Fuel Mileage Differs Between Front And Rear Tanks?

[Nitro13]

I have noticed my mileage is better when I run on the front tank as opposed to the rear. Also when removing the fuel cap on the rear tank there is always pressure that escapes,but never on the front tank. Is a vent plugged possibly,or is the fuel cap bad? Opinions,ideas?
95 Powerstroke
Superchip
3" Ddown pipe
Bullydog cold air kit

[BIG Laing]

Originally Posted by Nitro13

I have noticed my mileage is better when I run on the front tank as opposed to the rear. Also when removing the fuel cap on the rear tank there is always pressure that escapes,but never on the front tank. Is a vent plugged possibly,or is the fuel cap bad? Opinions,ideas?
95 Powerstroke
Superchip
3" Ddown pipe
Bullydog cold air kit

Are there separate fuel pumps and filters on each tank?

Have you switched the fuel caps just to see hat happens?

[Nitro13]

According to the auto parts house there is only one filter on the truck,Ill have to check out the fuel pump arrangement tomorrow. Thanks

[JSchuricht]

Don't bother. As long as you have the factory OBS setup, it's one mechanical pump in the valley along with a filter. The only other thing you have close to a filter is the screen on the pickup in the tank. That could be getting clogged and causing a MPG drop. Also check everything really carefully for leaks. You could be dumping fuel out of a return line after the selector valve.

[Nitro13]

Thanks guys for the welcome and advice.Haven't tried the fuel cap swap,but here is what I did find.I went to change the fuel filter and noticed the bowl drain ever so slightly open.After looking closer I noticed a small amount of fuel in the valley. After removing the intake(?)I checked all of the hose clamps going to and from the fuel pump and bowl and found them to ALL be loose.My other concern was the seal at the turbo. It didn't fit the land well at all,so I replaced it with another seal I had. I also noticed a light film of oil inside the turbo and manifold. I am assuming that is from the crank case breather? Is there a better way to vent the crank case? Thanks again for any feedback.

[JSchuricht]

Yep, the oil is from the CCV. It doesn't really hurt anything on a stock OBS but you'll want to reroute or filter it if you ever add a intercooler. Your options are basically to flip the cover backwards so the vent is to the rear then you can run a hose to vent it to atmosphere or filter it and return it to the intake. Here is a writeup for a SD but it's basically the same on a OBS.

[Joe0816]

Iif your ccv is leaking, replace the o rings. Mine was bad and I got mine from dieselorings.com and they work amazingly no leaks whatsoever. And for $6, the cheapest on the market.