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Hey everyone, I need a little help on what looks to be a fuel pressure problem. I have Megasquirt, but I'm thinking this is either a fuel pump or pressure regulator issue. I have a fuel pressure gauge on the fuel line before the fuel flows to the fuel rail. I seem to recall it's always read around 37psi, but I thought I'd check things out because my engine sounds like it's missing a cylinder (note: leakdown test sais everything is ok).

A week ago when it started to run poorly I noticed the fuel pressure at idle was down around 32psi. Later it was at 37psi so I wrote off fuel pressure as an issue.

This weekend the engine was running worse so I looked at fuel pressure again. At idle its 37 psi, but if I blip the throttle the fuel pressure drops down to 32 psi.

This isn't normal, right? Fuel pump or fuel pressure regulator?

Thanks,
Bill

It used to be 37psi always?
That sounds really wrong to me, don't you have a vacuum line to your fuel pressure regulator? The pressure differential across the injector should be constant and therefore the fuel pressure will follow plenum pressure, i.e. fluctuate quite a bit.

OK, you got me on that one. I guess whenever I looked, it was 37psi. I never did the blip the throttle test though.

Can I interpret your response to mean the phenomena that I'm seeing is normal?

Thanks,
Bill in Maryland.