[Benjypap]

Due to a hard start, I tested my fuel pressure using the fuel rail schrader valve. It was low; when primed the pressure jumped slightly, and then drained. Once the engine was running, pressure was steady at about 28psi. With engine turned off, pressure drained immediately. By restricting fuel flow to the engine with a clamp (and turning off the engine at the same time), I could see that pressure wasn't draining from the fuel rain, but drained straight away, and very fast, when the clamp was released.

So! I have a lack of pressure on the tank end of my fuel line. I haven't found any obvious leaks of the actual pipes, or around the fuel filter. My suspicion is that a one way valve in the fuel pump or fuel pressure regulator has stopped working, and is dropping pressure back to the tank.


My question is- Does the fuel pressure regulator act as a one way valve? Can I tell which is faulty (pump or regulator) so I can know which to replace?

Car- 2006 1.2L Twinport Corsa, returnless fuel system with regulator in the tank with the pump.

Thanks very much in advance

 

[liviu2004]

Could be broken fuel hose inside fuel tank.

 

[Benjypap]

Could be broken fuel hose inside fuel tank.

By fuel hose, do you mean one of the rubber pipes coming out of the pump and leading out of the tank?
Any idea how I'd diagnose a damaged/ perished pipe inside the tank?

 

[liviu2004]

Yes, I’ve done that before. I used osciloscope and record fuel pump current. Rotor has copper collector divided in 8 parts. I measured pump speed and current and able to find pump rotating too fast and drawing less amps then normal. Confirmed either hose broken or fuel pressure regulator. Usually it is the hose, as some people install hose which is only internal resistant to fuels and not external also.

 

[Benjypap]

After taking the seats off and unplugging the fuel line and pump power connector, I tested the pump by attempting to blow air back into it (with my mouth). The pump has a one-way valve, so it shouldn't be possible to blow air through this hole (there are 2, one is the pump, the other is the pressure regulator, which does allow air to be blown through). I could blow into the pump, so drained the tank and removed the pump. It was clearly visible that it was the hose connecting the pump to the outlet that was torn and letting fuel out, and allowing air to be blown in (liviu2004 was right). So if any of you lot have this problem, take the pump out and inspect the tubes before buying a £30 second hand fuel pump like I did