Resolved Fuel Pressure Problem

[Xit40]

I'm having a fuel pressure problem. It originally started when I put some 100 octane race gas in from the local Sunoco (as far as I can tell). My fuel pressure never goes above 38-39 psi. I'm currently running a Fuel Lab AFPR with a liquid filled pressure gauge. It gets up to 38-39 psi without out a problem, but after that you could turn the adjuster screw all the way in and nothing happens. This happens with both the original FPR and the Fuel Lab AFPR so it doesn't seem to be a regulator problem. I originally figured maybe my fuel filter was clogged so I changed that out earlier today, what fun that was, with no joy. I have a MKIV fuel pump that's less than 2 years old in my car and the fuel pump has been rewired. I've checked the lines in the engine bay and fuel is not leaking out anywhere in there. I plan on taking the fuel pump out tomorrow and checking it out. What else could be causing the problem? Fuel Pump O-ring? I'm kind of at a loss. I found a thread about clamping fuel lines off to check for a pressure loss so if nothing seems amiss with the pump I'll try that. Any advice would be greatly appreciated.

 

[viprez586]

I'd take apart the FPR and clean it. Sounds like the diaphragm is stuck or leaking.

 

[Xit40]

The problem was the same with both the original stock FPR and the Fuel Lab AFPR. It is bleeding the fuel pressure off within 10 seconds. So I doubt the problem lies with the regulator.

Other than a leak somewhere, which I am going to check for right now, what would cause the pressure to bleed off so rapidly?

EDIT: I just finished clamping off the rubber lines in the fuel system. First I activated the fuel pump and then clamped off the feed line from the fuel filter to the fuel rail. It held pressure with no problems. I then moved back to the fuel pump, activated the fuel pump again then clamped off that hose and again it held pressure no problem. So my lines are not the problem. Where do I go from here? The problem is clearly behind the rear rubber line that hooks into the hard line at the tank. What kinda possible problem am I looking at?

 

[viprez586]

Your edit makes it sound like an injector is hanging open and bleeding off pressure.

It should hold residual pressure for a while. Having extended crank issues hey?

I'd check all lines and connections, make sure nothing is leaking though. If no leaks are evident, look at the rail and injectors for it bleeding off somewhere.


I'm not sure on the 2Gs but there may be a fuel pump check valve, or a check valve in-line somewhere. Typically they're built into fuel pumps/assemblies. That would be a suspect.

 

[612 Performance]

Have you tried taking fuel pressure readings in different areas of the line that way you can tell if it's an issue with the fuel pump or if the fuel is bleeding off somewhere

 

[Xit40]

Please mark as resolved.

The issue was the fuel pump o-ring. The clamp on the fuel pump came loose somehow and the o-ring slide down and it wasn't sealing as it should have. I pushed it back up in there, made sure it was flush and clamped it down tight. It's not going anywhere now. Problem solved. I can now set my fuel pressure as high as I want.