Mercedes Diesel Engine Code 2631

This is another Mercedes diesel engine MBE 900 post. These engines are keeping us busy. Just when we get one code repaired another one comes along. Tonight while working on the engine in this video one of the drivers walked in to the shop and reported an engine code on his dash. It’s another MBE 900 that had been having problems with excessive smoke out the exhaust.

That’s another post to come. So I hope if you’re reading this blog on a regular basis you don’t get tired of our trials and tribulations with these engines. If I can post something that helps someone with the same problem then it’s all worth while. So let’s get into this 2631 engine code.

The 2631 engine code is by far the most frequent code of all with these MBE 900 diesel engines. It’s telling you the air intake flow is not sufficient enough. If you were to run a vacuum cleaner and something was restricting the flow or there was a leak in the hose that vacuum cleaner would not work as well.

This compares to the intake system on the diesel engine here that has a turbocharged air system puumping up to 40 psi of boost to the cylinders. From air intake to the turbo compressor through the throttle valve, EGR valve, charge air cooler into the combustion chamber there is a long way to go.

The sensors that read the air flow has a programmed spec to follow and if there is a leak or restriction in the boost system the 2631 code shows up with bells on. In the past we have found a couple of leaking charge air coolers sticking EGR valves, plugged up boost sensors and so on. It all boils down to pressure testing the air intake system and cleaning up the soot.

As pointed out in the video we will be cleaning all of the related components and pressure testing the charge air cooler. The EGR cooler is giving us some trouble at the rear connection and that’s a perfect sign that the soot build up is high in that area. I’ll be happy if that’s the case getting us closer to fixing the code.

The trouble code amber light would show up only under load climbing a grade. This is a high demand situation for maximum turbo boost to get the bus up the hill. When the bus hits the flats the code eventually goes out. At the same time the code kicks in and the engine derates which is a built in safeguard so the driver can’t go full throttle. This is a natural reaction when the engine is dying out.

So once all the work is done and the engine is back together I will report back here with an update to let you know if this plan worked. Hands on is great experience and even if you read dozens of books on the subject you still need to get your hands dirty so the experience really sinks in. Thanks for reading this post and I hope it helped you out in some way.