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Re: What should the fuel pressure be for a 750? (archive)

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Posted by Ekkehart Rackete, Bochum, Germany on December 28, 2000 at 09:54:58:

In Reply to: What should the fuel pressure be for a 750? posted by Scott Marzahl on December 27, 2000 at 16:42:34:

I have checked the TIS and found the following pressure= 3 bar. That is about 42 PSI.

The hole procedure is about 2 1/2 pages in German. I did not feel like translating all of it. It also references to some special to type test equipment only the dealers (should) have.

If you have problems getting full power you should check both pressure regulators. Check fo correct part number.

Indication: low power

- let engine idle and mesaure fuel pressure
- to simulate "full load" remove vacuum /suction hose from pressure regulator.

Pressure should rise 0.4 to 0.7 bar. Note measurements

- if pressure does not increase:
replace vacuum / suction hose and measure again

- if pressure does not increase:
replace pressure regulator

- measure fuel pressure again, note measurements
- compare value with nominal value printed on regulator housing.

If required value has not been reached the following tests have to be preformed:

If measured value is less than nominal value -0.2 bar

- cross section in fuel feed line is to small or fuel filter is clogged

- Voltage for fuel pumps is to low, due to corred connectors (wiring harness to pump)

If measured vaule is higher than nominal +0.2 bar

- stop engine, monitor pressure
- if pressure drops to nominal pressure, cross sections of fuel return line to small or line is clogged.
- check fuel line for bends

If no bends, replace return lines.

If pressure remains to high most likely the pressure regulator is defectice (sound like Catch 22)

There is more to be tested but it requires special tools. The above should be a start.
Please convert bar to psi. If I remember correctly 14psi = 1 bar. Better check.

keep me posted and I will dig up more info.

Regards Ekkehart

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