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MB Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4317
Experience:  Qualified Mercedes Benz Diagnostic Technician - 20+ years experience - Workshop Foreman for Mercedes
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How do you ajust the idle speed on a 108d vito

Customer Question

how do you ajust the idle speed on a 108d vito
Submitted: 7 years ago.
Category: Mercedes
Expert:  MB Paul replied 7 years ago.
Hi Lee

does your pump have a vacuum unit on the back of the pump (see attached picture) or just a screw & lock nut?

Best regards, Paul

Customer: replied 7 years ago.

Hi Paul

It has a vacuum unit, its turned out to not be the actual pump but the injector. We've changed the injector but need to adjust the idle speed.

Any suggestions would be helpful



Expert:  MB Paul replied 7 years ago.
Hi Lee,

there are 2 different procedures depending on the type of pump & if you have the vacuum unit.

Here is the full procedure: adjustment for idle
Most of this describes linking it up to a diagnostic tester for accurate engine speed which is a Mercedes special tool.

For the actual idle speed adjustment click here: adjustment for idle pt2
You will need to use the vehicle rev counter or adjust by ear the idle speed.

I hope this is of assistance.

Best regards, Paul
Customer: replied 7 years ago.

Hithere i am the person who is doing this job for lee my name is Andy.

Engine starts to misfire when misfire occurs excessive amounts of fuel come from injecter pipe number 2 .Then the engine struggles to run and stalls .

Removed all the injecter pipes from the pump to see if we have equal amount of fuel squirting from all the outlets on the pump .

Number 2 has lots coming from it and the rest barely has any.

Then intermittantly we get an equal amount from each one and the engine runs ok then on overrun there is some diesel knock.

At one point the knock was on number 1 cylinder and lots of diesel was coming from this pipe .

In my opinion i seem to think there is a problem with the injecter pump .

Expert:  MB Paul replied 7 years ago.
Hi Andy,

I would agree - it does sound like a pump problem if it is only overfuelling on 1 cylinder.
Generally the pumps do not need much adjustment if all is working ok within the pump.

I would recommend a deisel specialist inspect & overhaul the pump if this is the case.

Best regards, Paul
Customer: replied 7 years ago.

Will try changing the pump.

Many thanks for your help


Expert:  MB Paul replied 7 years ago.
Hi Lee,

no problem, however an overhaul by a specialist may prove a lot cheaper than a replacement.

Best regards, Paul

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