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quick fuel pressure question??

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Is it possible when analysing a log of your fuel pressure that you could may well be reading air pressure as well as fuel pressure?

Is it possible for the fuel pump if it was too Serge to pump air or not really?

just curious as somebody brought this up to me the other day and it got me thinking?

anyone?

The sensor will measure the pressure of fuel, or fuel with air. It is unlikely that the fuel pump can pump compressible air at the same pressure as incompressible fuel -- so if the pump is attempting to pump air, you would expect to see the measured pressure drop.

A similar situation is If a pump inlet is restricted, then the pump will sometimes cavitate (introducing air) and won't be able to maintain the volume of fuel required to keep the pressure stable.

This isn't a direct answer to your question, but if you are chasing a problem that seems like the system is not delivering enough fuel even though the fuel pressure sensor readings look OK, it's not a bad idea to have the fuel injectors removed and cleaned. A clogged fuel injector won't cause a low fuel pressure reading, it simply won't allow the correct amount of fuel into the engine. Symptoms of this would be good fuel pressure readings but the engine needs abnormally high fuel pulsewidths to hit desired Lambda targets, or the engine seems to 'run out of injector' without making as much power as those fuel injectors should support.