ZCar Forum banner
1 - 10 of 10 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter · #1 ·
I know that there is supposed to be pressure build up in the tank but sometimes I have very high pressure, so much that it causes gas to leak at the hose connections and I think even from the top of the tank. Seems to run down from the top of the tank also, I can't see from where of course. When I open the gas lid and release the high pressure the leaking stops. Car runs fine. So every time I drive it I open the gas lid to see how much pressure is built up and some times normal, some times very high. The carbon canister has been removed and the line to it is open to air. Any Suggestions?
 

·
Registered
Joined
·
1 Posts
A car's gas tank will build pressure under normal operating conditions. High pressure in a car's gas tank may cause dangerous conditions. High gas tank pressures in a car may cause gas tank bulging, fuel line leaks, fuel pump problems, lack of fuel to the engine for combustion, dangerous conditions when opening the gas tank filler cap and potentially create fire hazards.
myfiosgateway.one




krnt.run
indigocard.ltd
 

·
Super Moderator
8 / 71 240Z, HLS30-40031, L24-052899, Sunshine Yellow
Joined
·
300 Posts
If evaporative emission controls don’t vent the gas tank, it can create a vacuum that the fuel pump can’t overcome. (Flow guide valve on the old ones) Rare occurrence but easy enough to check by running it with the gas cap off or loose.
Or in your case, a build up of pressure.
Maybe the previous owner plugged that vent line.
White Font Line Parallel Engineering
 

·
Registered
Joined
·
6 Posts
Discussion Starter · #6 ·
If evaporative emission controls don’t vent the gas tank, it can create a vacuum that the fuel pump can’t overcome. (Flow guide valve on the old ones) Rare occurrence but easy enough to check by running it with the gas cap off or loose.
Or in your case, a build up of pressure.
Maybe the previous owner plugged that vent line.
View attachment 110403
The vent line to the original canister, that was taken off, is still in the engine compartment and open to air, and I can blow into it and suck vapors from it so it doesn't seem to be plugged. It does not have a flow quide valve, it is fuel injected not carburated. I have not tried driving it with the gas cap loose but will and see if there is a difference in performance. Obviously it won't build up pressure with the cap loose. Thanks for input.
 

·
Administrator
1983 280ZX Turbo
Joined
·
2,668 Posts
The fuel tank is supposed to be pressurized so that gasoline vapors can be controlled and captured, rather than released into the atmosphere.
No, the fuel tank has a ventilation system that recycles air pressure through the engine and filtering system, and equalizes pressure in the tank and the system. If the fuel tank builds up pressure the venting system is not working!
 
1 - 10 of 10 Posts
Top