The search continues.. odd fuel pressure behavior

[plethaus]

I'm still trying to track down the cause of my lean condition (172/176/136 codes). I have a fuel pressure gauge and I've got it hooked up to the schrader valve on the fuel rail.

With KOEO, I hear the pump prime, then the pressure spikes to 20 for a second or two then drops to zero. If I remember correctly it is supposed to maintain a steady pressure with KOEO, something like 28-32psi. So my car seems to be doing something wrong, but I can't remember the thread where it had the info on the fuel pressure behavior.

When I start the car it idles at about 32 psi and a WOT blip reads about 38psi.

Is this normal or is there something amiss here?

 

[projectSHO89]

You should have 40 psi at prime. When vacuum is applied to the fuel pressure regulator, the pressure should drop to around 32 psi and stay relatively constant.

 

[plethaus]

You should have 40 psi at prime. When vacuum is applied to the fuel pressure regulator, the pressure should drop to around 32 psi and stay relatively constant.

Does the 40psi at prime stay at 40psi or only when you can hear the pump prime? In other words is it SUPPOSED to drop immediately back to 0psi?

Also what do you mean by "when vacuum is applied to the FPR"? Sorry, I'm a noob when it comes to fuel systems. Are you saying it should be 32 psi with engine on running at idle?

 

[ohfosho]

it should not hit 0 psi besides a few minutes of sitting, if not hours...

you could have a bad connection where you are hooking up, or there must be a leak in the system. injector rebuild time? or also likely check valve maybe.

 

[plethaus]

it should not hit 0 psi besides a few minutes of sitting, if not hours...

you could have a bad connection where you are hooking up, or there must be a leak in the system. injector rebuild time? or also likely check valve maybe.

It could be a bad connection where I'm hooking up.. the rubber seal inside the gauge's connection came apart when I disconnected it last night.

Where is the check valve and what exactly does it do? How will the car run if it is bad?

 

[CerberuS]

fuel pressure , is something that supposed to have constant pressure.

the 20 to 0 is NOT normal , id suspect 2 things ,

bad pump .
bad chack valve.

And i doupt the wires/connections has anything to do with this.