NegroC230

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.

Glyn M Ruck

Don't be cheeky

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

NegroC230

thanks, very informative, however ..i am 2.5L v6...m272?

ps: what is number 55 on the last picture? right next to the injector

Glyn M Ruck

Damper

NegroC230

i noticed to have the sameunit on my rail too....but its too small to be looking like the FPR i was mentioning not to mention it doesnt have a vacuum port on it.

Glyn M Ruck

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.

p_gill

I don't have a nice diagram to share but the regulator is built into the fuel filter.

That's why the filter has so many connections.

Good luck

Paul

Glyn M Ruck

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.

splinter

<---not tech savvy.

Specification is ~3.8 bar.
p_gill is correct.

Glyn M Ruck

Thanks John - I learned something today - that's good - Savvy

NegroC230

thats what i call German Engineering, LOL

derffred

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.

bumpnzx3

no wonder a filter costs as much as it does.