Hi,
I got a new fuel pressure gauge and checked the fuel rail pressure on my 1997 Volvo S40 2.0 petrol (200K miles). This is a normally aspirated engine, not the one available in US.
First I released the pressure from the rail before fitting the gauge. Then I turned the key on ignition II to build up pressure in the rail (did that several times so that the rail gets full). The reading are then as follow:
- Turning the key on ignition II (engine not started): pressure spikes up to about 40 PSI while the fuel pump makes its noise (it has always done that, even the previous pump did that). As soon as the fuel pump noise goes away, fuel pressure drops down to 31 PSI and stay there.
- When starting the engine, with engine idling, the pressure goes up to 38PSI. Raising the RPM makes the pressure go up to about 40-45PSI but when idling it goes back to 38 PSI.
- After shutting off the engine and waiting for 20 minutes, the rail keeps a pressure of 23 PSI. VADIS mentions that during a 20 min period, the fuel pressure shouldn't go below 29PSI but they start from about 45 PSI idling while mine was only 31 PSI...
OK I don't have particular trouble with the car but it has always felt a little sluggish. I have no idea if these fuel pressure reading may be an explanation here. Since the pressure drops by about 8 PSI in a 20 min period, I don't think the fuel regulator is leaking. However I don't understand why the pressure spikes up to 40 PSI while the fuel pump is making the noise and then goes down suddenly to 31 PSI and stay there. Where does these 9 PSI go??? Is this an issue with a return valve somewhere...or still an issue with the fuel pressure regulator?
Thanks for any input!
PS: forgot to mention the fuel filter was renewed 6K miles ago and the fuel pump has 130K miles on it.
I got a new fuel pressure gauge and checked the fuel rail pressure on my 1997 Volvo S40 2.0 petrol (200K miles). This is a normally aspirated engine, not the one available in US.
First I released the pressure from the rail before fitting the gauge. Then I turned the key on ignition II to build up pressure in the rail (did that several times so that the rail gets full). The reading are then as follow:
- Turning the key on ignition II (engine not started): pressure spikes up to about 40 PSI while the fuel pump makes its noise (it has always done that, even the previous pump did that). As soon as the fuel pump noise goes away, fuel pressure drops down to 31 PSI and stay there.
- When starting the engine, with engine idling, the pressure goes up to 38PSI. Raising the RPM makes the pressure go up to about 40-45PSI but when idling it goes back to 38 PSI.
- After shutting off the engine and waiting for 20 minutes, the rail keeps a pressure of 23 PSI. VADIS mentions that during a 20 min period, the fuel pressure shouldn't go below 29PSI but they start from about 45 PSI idling while mine was only 31 PSI...
OK I don't have particular trouble with the car but it has always felt a little sluggish. I have no idea if these fuel pressure reading may be an explanation here. Since the pressure drops by about 8 PSI in a 20 min period, I don't think the fuel regulator is leaking. However I don't understand why the pressure spikes up to 40 PSI while the fuel pump is making the noise and then goes down suddenly to 31 PSI and stay there. Where does these 9 PSI go??? Is this an issue with a return valve somewhere...or still an issue with the fuel pressure regulator?
Thanks for any input!
PS: forgot to mention the fuel filter was renewed 6K miles ago and the fuel pump has 130K miles on it.
Last edited: