[MSGGrunt]

1985 280CE.

At right around 2,000 RPM the car is losing power. Doesn't matter if the motor is hot or cold.

Items already replaced are:

• Fuel Pump
• Fuel Filter
• Frequency Control Valve
• Fuel pump Relay

Fuel pressure is good.

Any suggestions?

Vacuum leak maybe?

 

[Nutz 4 Benz]

Have you ever adjusted the valves? Power and vacuum line solid on WUR? Resistance of green wire from distributor to ICU within spec?

 

[MSGGrunt]

It isn't in my possession. The seller is trying to sort it out before shipping it and his mechanic is not a MB specialist.

 

[MSGGrunt]

What is the resistance supposed to be from the coil to ECU? I have heard the combination of resister plugs and resistor wires can be an issue as well as well as a bad coil. The car has sat for a good amount of time without being driven, but still only 43,000 miles.

 

[Nutz 4 Benz]

I’d first lean towards vacuum line somewhere not tight or loose. Also vacuum line to fuel pressure regulator off wye boot has to be leak free to enrich on acceleration or it will be gutless.

What about the coil?

 

[MSGGrunt]

WYE?

 

[Nutz 4 Benz]

“Y”

The big hose in photo. Very important this hose is tight and connected to fuel pressure regulator via the nipple also tightly.

Also possible the fuel distributor plunger could be bound up. Pull fuel pump relay and start car and run until it dies. Press down the metering plate all the way down and release. It should then return to the top rest position. Replace fuel pump relay and turn key to on to pressurize the system. Push down on metering plate and see if it raises to the rest position. do this only one time or the engine will flood with gasoline

 

[Nutz 4 Benz]

Also since it sat for so long, maybe the intank filter screen could be plugged with rust limiting fuel delivery.

 

[MSGGrunt]

Tank has been flushed and new fuel pump and filter installed, not saying the screen couldn't still be clogged.

 

[MSGGrunt]

Now that I finally have the car in my possession it is much worse than losing power at 2,000 RPM. The car will start immediately, but acts like only two or three cylinders are firing (M110 6-cylinder gas) and quickly dies, won't even idle. It seems like it is getting too much fuel, but I have no confirmation of this. Any chance the diaphragm inside the fuel distribution block would cause this sort of issue? I've read where age and ethanol fuel kills them.

Somebody may have had this off before as the hose clamps don't look OEM and there is a nut missing on one of the hold down bolts.

 

[tsharkey]

Have you watched this as it may provide some insights

 

[MSGGrunt]

That was insightful.

I have confirmed, I believe, that the fuel distribution block has been changed. According to Bosch the part number for a 1985 280CE from 03-1984 to 08-1981 should be 0-438-121-020 and the one in my car is part number 0-438-121-115, which would correspond to a 280CE dated 03-1977 to 08-1981. I will have to look and see what the numbers are on my 1978 M110. The previous owner said it was running and driving great up until recently, but.... I guess it wouldn't hurt to check the block and head casting numbers. I was told that the block was replaced by a new short block from Adsit and the original head put on that block. I do have the receipt for the install. I'll also be curious what a simple compression test shows.

 

[Nutz 4 Benz]

What you have there is the airflow sensor with frequency valve or otherwise known as K Jetronic lambda. You should have a ‘brain’, O2 sensor and the frequency valve. The 3mm screw should be turned until a duty cycle of 45° on the 4 cylinder scale of a dwell meter.

This system more or less is the grandfather of the later KE Jetronic.

 

[FratBoy]

I have a couple of extra M110 ECU “brains” around if that’s the issue. But it seems they rarely fail.
FB

 

[garyd75]

Check cis lines under the intake manifold

 

[MSGGrunt]

I am not sure if I want to delve into it myself or leave it to someone who knows this system a lot better than me to diagnose. I have a 1978 280E that I could swap ECUs with or even swap the entire K Jet fuel injection system, but I am not sure this would be going overboard or not.

 

[MSGGrunt]

The problem was looked into by the sellers mechanic prior to my purchase and I would assume the simple things like timing, fuel pressure, etc... were looked into. But, he was not a Mercedes specialist or probably very familiar with the K jetronic system.

 

[MSGGrunt]

In my post above about the part number, I pulled the wrong number off the air-flow box and not the fuel distributor. The correct number for the fuel distribution unit is
0 438 100 069. I just ordered a kit from https://salvox.com/

I figure it can't hurt.

 

[tsharkey]

The reality is there are less and less mechanics knowledgeable about these systems given the age the bespoke nature. I have found that I need to learn as much as I can to keep up the maintenance and good working order of my jalopies. I see Kent has manuals / videos on these as well - A lot of my 1st up learning on the OM617 and related systems was from him.

That said, their may be a Bosch injection specialist in your area as not just MB used these systems. ​

 

[MSGGrunt]

I like learning and figuring out things on my own, but in this case I have decided to put the car in the hands of an expert. I found a specialist in close to Boston, European Auto Solutions, that has two mechanics that are well versed in these older fuel injection systems. I visited there shop and the number of high end older Mercedes, Porsches, BMWs, etc was staggering.

European Auto Solutions Mercedes-Benz & BMW Repair Specialists

European Auto Solutions in Waltham, Massachusetts specializes in repair and maintenance of BMW & Mercedes-Benz autos in the Boston Metrowest area and beyond.

www.virtualeas.com

I did pull the plugs and did a compression test and the compression was fine. The plugs, NGK BP6ES, are a different story. They are as black as can be. I would say at least part of the reason the car is running very poorly would be over fueling??? The plugs alone wouldn't cause that big of an issue I would think, but I sourced the correct Bosch plugs from Germany just in case.

What would cause and over fueling situation? The fuel distributor kit arrived, but I will let the experts rebuild it that way I know it is adjusted properly.