1997 OM606 fuel pump pressure and OFV releif pressure - PeachParts Mercedes-Benz Forum

Thomas the 97 e300d · #1 02-13-2021, 12:06 PM

I am trying to find out what p.s.i my fuel pump should put out at cranking speed and at what p.s.i should the ofv release it from my injector pump.

Diseasel300 · #2 02-13-2021, 01:04 PM

The OFV on the OM60x engines is a drilled orifice style. Pressure is generated by the volume from the lift pump acting against the orifice. When the pressure gets too high, the piston in the lift pump "floats".

Since there is no spring in the valve to regulate pressure, low pressure issues are due to air leaks or a weak/worn lift pump. Typically you should see 5-10PSI when cranking/idling. More pressure is unnecessary, anything above atmospheric is enough to fill the pumping elements and get the engine running where the pressure will rise with RPM until the lift pump piston floats.

Thomas the 97 e300d · #3 02-13-2021, 05:16 PM

I have upgraded to a OFV with a spring and wait to dissect the one on it. Am looking into what psi it should pop at so I can pretest before install but will compare p.s.i on the upgrade and the old oem but am assuming 8 p.s.i should do. I do not want any starvation of the elements at any point for performance so was thinking maybe a additional pump to assist 10 psi if not with diesel for sure with alternative fuels.

Diseasel300 · #4 02-13-2021, 08:01 PM

The factory system is more than adequate for any driving conditions. I'm not sure what you're trying to achieve here, but you can't force any extra fuel into the pumping elements by adding extra pressure. The original drilled orifice OFV will never wear out or change the flow rate through the orifice, any reduction in pressure is due to air ingress or wear/leakage in the lift pump.

The spring-operated OFV's on the 60x engines are more of a bandaid for air ingress issues or leakdown when parked. The latter is the reason I ran one in my 300SDL.