Pressure/Vac in the fuel tank

[shelldrake]

I think this is true. My canister is disconnected at the moment from the vacuum side and the tank constantly pressurises/de-pressurises...I thought at first my cannister was screwed, but it makes sense that the vac would suck it through.

[poida]

Sorry (not sorry) to rehash this topic.

Rex has a problem. At the last Track-Day he was almost booted because the AW11 seems to have developed a nasty fuel leak at the filler.

Its a hard thing to diagnose because it only happens under track/very harsh driving conditions, fuel evaporates very fast and the sheer amount that appears to be coming out.

The rubber seal at the cap is 100% intact, so before He yanks half of the system out, If the cap has a one way valve in it, what are the chances of this failing and allowing it to leak?

AND/OR..

what else should He be looking at?

Cheers Lads,

Rex

Rex, have you looked at the rubber hose that goes from the tank to the charcoal canister? I have the same problem under harsh driving conditions.

Recently a mate came past and told me my tank sounded like it was about to blow up, I went outside and it was hissing quite loudly.

I undid the cap and released the pressure. From what I can tell, the hose going to the charcoal canister is blocked and the pressure is causing fuel to leak out of my fuel cap, especially when driving excitably and on hotter days.

Cheers

[CrUZida]

Well I found that you have to SUCK the vent hose on the cannister to make nasty fumes come out, when I suck there is soft clunk (a check valve I presume?? for when some dilberry's hose is left disconnected or perishes I suppose etc ) ...so I guess its not DIRECTLY open to atmosphere after all.

Can't say for all cars, but all the ones I've looked at the check-valve is in the charcoal canister.

Unplug the line going from the tank to the charcoal canister, and it will be open to atmosphere

The line going into the tank definitely has nothing in it.

[Rex_Kelway]

Rex had a chance to investigate His problem todae.

After an Hr or so of pulling shit out and gentle pressure testing, it was discovered that the leak waaaaaaassssssssss...

The fault of the bonehead that complied the car. It turns oot that the compliance filler neck, where pressed in is not sealed around the entire circumference.

Not being redily removable Rex has tried a small amount of Devcon around the filler neck to seal the leak. Its curing now so hopefully it works...


Now another problem. Throughout the investigating Rex used a small amount of compressed air (not heaps ofcourse) to look for blockages in the system. It was done in the following locations:

(1) From the tank vent back into the tank
(2) From the vent into the charcoal cannister
(3) From the purge line to and from the cannister

But upon driving it home, it now has a frequent hunting idle. and when its not hunting its idling slightly high (approx 1200rpm)

Fuel level is very low, light on type low. He may try a full tank of go-jooce first.

Personally Rex feels He may have fucked something else in the system, He is smart.

Thoughts...

[poida]

Ah rex, the joy of fuel problems. I barely made it home last night after my automobile developed a fuel blockage and spluttered away.

I looked in the engine bay and the fuel filter looked empty…

Also I could hear my pump working overtime, trying to build pressure.

Looks like I have a blockage from the tank to the pump…

[Fish]

yeah prob got shit in the pump or dislodge something.

Also by having a vacum in the tank in kill stop the engine from running and damage pumps!

This is quite noticable in plastic tanks. My daihatsu does it ( makes the hissing noise which is air rushing in).

I use 8mm line to vent my tank and that goes down behind the rear wheel in the race car. also helps if i roll. it stops the fuel coming out. but it does need to be a bit bigger. the cap is a bugger to get off after 8 laps.