Tech savvy: Fuel questions
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Super Member
Joined: Jun 2009
Posts: 526
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From: NYC
08 ML CDI
Tech savvy: Fuel questions
Please no stupid comments by unknowledgeable.
I was looking around the fuel rail, and havent noticed any fuel pressure regulators ( FPR) like any other german cars have . They usually go in increments from 3.0 Bar thru 4.0 and 5.0 bar... do we posses such a thing? also whats up with the fuel pump? i noticed it has 2 access doors. anybody know any technical specs on our units? FPM?
thanks in advance.
I was looking around the fuel rail, and havent noticed any fuel pressure regulators ( FPR) like any other german cars have . They usually go in increments from 3.0 Bar thru 4.0 and 5.0 bar... do we posses such a thing? also whats up with the fuel pump? i noticed it has 2 access doors. anybody know any technical specs on our units? FPM?
thanks in advance.
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Joined: Jun 2008
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From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Please no stupid comments by unknowledgeable.
I was looking around the fuel rail, and havent noticed any fuel pressure regulators ( FPR) like any other german cars have . They usually go in increments from 3.0 Bar thru 4.0 and 5.0 bar... do we posses such a thing? also whats up with the fuel pump? i noticed it has 2 access doors. anybody know any technical specs on our units? FPM?
thanks in advance.
I was looking around the fuel rail, and havent noticed any fuel pressure regulators ( FPR) like any other german cars have . They usually go in increments from 3.0 Bar thru 4.0 and 5.0 bar... do we posses such a thing? also whats up with the fuel pump? i noticed it has 2 access doors. anybody know any technical specs on our units? FPM?
thanks in advance.
Presume your car is M271 I4 engine which has Motronic?
Here are the diagrams of the fuel system. You have 2 hatches under the back seat - RHS = pump & sensor - LHS = sensor. Lines feed from LP pump to HP pump & then into the main fuel rail via a damper to the injectors. I have no idea how pressure is set on the HP pump. I'm more au fait with the fully electronic 6 cyl system. I have not included the EECS (Evaporative Emissions Control System)
Good Luck
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Joined: Jun 2008
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From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Sorry - I don't have 272 loaded at the moment - need to get it done. I'm giving you 112. All diags same for tank & lines. Only diff is fuel distributor - diag below. V6 has no HP pump. ECU controls rear pump to provide desired line pressure (measured at 14 - don't know spec). Injectors do pressurisation & metering on the fully electronic system.
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Super Moderator
Joined: Jun 2008
Posts: 19,942
Likes: 192
From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
If that is correct - it is extremely interesting. I was not aware of that. When you say regulating - Do you really mean damping line surge or really regulating a peak pressure? If it's truly regulating I will never complain about the cost of a filter again.
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Mercedes Benz Tech chiming in.. approximate fuel pressure at the rail is 55-60psi, those units on the fuel rail are accumulators, they dampen the fuel pressure pulsed from when the injectors open and close.
