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Matt, Mechanical Engineer
Category: Mercedes
Satisfied Customers: 22901
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a 2003 sprinter van. When cold it goes well, when warm

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I have a 2003 sprinter van. When cold it goes well, when warm it wont rev very high and loses power.Shows fault of low boost pressure. Fitted new waste gate activator switch and new turbo, with new pressure sensor.Replaced split pressure hose and turbo pipe. fault still showing, says turbo no good. Any ideas?
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sounds like you've changed fair bit already

Also check that the vacuum hose running to the dump / turbo bypass valve is intact with no leaks as if the dump valve is opening prematurely you'll be losing all your boost

If this is OK then remove the high pressure intake hose after the turbo and have a feel of the turbine wheel - there should be no play radially at all - but a little bit of axial / end to end float is normal

one other possibility is that the wastegate actuator spring has gone soft so allowing the wastegate to open prematurely - if your actuator has a threaded end you can increase the preload on it to see if this improves things otherwise these units are quite cheap compared to a new turbo so it may be worth trying a replacement

Matt, Mechanical Engineer
Category: Mercedes
Satisfied Customers: 22901
Experience: BEng hons Mech engineering, in auto industry 22 years
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Customer: replied 2 years ago.

New actuator switch and hoses replaced onto new waste gate. New pressure pipe after turbo fitted. Pressure sensor replaced. Appears to be no leakage from pressure hose assembly.Someone suggested that it could be the high pressure valve on fuel pump.What do you think? I have drilled a hole in fuel cap just in case there was a vacuum. Not driven since doing that. Thinking of checking fuel filter to see if it is leaking air.


its well worth checking the fuel filter housing as they can crack and draw in air as you say

and not enough fuel will result in low boost

so if the fuel cap modificaiton doesn't work then I'd suggest measuring fuel pressure at the injectors

as this will show if the main pump is Ok and if you're getting any air drawn in

do you still need help ?