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Matt
Matt, Engineer
Category: Mercedes
Satisfied Customers: 21725
Experience:  Mechanical Engineer with 23 years experience in the auto industry, 8 yrs in formula 1 engine testing
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I just purchased a 2003 E320. When driving sometimes feels

Customer Question

I just purchased a 2003 E320. When driving sometimes feels like it loses power briefly. It does not die are make noise and picks back up quickly. Now it is losing power when I accelerate sometimes.
JA: Is the power loss consistent, or does it fluctuate?
Customer: It fluctuates
JA: Are you fixing your E320 yourself? What have you tried so far?
Customer: I just had all the ball joints replaced by a mechanic. They drove it to see if something was wrong and it drove fine. I pu today and having problems w accelaration. I went and bought a fuelcleaner you put in the gas tank and have not used it yet
JA: Anything else you want the mechanic to know before I connect you?
Customer: No
Submitted: 9 months ago.
Category: Mercedes
Customer: replied 9 months ago.
I also wanted you to know that the check engine light is not on and no notifications of problems on dashboard.
Expert:  Matt replied 9 months ago.

Hello

I'm assuming that this is the petrol / gasoline engine

so

This sounds like a lack of fuel and could be a lack of fuel pressure from the electrical pump at the tank.

1st thing to try is to remove the fuel filler cap and then flick the ignition on whilst listening for the brief ‘buzz’ of the pump

If the connections to the pump are corroded or damaged then the pump could stop at any time or could not be running at full speed. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse,

Ideally measure the pressure at the injector rail (should usually be around 3Bar / 45psi +) and if this is low check the pump as described and also consider changing the fuel filter as if this partially blocked this too will reduce pressure.

You can also get this issue with contaminated fuel , if there’s water or dirt in the tank then either the petrol floats on top of the water or the filter sock on the pump is choked up – so if the other things check out then I’d consider pulling out the fuel pump and cleaning the filter sock

And one other thing to try is to loosen off the fuel filler cap, as there’s a 1 way valve built into the cap to let air into the tank and so prevent a vacuum from being created as the fuel leaves the tank to the engine

If this helps then replace the cap with a new item

Expert:  Matt replied 9 months ago.

Hi

do you still need help?

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