Is it my imagination or is it easier to start and faster acceleration with full tank?

[Jack Lope]

It seems that the truck starts much quicker and possibly accelerates faster when the tank is topped off. Is this my imagination? Anyone ever experience similar?

 

[Assel]

maybe your tank breather is clogged? when it gets emptier it creates a vacuum and the Lift Pump (probably some worn Seals etc.) has to work harder and you loose the Fuel there?

when you drive the tank empty does it make "shhhhhhh" when you open the cap? ...

we have a wheel loader at work , when I drive this for ~10 hours I need both hands to remove the Fuel-tank cap. Huge Vacuum there ...but they tried new Caps, cleaning etc. it still "PHSHSHSSHSSSHSHSHHHHH" like 5-7 seconds when you open the cap... and you cant just pull it off, it sits so hard you need to wait until the Tank is filled with Air ...

 

[98G]

maybe your tank breather is clogged? when it gets emptier it creates a vacuum and the Lift Pump (probably some worn Seals etc.) has to work harder and you loose the Fuel there?

when you drive the tank empty does it make "shhhhhhh" when you open the cap? ...

we have a wheel loader at work , when I drive this for ~10 hours I need both hands to remove the Fuel-tank cap. Huge Vacuum there ...but they tried new Caps, cleaning etc. it still "PHSHSHSSHSSSHSHSHHHHH" like 5-7 seconds when you open the cap... and you cant just pull it off, it sits so hard you need to wait until the Tank is filled with Air ...

Post office vehicles used to collapse the fuel tanks that way...

 

[dependable]

Also might want to check lift pump output.

 

[Jack Lope]

Thanks for the replies.

When I first got the truck, it used to spew diesel all over the place, coming from what looked like the top, front of the engine. After driving it a couple times, it stopped spewing. The guy I got the truck from gave me a couple O-rings that was supposed to be the fix for the leak. I still have those o-rings around somewhere.

Now-a-days, occasionally a little diesel seems to leak. I can see the stain on the drive way closer to the passenger side of the truck.

I thought I'd add that info just in case it was relevant. I'll check into what has been suggested.

 

[dependable]

If it is coming from the fuel filter base, you may have the classic leaky pressure sensor. If it is front of engine, check the small weep hole in the lift pump. If it is leaking there you need new pump, also check oil, as it can mix fuel in with motor oil when lift pump diaphragm goes.

 

[cpf240]

My guess would be the throttle shaft seals were / are leaking, which usually runs down the valley and out the drain hole at the bottom of the bell housing. I don't see how this would be affected by the fuel level in the tank, so I'd look to a vent issue for the full tank vs almost empty tank differences you are seeing.

 

[Matt Kahle]

I really don't see how it could be starting faster. Remember the engine has a injector pump..... I would think if it were leaking the truck would be running different. Awhile back my truck needed to have the fuel system bled, and the RPMs were a little jumpy.