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jms
11-06-2013, 03:26 AM
Hello,

Can someone help me understand this issue?

A mechanic told me that the "fuel control assembly duty cycle" is at 100% on my 2003 Sprinter. This is causing stress on the high pressure pump. Also, there is a slight leak at the connection between the low pressure and high pressure fuel pumps.

What is the fuel control assembly? Could a leak cause the 100% duty cycle? What is the range duty cycle range?

Thank you,
Jerry S,
2003 2500 LWB

sailquik
11-06-2013, 04:33 AM
Hi Jerry S,
This is really interesting.
Was this a certified/trained Mercedes Benz Sprinter mechanic....or someone else.
If he were talking about the % engine Load (as the "duty cycle" perhaps?) then yes,
if you run low RPM a lot, (< 2400 with your 2003 OM-612 turbo diesel engine) you can
easily run the % LOD to 100%, and as long as you continue to "hammer" the engine at
less than it's intended most powerful and efficient RPM range, you will be putting some
unnecessary loading on the high pressure fuel pump, but it will easily handle pushing that
much fuel.
In fact most of the time there is some portion of the high pump's output being bled back to
the fuel tank by the pressure limiting valve in the fuel rail.
If the fuel pressure goes too high, you will get a CEL and perhaps LHM.
You need to find another mechanic (hopefully MB trained and certified for Sprinter repairs) and have
them fix the leak between the low pressure and high pressure pumps.
If you need a new rebuilt high pump, check with Dr. A (Andy Bittenbinder).
He can rebuild your existing high pump (if the core is good) to as new or better condition.
The duty cycle for a small turbo diesel depends a great deal on how the vehicle is driven and
whether or not the driver has any auxiliary performance monitoring gauge package to be able
to tell how hard the engine is really working, and taking action to reduce the % Load when it's
excessive for more than absolutely necessary.
Roger