high pressure fuel tank - Car Troubleshooting


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haze386
User

Oct 23, 2006, 3:26 AM

Post #1 of 3 (1471 views)

high pressure fuel tank	Sign In

Hi. I have a 2003 Nissan X-trail (a light suv like cr-v). I uses 95-octane gasoline. When i open the fuel tank cap after about an hour of driving, a stream of high pressure air comes out. I'm a little bit worried, because I don't know if it is a problem. Can anyone help me please.

Thanks

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Oct 23, 2006, 3:52 AM

Post #2 of 3 (1468 views)

Re: high pressure fuel tank	Sign In

Hmm?? Most cars do not require 95 octane and that's your choice but it is not the cause of this problem.

There may be a problem with the vapor recovery system and a little bit of pressure or vacuum could be normal but NOT a lot, T

DanD
Veteran / Moderator
DanD profile image

Oct 23, 2006, 3:56 AM

Post #3 of 3 (1468 views)

Re: high pressure fuel tank	Sign In

I believe you’ll find that this is normal for today’s vehicles. They have a system called “enhanced evaporative emissions” and do not vent fuel system’s fumes to the atmosphere. These fumes are contained and monitored by the computer; when the criteria is meet the computer opens a purge valve and the engine draws these fumes in to be burnt.
Why the pressure builds is that a much larger amount of fuel is delivered to the engines fuel rail (injectors) then what is required to run the engine. This acts like a reserve incase you suddenly jump on the throttle; the fuel is there waiting to be used.
But while cruising (light engine load) this extra fuel is sent back to the tank via return lines. The heating (expansion) of the fuel from being under the hood and the small amount of pressure in the return system ends up back in the tank. That’s until you remove the gas cap or the computer decides to purge the system.
I’ve left a lot out in the explanation of the system but hope I got the idea of why across?
Dan.

Canadian "EH"

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