ML320 please help

[Uncle Benz]

An engine is basically an air pump. The volume of air drawn through the engine depends on its speed of rotation. The throttle butterfy governs how much air can go through. If the throttle is closed, the volume of air passing is reduced and a vacuum exists in the intake manifold. When the throttle is wide open the vacuum is practically zero. If a vacuum exists at wide open throttle you are restricting the performance of your engine. This is why induction kits were invented
When I was at college my favourite lecturer swore by his vacuum gauge for diagnosing just about every possible engine fault. Proper legend. His name was Doug (oily) Wragg. Hope he is still alive.

 

[Arudge]

Don't think that can be right. Atmospheric pressure is 14.7psi which is roughly 30ins mercury so a perfect vacuum will be 30ins below atmospheric.

I had the gauge from work, which explains why it's clearly rubbish. I had no idea that perfect vacuum was one atmosphere / 30 inches of mercury. I've had a quick look on the net and the theory is beyond my understanding, i'll leave the clever stuff to the clever people.

I'll shut up now.

 

[Arudge]

His name was Doug (oily) Wragg

That's a five star name, nice one.

 

[Uncle Benz]

Vacuum doesnt draw fuel through the jets in a carburettor. A venturi is used to create a low pressure zone so the fuel is pushed through the jet by higher pressure in the float chamber

 

[LostKiwi]

This is why induction kits were invented

It's why injected engines give more power than carburettor engines.
A carburettor requires a venturi (effectively a deliberate constriction in the inlet) in order to draw fuel into the engine. Remove the restriction and increase the airflow.

 

[Uncle Benz]

That's a five star name, nice one.

He's on Linkedin!

https://uk.linkedin.com/in/douglas-wragg-6740a72a

 

[Arudge]

Vacuum doesnt draw fuel through the jets in a carburettor. A venturi is used to create a low pressure zone so the fuel is pushed through the jet by higher pressure in the float chamber

It's not the way my mind see's it but i know your right. I understand the low pressure area created in the venturi is the velocity of the air passing over the jet orifice, and i see that it's the atmospheric pressure in the float bowl pushing the fuel forward to satisfy the vacuum created. But for whatever reason i see vacuum drawing rather than pressure pushing.

My friends say i'm special (needs).

 

[benzmaester]

That ma

It's not the way my mind see's it but i know your right. I understand the low pressure area created in the venturi is the velocity of the air passing over the jet orifice, and i see that it's the atmospheric pressure in the float bowl pushing the fuel forward to satisfy the vacuum created. But for whatever reason i see vacuum drawing rather than pressure pushing.

My friends say i'm special (needs).

that makes two of us then. Just started CAT removal ready for new.

 

[benzmaester]

This forum is full of Merc genius's. Uncle Benz, bang on, Cats were blocked and new ones sorted out the problem. Thanks to everyone for their advice.
Last night I had low coolant level light come on and go out and then the oil level light came on and went out. I checked these levels and they are fine. Today, the CEL came on but the car is running well. I will check codes when I get my code reader back as mine is on loan to a "mate".
tab & thanks again.

 

[Arudge]

Excellent news. Really pleased your sorted.

 

[benzmaester]

Yes thanks Andy, so am I. I really do appreciate all the help and suggestions from you, Lost Kiwi and Uncle Benz.
ATB

 

[benzmaester]

Yes thanks Andy, so am I. I really do appreciate all the help and suggestions from you, Lost Kiwi and Uncle Benz.
ATB

Sorry forgot to say, checked codes and reset misfire codes. CEL light out and not come on again. Car runs well. Just bled brakes so stops as well now

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