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MERCEDES 190E 2.0 Auto, fuel consumption problem

Greetings from ARGENTINA ! 4 years ago I bought an immaculate, like new 1990 Mercedes 190E 2.0 litre automatic, with only 15,000 kilometres [9320 miles] on it ! I paid a lot but then all cars in Argentine are crazily expensive. [Photos of my car are here : ]

In early 2011 the original fuel pump failed. Mileage on the car then was 38000 kilometres [23,600 miles]. The fuel pump was replaced by a local mechanic [there is no Merc mechanic where I live], but it wasn’t replaced with a mercedes original part evidently. In late 2011 that fuel pump failed and that too, along with fuel filter, was replaced this time with a Bosch pump, supposedly recommended for Mercedes Benz. This has been the only issue I have had with the car in 4 years.

But ever since the second fuel pump’s replacement, fuel consumption has gone way up. Before I always got 450 to 500 kilometers per tank of 50 litres [[280 to 310 miles per 13.2 gallons of gas / 23 miles per gallon on average].

Now my fuel consumption is such that I get only 300-350 kilometres per 50 litres of gas [ 190-220 miles per 13.2 gallons / 15 miles per gallon]. I have had the pump checked, apparently it’s installed properly. It’s been months now and I am at a loss to know what could be the cause, meanwhile I spend a lot of money on petrol [gas] which bothers me !

Any suggestions what may be the cause and / or solution ? My car now has 43,000 kilometres [26,700 miles] and still looks as good as it did in 1990 !

Thanks in advance to Click, Clack and the general community for taking the time to read and hopefully respond to my question.


RUSSELL - in San Carlos de Bariloche, Rio Negro [Patagonia], Argentina

is there a check engine light coming on?

Fuel pressure regulator?? If the fuel pressure is too high, excess fuel will be delivered…In a U.S. model, this would trigger a check engine light on the dashboard…

Does Benz have a dealer network in Argentina ? Without dealer support, it’s difficult to keep these cars operating properly…

Big Marc / Caddyman - thanks for the comments.

NO, there are no check engine lights on. There is no engine check light in fact. Just ABS, brake pads, battery, brake fluid, antifreeze, antilock brakes, airbag.

I had the fuel pressure checked by the same mechanic when I first complained that the gas consumption was high and he said all was fine.

Nearest Merc dealer to me is across the ANDES in Chile, some 300 miles from here. Buenos Aires the capital has them but that’s 1000 miles from me.

I’d get on the various MB owner forums, maybe someone there has had the same problem. You need to get connected to the biggest MB group you can find. Not many on this forum.

I spent several weeks in Neuquen, wish I had made it to Bariloche. Have you seen the TV show ‘Amazing Race’? They filmed some episodes in Bariloche. Very nice area!

I would start looking for a leak. I don’t know if a Mercedes made for the Argentine market is fuel injected or carbureted but if fuel injected, there are three fuel lines to check out and the leak would most likely be at the gas tank. The fumes from back there would be less noticeable.

If this engine has a carburetor, the fuel pump would be located on the engine. It could have an internal leak where the fuel would dump into the valve cover and dilute the oil. If you pull the dipstick, you might smell gas on it.

Since it’s a 190E, it’s fuel-injected, E stands for “einspritz”=“injected”, more or less. I think any older MB with an “E” after the model number is fuel injected.

This car should have CIS injection (my deepest condolences) on it and the first step with any performance problem on a CIS equipped car is to run the fuel pressure tests.

This requires a special gauge and special procedures. If there is someone in your area who specializes in the older BMWs or VWs (which were equipped with CIS) they might be able to sort this out because the gauge used is the same along with the general principles of operation.
Without knowing the pressures it’s impossible to say what’s going on with the car.

Thanks Gentlemen, it is fuel injected as was imported to Arg from Germany, so it’s a stock standard, good reliable ger-car, not some piece of Argentine shonk, though Arg cars made back then seem to be still on the road [aka old Ford Falcon’s by the million] whereas new ones dissappear faster than a politician’s career after caught soliciting in a public restroom :wink:

By the way Keith, Bariloche is better yet than anything that they showed in the Amazing Race !

I will get another fuel pressure test done me thinks. This time by someone else and if that’s ok go looking for a leak on the three fuel lines - maybe at the gas tank. Should this not mean there would be a puddle of gas on the floor of my garage though ? There’s never been any tell tale sign, only the smell of gas infrequently.

Cheers to all !

Anyone visiting Argentina, let me know if you head this way.


And how did you know that I am a fan of “The Amazing Race”?

The purpose of the fuel pressure test on a CIS car is not necessarily to determine if there’s a leak or not.
It’s to determine system pressure, cold control pressure, warm control pressure, and so on and make sure those are within specs.

The car should be carefully checked for any vacuum leaks because CIS systems will not tolerate vacuum leaks very well at all.

One thing you must make sure of if you have another test performed is that they have a CIS specific fuel pressure tester. The normal one will not work.

Both of the 190Es I’ve owned consistantly got 23-24 MPG, so there is definitely an issue here.

thankyou all

I don’t think your fuel pump has anything to do with the mpg problem, only coincidence. You may have a stuck open thermostat or a bad coolant temp sensor, either of which will cause the engine to run fuel-rich and reduce mpg.