Poor Mileage
12-04-2003, 01:13 PM
#16
Race Car
Thread Starter
36-38psi at an idle is not enough to kill my mileage? Those emissions readings were before the O2 sensor was changed as well, but my mileage got worse after that. I have pulled both vacuum lines, no fuel, so they are not broken. My fuel pressure only changes 4 psi when I unhook the vacuum line (36-38 to 40-42), I think my FPR is bad because of this.
The leakdown test on the fuel rail. I noticed, after 20 mins, it should be down to 14psi. What lets the pressure out? The way I understand it, the FPR opens gradually, starting before 28psi (where it should be at an idle), so once the engine is shut off, it still allows some fuel past it until the pressure comes down. Since mine only drops 4 psi over 20 mins, that makes me think that perhaps my FPR is stuck just shy of closed.
I don't know what to check next, but if my fuel pressure isn't the cause of my mileage, then I don't want to blow 100 bucks on the FPR.
I know my compression numbers are WAAAY down, I have 125psi on my best cylinder, 115 on the worst, would this cause such bad mileage? Or perhaps it's a combination of the two.
The leakdown test on the fuel rail. I noticed, after 20 mins, it should be down to 14psi. What lets the pressure out? The way I understand it, the FPR opens gradually, starting before 28psi (where it should be at an idle), so once the engine is shut off, it still allows some fuel past it until the pressure comes down. Since mine only drops 4 psi over 20 mins, that makes me think that perhaps my FPR is stuck just shy of closed.
I don't know what to check next, but if my fuel pressure isn't the cause of my mileage, then I don't want to blow 100 bucks on the FPR.
I know my compression numbers are WAAAY down, I have 125psi on my best cylinder, 115 on the worst, would this cause such bad mileage? Or perhaps it's a combination of the two.
