Volvo EFI question

[Albe]

Hi guys. I got a 96 Volvo 5.7 Gi. I'm trying to test the fuel pressure in the TBI. Got the gauge today. The manual wont give me the numbers I should see at idle and at WOT. I'm getting some RPM hesistation after 4000 RPMs. The fuel pressure diaphram might be bad. The scan tool shows no problems with all the sensors. If someone can share the numbers it would help me troubleshoot. The book says I should see 9-13 with engine not running. That's all it mentions. Thanks.

 

[snapperbait]

Re: Volvo EFI question

The fuel pressure should be 9-13 lbs of pressure with the ignition switched on, just as the manual says.. <br /><br /> The fuel pump is electric and does not increase or decrease pressure as engine speed changes although you may see a very slight pressure drop durring accelleration (1 psi?) at higher RPMs, but it should still be in the 9-13 psi range...<br /><br />Timing set to spec, and advancing properly?<br /><br />Dirty Injectors are a likely culprit..

 

[Albe]

Re: Volvo EFI question

I got 16 psi on the fuel line from the separator tank to the TBI while the engine was running at idle. On top of separator tank, there is another fuel pressure point, which gave me 11 while at idle. <br /><br />With just the ignition switched on, the pressure would not hold (goes back to zero) after a few seconds. I could not tell what the pressure was, but it was not holding. I found a tiny leak on the connection to the high pressure fuel pump (damage O-ring). I will try to fix that first.<br /><br />I found some fuel on the vacum rubber line that goes from the separator tank to the TBI. I don't know how the fuel got there. Anything else I can check?

 

[Albe]

Re: Volvo EFI question

I need help.

 

[snapperbait]

Re: Volvo EFI question

Albe, are you having any trouble with fuel-fouled spark plugs? The reason I ask is because the 16psi on the line to the TBI is too high and should be in the 9-13psi range with 11-12psi being the sweet spot... <br /><br /> Have you replaced the leaking o-ring and re-tested the fuel psi?<br /><br />If everythings is still the same you may have something causing a restriction in the smaller fuel return line from the TBI... If thats not the case, then you may need to replace the fuel pressure regulator...<br /><br />It's not unheard of to have some fuel on the vacuum line but I would replace it incase it has a small leak...<br /><br />The pressure does not hold with the switched ignition on because there is a bypass port in the TBI, so when the pump initaly cycles when you turn the key on, the pressure comes up then when the pump shuts off the pressure is relieved by the bypass port... Thats normal..

 

[Albe]

Re: Volvo EFI question

Snapper,<br /><br />Thanks. I did fix the leak. The fuel psi is still at 16 on the high pressure side. I called Volvo today and the tech guy is pretty much align with you. I cant think of any restrictions on the return line. I will check tommorrow. The other problem he mention could be the vapor separator. He faxed me some info on how to troubleshoot all this. Lets see. More to follow. Thanks again,<br /><br />Albe