1994 w124 estate 280 poor fuel economy

[robbieesprit]

earlier this year I had to retire my 1994 e320 due to rot through out the car after 7 years and in my use 70k miles. Not bad for a car that cost me £1500, and that made me realise that the replacement had to be another W124.
So I found a 1994 e280 estate with 150k miles on the clock. The car looked sound and original and in much better condition than the e320 it replaced and with reasonable spec.
Issues occurred with the 280 and I have to get the head gasket replaced.
The fuel gauge is not working quite as it should, and cars performance feels a little lazy for a car with 190 BHP. (although i am used to 220BHP with the e320)
I have done a recent journey totalling 300 miles in the e280, the tank was full to the brim, on return to home the yellow warning light for low petrol came on. So I filled up, again to the brim and put in a total of 56 litres.
From memory the e320 used less petrol for the same journey, am i right to suspect a issue?
The car passed mot only a month ago...
The odd thing I would say is that one of the sensors is temp sensors missing, there is a bolt in its place, there is a cable and connector available on the loom.
Any suggestions?

 

[Fastcar155]

earlier this year I had to retire my 1994 e320 due to rot through out the car after 7 years and in my use 70k miles. Not bad for a car that cost me £1500, and that made me realise that the replacement had to be another W124.
So I found a 1994 e280 estate with 150k miles on the clock. The car looked sound and original and in much better condition than the e320 it replaced and with reasonable spec.
Issues occurred with the 280 and I have to get the head gasket replaced.
The fuel gauge is not working quite as it should, and cars performance feels a little lazy for a car with 190 BHP. (although i am used to 220BHP with the e320)
I have done a recent journey totalling 300 miles in the e280, the tank was full to the brim, on return to home the yellow warning light for low petrol came on. So I filled up, again to the brim and put in a total of 56 litres.
From memory the e320 used less petrol for the same journey, am i right to suspect a issue?
The car passed mot only a month ago...
The odd thing I would say is that one of the sensors is temp sensors missing, there is a bolt in its place, there is a cable and connector available on the loom.
Any suggestions?

Hi , 24 mpg is not very good but so many problems can cause issues.

When was the car serviced and more to the point who serviced the car ?

 

[grober]

is the temperature gauge working? take out a couple of sparkplugs and check for running rich deposits

 

[GP801]

These are the official consumption figures from the brochure. City 20.8mpg, 56 mph 31.7, 75mph 25.9 assuming 4 speed auto. The 320 is on average 1mpg thirstier. On a long run ours can average 28-30 mpg but more like 24-25 in mixed everyday use.

 

[robbieesprit]

So My 300mile round trip (which I use the same roads every time) was mainly motorway/ clear roads, no urban. My E320 on exactly the same trip would achieve approximately 30 MPG.
Ive read a couple of over topics similar to this, most people report to getting close to 400mils from a tank, which would figure with my previous e320 experience, ie approximately 1/4 tank, after 300 mile round trip.
My temperature gauge reads fine on the dash, 80c on the move, rising to 85/7 in traffic.
There is a missing sensor, it is the one next to the dash temp sensor right next to thermostat housing and should sit horizontally, it was like this when I bought the car. The other sensor which goes into the side of the thermostat housing (the horizontal bigger black one) is there and connected.
Thinking about it, my first thoughts are to concentrate on sensors which tell the engine how to run. With the missing sensor above would the engine default to a rich mixture? If so, this is a relatively easy cheap fix, remove bolt, install sensor, connect up. But why would any one remove the sensor in the first place?
On my e320 this very same sensor failed, but the cause was that it failed the MOT test on emissions. My e280 is missing this sensor and passed the MOT, with good results, very odd?
Ill put this missing temp sensor in and report back...the problem is is it very hard to tell if has worked other than, do the regular 300 mile trip and come back with more fuel in the tank?

 

[johnsco]

I ran one of these W124 petrol estates around 16 years ago and I remember it being pretty thirsty for the size of the car.
As said - Check the colour of the spark plugs to check if it's running rich.
Using the car on the daily commute between Barnsley and Bradford, my fuel consumption was always disappointing.

 

[neilrr]

Anything on the roof during this expedition?

 

[grober]

Do not buy a new sensor /wire it up without knowing the purpose of the wires! Like as not the wiring room has been replaced and the spare connection has no function in your car. There were many changes to temperature sensors on the M104 over the years so blanked off connection may have no function. Has your car got air-conditioning for example? Has the existing temperature sensor two wire or four wire connections? Take a picture if you can

e.g.

Mercedes-Benz W124 Coolant Temperature Sensors Replacement | 1986-1995 E-Class | Pelican Parts DIY Maintenance Article

Getting faulty readings from your coolant temperature sensors. Replace it with help from Pelican Parts.

www.pelicanparts.com

 

[robbieesprit]

No, nothing on roof, and economy of e320 was something i lived with/ got used to, my issue is that the e280 is far worse than the e320.
Wiring loom was replaced a month ago, I ordered it using the chassis number. it arrived with the extra connector available to use.
Ill post a photo in a mo...

 

[robbieesprit]

Ok so here are the photos
The first (3588) is of the set up on my e320, and the blue coloured sensor with the right angle connector numbered 0115457128
The second (3590) is of the e280, showing bolt where blue sensor is on the e320, I am holding the unused connector, this is also a right angle and also numbered 0115457128.
The wires on the e320 set up are blue with white stripe and brown with yellow stripe
The used connector in the e280 is solid blue and solid green....

 

[pillow]

If you share your VIN I can take a look on EPC and see what exactly is listed for your car.

 

[wrdcc01]

I have the spare plug on my 280 without A/C but it is used with an extra sensor on my 220 estate with A/C

 

[grober]

I THINK THE INJECTION TEMP SENSOR IS THE ONE ON THE SIDE OF THE HOUSING? THE BLANKED OFF PORT AND SPARE CONNECTOR MAY BE FOR AIRCON- HAS YOUR NEW 280 CAR GOT AIRCON?

 

[wrdcc01]

Just read your other thread. Is your A/C compressor disengaging? Check the front disc is not rotating when the system is off. This would affect your MPG a lot.

 

[robbieesprit]

Hmmm the plot thickens...My car also has A/C but as yet I have not been able to get it working. It has had a full service and has passed as mechanically sound, but sensor/ control issues were suggested as to why it wouldnt work...the recirc button flashes on and off...
I wonder if it is related to this missing sensor...my car had the after market A/C system by Divair? Where as the e320 had MB factory AC, both are 1994 cars.
pillow has very kindly offered to look up if my car should have this sensor, so will update after christmas,
Wish you all a very merry christmas, Rob.

 

[robbieesprit]

Yes compressor is disengaging, problem is I cant get it to engage when you call for AC...

 

[wrdcc01]

Here is a wiring diagram (climate control but almost the same layout as just AC and wire colours are the same.) Factory AC does need the extra sensor.
Merry Christmas.
Dean

 

[GP801]

My 280 with working factory fit AC definitely has two sensors. (picture attached)

 

[robbieesprit]

That Sensor connector in 1894.jpeg is different to mine thats a 4 wire version, and I see there isnt the lower sensor. My set up look more like grobers photo ie with the spare 2 wire connector, but as i say without the sensor...
Perhaps I need that sensor for my AC to work, and maybe the lower one for engine management....

 

[ray_hennig]

That black 4-pole sensor at the bottom is for the engine management. The 1-pole sensor above and to the left is for the dashboard gauge and the top, 2-pole sensor is for the cooling/aircon system/aux fans.

RayH