Hello! I'm hoping I can find some help here on the forum to a problem I'm having with a 1979 280GE. The problem is that it's running very rich. Before I go in detail, I'll give some backround on the vehicle. It is a Euro-market 1979 280GE LWB with a manual transmission. It has the M110 engine fitted with Bosch K Jetronic fuel injection and it doesn't have an oxygen sensor. The engine is pretty young, as it only has about 60,000 kms. The main problem is that is is very smelly. Sometimes I can't travel with the windows open, as it will draw in too much fumes. Standing behind it is pretty much the same story: very smelly. Perhaps a bit like it never stopped the rich warm-up mixture even after the engine is warm... I had thought that perhaps the cold start injector wasn't working properly. I tested it, but it didn't seem to be running, so I assume there's no problem there. However, the engine runs very well, and starts as easily as my '07 VW Rabbit, regardless of the weather, or temperature of the engine. A friend and I have done a lot of research to try to figure out how to adjust the mixture. The only thing we've been able to find is what I understand to be the mixture adjustment screw for when the engine is idling, and not an overall mixture adjustment. It also seems that the Bosch K Jetronic is very sensitive to vacuum leaks. Would this cause the engine to fuel rich all the time? Any help would be appreciated!

Vacuum leaks are a priority. Are you sure its rich. I would go over all of the obvious items first. The basics like air filter,timing, spark plugs/wires, cap and rotor. Then start looking at your warm up regulator.
I think in the tech help section of this forum you will have a lot of responses from others who are knowledgable. Also the Sl forum as well may be of help since it is a European edition vehicle. If you search Warm up regulator in the SL or Tech Help area you will find a lot.
Where are you. Do you have smog inspections in your state?

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Chris
84 280sl
82 300d euro

Bailey:

All of what Chris has indicated is spot on; in addition, a check of valve clearances and of cranking compression pressures is in order. As Chris said, the basics need to be addressed first.

That said, the first injection component to check is the control pressure regulator, usually called the warm up regulator (WUR). The WUR contains an electric heating element, and if that heater has failed the control pressure will remain low, and the mixture will be rich. The WUR can be tested for heater function by first unplugging both of the cables from the ignition amplifier (aka, switchgear). Then turn the key to the ON position (not start), so that the WUR heater is powered. The body of the WUR should be noticeably warm to the touch in about 2 minutes. If the WUR does not heat, it may be suspected as one culprit, but not necessarily the only one. There are a number of different types of WUR; some have full throttle enrichment functions, and/or altitude compensation. They can be identified visually as well as by part #.

First things first, then let us know.

Thats very low mileage. I'm thinking you will need quite a bit of sorting out, as that means a lot of sitting. Any make or model of that era that has that low of mileage will need about everything gone over. Once you do it will be very nice. Anything is on the table as far as repairs. I would be looking at every aspect of that system from fuel tank to compression.
My friend bought a Camry from 1985 with 50k miles. It had to have a ton of work done. She got tired of fixing it and sold it to a friend at a loss. That friend has been driving it problem free for a long time. I guess my friend sold it after she finally got it up to snuff. Goes to show sometimes your just about done and you have to just not quit.
Your likely in it for the long haul with this one as that is really impressively low usage. How is the body? Are you up for a restoration? It may be worth it. I would be looking at everything rubber. That WUR has got to be stuck along with the rest of the fuel system. Some Fuel injection cleaner should be in order.

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Chris
84 280sl
82 300d euro

Thanks for your replies! Just to set the record straight, the vehicle has a new air and fuel filter, and "recently" changed spark plugs and spark plug wires. It did have a valve adjustment only a few thousand miles ago at the most (don't remember for sure). Some of the valves were very much out of adjustment, so it might need that done again. We have never done a compression test.

Chris: I'll take a look at the SL forums.
Also, I didn't know that they had a Camry back in 1985! Sure don't see many of those...

The vehicle is amazingly rust-free, with only small bubbling areas, and no actual rust penetration. Unusual for an old G-Wagen!

Tomorrow I will hopefully have time to check the WUR. If I do, I'll let you guys know.

I've haven't been able to test the WUR yet, because I can't figure out where it is! It seems that on some of the K-Jetronic systems, the unit is attached directly onto the fuel distributor, and then it seems like on others it is mounted remotely.

I've attached some photos of the fuel distributor / air metering assembly on the truck, and maybe you guys can tell if the WUR is actually there and I'm just missing it. I also included a photo of the production plate on the assembly in case that helps for knowing what the unit is.

Attached Thumbnails

     

Bailey:

On the M110 the WUR is located on the left side of the block, below the intake manifold, and aft of the oil filter. Follow the steel fuel line that emerges horizontally from the top center of the fuel distributor (FD). It goes to one of the two fuel connections on the WUR. The other six lines from the top of the FD go to the nozzles.

Thanks Frank. I would check now but it's downpouring at the moment... Hopefully the rain will pause for a bit tomorrow.

I was able to find the WUR with your directions (which is located just below the intake for the rearmost cylinder). I didn't know where the ignition amplifier was, so assuming that the reason for unplugging that was to protect the ignition points, I unplugged the main lead for the distributor. I then left the key in the on position for a generous 2 minutes. The WUR was as cold as a stone...

We found a PDF of how to disassemble and reassemble the WUR, but of course this requires new bits to put in it. Does anyone know where the parts to rebuild the inside can be gotten, without using another used unit for parts?

Bailey:

Before attacking the WUR, assure that power is reaching it. Pull the plug, and with the key ON check for 12V in the harness; one pin will be ground, the other 12V. Also use the ohmmeter function to check for continuity to ground of the non-powered pin. If you do have both power and ground, then use the ohmmeter to check for continuity of the heater coil in the WUR. Resistance of the heater coil: 20-40 ohms.

Old w460 Gwagen odometers turn over at 99,999 miles/kilometers

He either has 137,280 or he meant to say his engine was replaced.

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1982 300GD Carmine Red (DB3535) Cabriolet FOR SALE
1990 300SEL Smoke Silver (Parting out)
1991 350SDL Blackberry Metallic (481)

"The thing is Bob, its not that I'm lazy...its that I just don't care."

Finally got a chance to test the WUR today, and got what I consider to be some interesting results. When testing the WUR, our meter showed no resistance on the ohm setting; it pegged the meter. When testing at the plug, with the ignition on, (and with the meter on DC 50 which is the closest to a 12V setting that the unit has) there was a single brief, very small pulse, and then nothing.

This suggests to me that there's something wrong with the WUR, and also something on the vehicle end. Any ideas?

With regard to the highlighted comment, I think that things may be OK in the power supply area. Two types of fuel pump relay (FPR) were used; with timer, and without timer. The heater for the WUR is supplied through the FPR. Does the on pulse at the WUR correspond to the timed run (and shut off) of the fuel pump? Can you hear the fuel pump run for a couple of seconds when the key is turned to ON, and then shut off? If the answers to these questions are YES, and YES, then the car has a timer FPR and it is operating correctly. Power to the WUR should coincide with power to the fuel pump.

About the resistance of the WUR: are you using an analog meter with a needle over the scale, or a digital meter? Did it peg to 0 ohms, or to infinite ohms? Was the meter set to the lowest resistance scale? If a meter, either analog or digital, is set to a resistance scale above 1000 ohms, then the 20-40 ohms you are testing for will look like 0 to the meter; 40 is only 4% of 1000.

Pre-09.1981 models had FPR w/o thermal timer switch (Thermozeitschalter).
And WUR is connected in parallel to the fuel pump.

Dr. S.: Thanks!

Frank: Sorry I took so long in getting back to you. Been pretty busy...
As far as I can tell, the answers to the questions are yes and yes.

And as far as my meter, I am using an analog meter. It pegged it at 0 ohms. My meter has only 1 resistance setting labeled "OHM X1K".

Just to clarify, this is a picture of my exact meter that I'm using:
http://www.homedepot.com/catalog/productImages/400/4e/4e895dff-9270-4587-a42c-a54d7130d62b_400.jpg