Mercedes Benz G 300 Problems
 

Hi I have a G300 Diesel 1999 and I rebuild the engine, I have good compressions but I have the problem that I feel it doesn`t have a good displacement and hills the car don`t respond the speed I reach is no more that 40 to 60 Km per hour, the engine sounds good but the speed is not what I spect, I don`t know if the problem is at the vacum circuit or if I need to cincronice the transmition computer with the engine computer.
Thanks you for the help and sorry for my poor english.
Have a good day.
Jose

José, where are you based? Can you read and write Spanish? If so, try the Spanish GWagen Club forum: http://www.clubmercedesg.es

In any event, I am a bit confused about your G. Is it the OM606-powered G300 Turbodiesel? I say this because I know of no G300 Diesel made as late as 1999. As far as I know, the G300 Diesel was discontinued in 1994. If this is the case, the Spanish forum is your best bet because as far as I know there are only 3 units of the G300 Turbodiesel in the USA....

Cheers

Assuming you have an OM606 engine, I can probably help you figure out what is wrong.

Have you verified the injection timing and all the mechanical settings? If these are all OK, then:

Most likely the EGR system is not working. There are several causes.

Does is there a strong vacuum available at the vacuum modulators for the EGR and the turbo? If not this needs to be fixed first.

After starting the engine, verify that vacuum gets all the way to the turbo vacuum solenoid. Drive around for more than 2 minutes. Check again. If the vacuum is gone now this means that the computer believes that the turbo *or* the EGR is defective. The fault could be in many places. Don't replace anything expensive yet!

Looks like problems with EGR, I have seen same problem just few days ago.

Diagnosis for "OM606 - No Power"
 

Here is how the system works:

On startup, the ECU operates the turbo normally (wastegate closed) and keeps the EGR closed too. Then after one minute it assumes that the EGR is a bit warmed up and tests it by opening and closing it a few times. It checks the movement of the EGR valve with a sensor on the back of the EGR. If the EGR is stuck, it turns off the turbo until the engine is restarted.

Things that can go wrong.
1) No vacuum in system (rare, but hoses do leak or get pulled out)
2) EGR vacuum modulator does not work or is slow (pretty common)
3) EGR sticks (very common)
4) TURBO vacuum modulator does not work or is slow (less common)

I have tried to fix a vacuum modulator. Not successful, even after several tries. Don't waste your time. Test with a known good one before buying.

The EGR can be loosened up with carburetor cleaner and manual cleaning. After you get it working you should think about putting a plug into the big exhaust line. Do not plug the EGR vacuum line. That is the same as causing #2 failure. The engine computer will spot the plug right away.

Note for the US readers: The plug in the exhaust line does not work for the 98 & 99 E300DT. The engine management software is different and this plug will be detected too.

Aren't diesel models sold in Canada? Perhaps not this model. The G Wagen seems like a natural choice for a diesel engine.

As far as I know there are no 463 diesels in Canada. There are a number of 460's. The model that is the subject of this thread was made in the years 1996->2000. It is powered by the version of the OM606 24V that also appeared in the W140 S-class. A slightly different OM606 24V was used for the 1998->1999 W210 E-class shipped to the US (and presumably Canada). The primary differences were in the EGR control system.