Poor mpg only doing 12mpg

[Keith270]

Hi
I have a ML270 auto it is only doing 12mpg. I have had the EGR checked and machine cleaned still no improvement. Will a Star Diagnostics show the reason for high mpg?

 

[alexanderfoti]

Not really no.

Any black smoke under acceleration? What type of driving?

 

[Keith270]

Hi
Thanks for your reply.
Are you saying no to the fact that the a Star diagnostlc will not show the reason for high mpg. As I told the Merc garage mechanic the problem and it was him that stated a Star diagnostic would show the problem. I do not want tp be paying out £150 for the test and it not show why the mpg is so high.
When I lift the bonnet there is a strong smell of Diesel.
I did a 10 mile run and my OBD Scanner said I had used point 97 of a gallon.
There is no smoke comming from the exhaust and acceleration is good.

 

[alexanderfoti]

Hi
Thanks for your reply.
Are you saying no to the fact that the a Star diagnostlc will not show the reason for high mpg. As I told the garage mechanic the problem it it was him that stated a diagnostic would show the problem. I do not want tp be paying out £150 for the test and it not show why the mpg is so high.
I did a 10 mile run and my OBD Scanner said I had used point 97 of a gallon.

Yes Star will only show fault codes that are stored, its still up to the mechanic to diagnose.

Do you have black smoke?

 

[onefortheroad]

If it's maf or oxygen sensor related , it will show on star , in live data . Have you checked all the fuel pipes for leaks and also the fuel tank and pipes . Sounds to me one of your injector return pipes or fuel filter pipes is leaking with the engine running.

 

[Keith270]

Not really no.!

Yes Star will only show fault codes that are stored, its still up to the mechanic to diagnose.

Do you have black smoke?

Any black smoke under acceleration? What type of driving?

 

[Keith270]

No smoke whatsoever from the exhaust driving steady down country road then 2 miles on dual carridge way.

 

[alexanderfoti]

Are you actually measuring the fuel economy tank to tank, or only going by an OBD readout of gallons consumed?

 

[alexanderfoti]

If it's maf or oxygen sensor related , it will show on star , in live data . Have you checked all the fuel pipes for leaks and also the fuel tank and pipes . Sounds to me one of your injector return pipes or fuel filter pipes is leaking with the engine running.

These OM612's dont' have O2 sensors and only use the maf for very rudimentary confirmation that the EGR is working, it's not used for fuelling.

 

[Wighty]

No smoke whatsoever from the exhaust driving steady down country road then 2 miles on dual carridge way.

Get onto a dual carriageway or motorway , reset the dash mpg thingy then drive for 15-20 mins at 60-70 mpg , what sort of reading do you get then .

 

[malcolm E53 AMG]

What does the temperature gauge show has the thermostat stuck open causing over fuelling?

 

[ajlsl600]

How does fuelling for cold start work on that motor. Is it stuck at cold start settings?
Has this been going on long?

 

[Keith270]

If it's maf or oxygen sensor related , it will show on star , in live data . Have you checked all the fuel pipes for leaks and also the fuel tank and pipes . Sounds to me one of your injector return pipes or fuel filter pipes is leaking with the engine running.

 

[Keith270]

If it's maf or oxygen sensor related , it will show on star , in live data . Have you checked all the fuel pipes for leaks and also the fuel tank and pipes . Sounds to me one of your injector return pipes or fuel filter pipes is leaking with the engine running.

Hi

Thank you for the reply and information. On Tuesday I will driving 30 miles to the Mercedes garage which will entail 70mph dual carriageway and then single road with 50mph speed limits. I will see what the Elm OBD11 says after journey.

As suggested I will get them to check for leaks before using the Star Diagnostic.

I will post an update after garage visit on Tuesday.

 

[Keith270]

What does the temperature gauge show has the thermostat stuck open causing over fuelling?

Hi
Temperature is showing 86 degrees

 

[KennyN]

When I lift the bonnet there is a strong smell of Diesel.

Burnt or raw ?

K

 

[onefortheroad]

Hi

Thank you for the reply and information. On Tuesday I will driving 30 miles to the Mercedes garage which will entail 70mph dual carriageway and then single road with 50mph speed limits. I will see what the Elm OBD11 says after journey.

As suggested I will get them to check for leaks before using the Star Diagnostic.

I will post an update after garage visit on Tuesday.

You'll see a Leak with the engine running . It usually sprays out , please check before driving 30 miles . If you can smell diesel, there's a reason why ... Follow the return pipes from the injectors.

 

[fabes]

OP, whereabouts are you

We may be able to recommend a good fairly local indi
A 2005 car will not benefit from going to a main dealer ( if that is who the garage is you refer to - only they charge £150 to plug STAR in!)

 

[Keith270]

No smoke whatsoever from the exhaust driving steady down country road then 2 miles on dual carridge way

OP, whereabouts are you

We may be able to recommend a good fairly local indi
A 2005 car will not benefit from going to a main dealer ( if that is who the garage is you refer to - only they charge £150 to plug STAR in!)

I live near Gantham South Lincconsire

 

[Keith270]

Hi
I live near Grantham Lincolnshire