Pressure gathering in fuel tank

[Apolan]

Youll have to excuse my onslaught of tech questions, but im racing against time to finish and MOT my car as i have faculty stuff coming up.

So the problem is that te previous owner has fitted an external fuel pump, which seems to work just fine, albeit for one "small" thing. After a shorter run today the whole tank gets pressurised and i hear the pressure release line hissing under the car, desperattelly trying to get the accumulated pressure out (while also dripping gasoline). If i open the fueltank cap, gasses gush out violently.

So whats the problem? Is the pressure of the fitted pump too high? Should i just increase the size of the outlet/pressure reliefe line? On the end of that line theres a small plastic cointainer and im not sure what it really does other than let fuel/air out VERY slowly.

Thanks,
Alexander

[irishtwincam]

Let me guess, JDM SR5 carburettor car with 4AGEFI fitted?
If so your missing either the European pressure relief system (venst to atmosphere) or JDM EFI pressure relief lines from the tank (to charcoal canister).

Dangerous running without!

Get EFI fuel hardlines and possibly fuel tank pump holder/fuel level with external fittings.

[Eric]

or, dril a hole in the tank and connect a piece of hose to it wich runs to somewhere underneath the car with a valve in it., if pressure rises, valve opens and bye bye pressure.

[irishtwincam]

That was the UK AE86 evap system
Also had hole in the fuel filler neck!

[Apolan]

no the car is oem euro zenki levin its just that the fuel pump died, and since replacing that would be expensive, the previous owner fitted an external one that he had.

The evap system works, its just that it works too slowly. i wonder why the pressure rises so much in the fuel system? I could just simply remove that litlle plastic container at the end and the extra air/fuel would go out more freely?

Just wondering why this is happening?

[chenfon]

did u guy have any photo on it, because mine also facing this issue and even more serious because my model as KE70 and fit in 4AGE. so the original only have 1 fuel pipe and now modi to 2 fuel pipe (supply/return) but without any pressure release valve! can any one can show me how modify on this issue.

[chenfon]

after normal travel more that 30min, and after shutdown it able to hear that the fuel tank expand sound. and because of this cause my fuel pipe need to change (over perssure). oh, yes, i am using external fuel pump.

[Ivan141]

I am pretty used to hissing noises from the fueltank in most cars. But I get the impression it's sucking in air as opposed to blowing it out.

Stock fuel pump brackets have a small breather pipe that starts right under the lid of the pump bracket, and then goes somewhere towards the filler neck with a rubber pipe. Easy peasy to make, drill small hole, insert pipe, solder or glue in place. Then make sure it ends up somewhere where it wont make too big a mess if anything comes through.

[roman]

You might have two of the lines around the wrong way.

There's the return line that feeds fuel from the rail back to the gas tank, and this sends the fuel back into the BOTTOM of the tank, so its quiet.

The breather line for charcoal cannister comes out inside the TOP of the tank.

So if you get the two the wrong way around, your vapours will not get out of the gas tank, it will pressurise and try and push the fuel out instead.

Also the fuel return line will be noiser than it would be otherwise, as its splashing fuel out into the "air" in the tank rather than the fuel.

[chenfon]

Dear roman, can u explain in more detail and if better with drawing or photo..... i have check with my mechanic but he instead mention he install the correct way.... tq