resource.bosch....rzenfolder.pdf

You must be thinking of Volkswagen's slow-glow and quick-glow systems.

http://www.4crawler.com/Diesel/GlowPlug.shtml

N_Jay

Funny, your link says 2 to 4 seconds depending on the version.


My point is it is;
1) It is not " . . . instantly. 1 sec is all it needs."
2) Start time is dependent on environmental temperature.

drgeeforce

You didn't read enough I have the Duraspeed which reaches 1300C in less than two seconds. 850C is the minimum temp where air is superheated by a 25:1 compression ratio and the addition of diesel fuel starts the combustion process. Very selective reading N_Jay... are you a lawyer?

N_Jay

I read just fine:

Does he have what you have?

Are the MB OEM glow-plugs Duraspeed?


Not a Lawyer, just an engineer!

drgeeforce

OEM plugs for the KeylessGO are supplied by Beru. Beru plugs will have a 1-2 sec delay after pushng the KeylessGO start button down to -25C. MB has implemented the BORG/Warner ISS (instant start system) to reduce the starting time similar to gasoline engine starts.
http://www.beru.com/bw/taxonomy/term/35/all

Since B Marques drives a 2010 GL350 similar to mine with the KeylessGO, he doesn't have to worry about glow plug warm-up time. Although I didn't replace with OEM Beru, IMHO find Bosch Duraspeed plugs equal or superior to Beru. The reason why I went with Bosch is because we go skiing and having the quick starting hot plugs, plus a bottle of PowerService Diesel 911 in the tank, puts my mind at ease. In CA, most diesel is B5 and Propel Fuels dispenses B20, I am very familiar with cold starts. REST is a godsend.

drgeeforce

You might want to consider PowerService DIESEL FUEL SUPPLEMENT® Arctic Formula if you are having cold start issues.
http://www.powerservice.com/dfs/

N_Jay

It would be interesting to know if the GP difference really makes a difference.
Seems the controller turns them on and sets the delay based on the intended not installed GPs.


Either way, on a modern MB (Keyless-Go or not) there is nothing you can do. The start cycle is controlled by the car. There is a short delay when you go to start. The delay is a bit longer in cold weather.


(And modern GPs heat up "very quickly" but not "Instantly"!)

drgeeforce

The ISS is MOSFET feedback controlled and operates on Pulse Width Modulation. It is not a programmed time interval, but voltage and temperature-time dependent, therefore a faster heating plug will offer quicker start times, and reduced voltage demand/drop during startup. PWM utilizes the more efficient voltage distribution to each individual GP separately, not across the board.
http://www.beru.com/download/produkt...atz_iss_en.pdf

The next gen GP utilizes a pressure sensitive GP that senses the opening of the exhaust valve, shutting off the voltage, and turning on when pressure rises, providing a more efficient combustion, therefore reducing NOx gases.

The difference between an instant(1 second) and sub-2 seconds may be astronomic to an engineer and the space program, but for a diesel engine, it is but a blink of an eye, or about 0.4 seconds.

N_Jay

If the feedback is provided by the Resistance/Temperature curve of the plug, is there a change that a non OEM plug will actually be performing out of spec?


If it is slightly overheating the consumer would probably never notice the extra current used and slightly shortened GP lifespan.


If it is slightly under heating, unless they are very conscious they may also never notice the difference in crank time, but might be subjecting the DPF to higher soot loads during start up.


As for the difference, during a particularly cold day my wife reported that something was wrong with the GL because she had to push the start button several times to get it to crank. (Obviously it was waiting to heat when she hit the button a second time shutting it off)
I explaining that cranking would start a second later in cold weather, and she should just wait.

drgeeforce

Bosch Duraspeed GPs like most ceramics have a steeper resistance curve, allowing for faster temperature rise at constant voltage range of 4.4-5V. If MBUSA collaborated with Borg/Warner to set off a CEL/DTC if the resistance was too low, maybe that would set off a service code, but I have not encountered a low value setting.

AFAIK the goal of the ISS is to combine maximum current flow while the PWM minimizes voltage drop across the charging. The resistance rise during warmup secondary to increasing temperature signals to the controller unit located on the engine block to actually decrease current and voltage. The only signal to the controller unit indicating a faulty GP is a infinite high resistance signal causing the controller to either not start or cut off voltage to the GP. DTC would indicate which cylinder had no voltage, indicating a bad GP. On the Sprinter, the DTC is usually both a P0380 general glow circuit fault and a P067x individual-cylinder fault where x = 1 through 5, identifying the number of the cylinder with the failed plug.

N_Jay

Well, the only error I have received was a failed GP controller.
I think I bought it that way, but being a TX car and it showed the error on the first restart in sub freezing temps (on the drive home).


Guessing the current curve is a bit differed between ambient temps above and below freezing, and the higher current showed a latent failure (Either that of my 'normal' luck kicked in?)

drgeeforce

The current curve looks more like a downward staircase. As the engine temp rises the current drops in a stepwise fashion as temp/resistance increases. If your GP controller had no voltage, it would explain a no start. Low Voltage would give an error code. Current is a function of wires and battery. I would check the wires from battery to GP if there was a long delay. A high current reading initially is normal but a sustained high current may indicate a relay solenoid frozen in the on position causing an early demise for your plugs. Cold weather starts are usually battery dependent, taking it to a shop and testing the CCA is probably in order. Finding a shop with a Spectro is rare but a carbon pile or DC load will infer a good battery from a sulphated one.

N_Jay

It started fine, other than a longer than normal wait and slightly longer than normal crank, and a tripped MIL with the code for a failed GP controller.

I am guessing the controller (or the ECU) has a "failsafe" or fallback mode when it finds and internal fault so the GPs get a fixed light time and voltage.

Replaced the controller with the updated part and all is well.

chsu74

People usually magazine race on car forums with 0-60 numbers. This is the first I have seen with glow plugs...

Fourdiesel

It's a diesel thing! lol

N_Jay

We "Oil Burners" are special!

drgeeforce

Magazine racing? Diesels are not racers, although we have upgrade kits to improve performance, just like the gassers.

Kleeman's KD box can upgrade the HP: http://www.kleemann.dk/Performance/tuning/Kd-box

JEGS has the PowerPuck: http://www.jegs.com/i/DiabloSport/31...FQWTfgodhJQANw

RENNTech has ECU kits: http://www.renntechmercedes.com/www/catalog/360

BRABUS has a 0-60 in 7.1 sec kit: http://www.brabus.com/en/raster.php?...94&kategorie=9

chsu74

^ my GL is the safe family vehicle. For speed, my BMW 550 and Porsche turbo scratches that itch.

N_Jay

That what you say.


I'll take my Diesel, over an gasser with the same HP when pulling a 3500 LB trailer!

drgeeforce

LOL. I'll bet you love watching Draught Horse racing and Tractor Pulling too!