fuel presurising
Discussion
daz the plumber said:
so what do i actualy do when i get to the canister
If it's actually connected to the plenum (some often aren't), then check the valve wiring back to earth and the ECU. It purges on certain rpm/load conditions being met (try searching for these, they have been posted on some of the emerald threads etc). If it's not connected then some other vent arrangement might have been devised (again it's been covered here more than once). If the tank isn't venting, it will prolly make some pretty alarming noises with fuel expansion contraction. Tvrjock said:
Hi Daz
Ialso tryed venting through the cap buy drilling a 1.5mm hole, but the smell off Petrol in the car especially the boot was too much, you need to remove the grill to gain access to the canister.
Graeme
On my car, the boot seal runs round the inside of the petrol cap, so drilling a small hole shouldn't fill the boot with fumes if the seal in intact?Ialso tryed venting through the cap buy drilling a 1.5mm hole, but the smell off Petrol in the car especially the boot was too much, you need to remove the grill to gain access to the canister.
Graeme
Please correct me if i'm wrong
Thanks
Matt
StreetDragster said:
Tvrjock said:
Hi Daz
Ialso tryed venting through the cap buy drilling a 1.5mm hole, but the smell off Petrol in the car especially the boot was too much, you need to remove the grill to gain access to the canister.
Graeme
On my car, the boot seal runs round the inside of the petrol cap, so drilling a small hole shouldn't fill the boot with fumes if the seal in intact?Ialso tryed venting through the cap buy drilling a 1.5mm hole, but the smell off Petrol in the car especially the boot was too much, you need to remove the grill to gain access to the canister.
Graeme
Please correct me if i'm wrong
Thanks
Matt
You are quite right but you can still smell petrol especially when the tank gets to half way and that was with a good boot seal.
Graeme
daz the plumber said:
WAS TOLD BY V8D after some tunning , the presure stays on the rail .why can`t i just change the fuel cap , i thought standard caps are self venting .
The pressure in the fuel rail? It should stay there - that's what the pressure regulator does. If they mean pressure in the return rail, it sounds more like a blockage or kink in the return. And you have had very high fuel pressure haven't you?...Non-venting of the tank would unlikely be so severe as to prevent a few drops of fuel from returning to the whole of the tank space I think.
I'm not even sure the tank cap was ever vented? Even precat Griffs don't have a vented cap - they have a breather off the filler neck, but it only goes through a roll-over valve, not a carbon/purge arrangement. The reason vented caps were not fitted to cat cars is to prevent raw fuel vapour being vented to atmosphere.
Personally I'd look to solve the problem rather than get around it by venting the fuel cap or fitting it loosely. In a roll-over / violent impact you could have fuel all over the place.
The standard fuel cap when fitted in the correct position does act as a vent. The cap is designed to turn approx 1/4 turn then lock, if you press on the top it will feel springy. The cap acts like a coolant pressure cap in reverse so when the vaccum in the tank reaches a certain pressure it draws down & vents.
It is a common mistake we see & I have seen cars where the fuel tanks are visually distorting(imploding) as a result of the cap being over-tightened
Richard
Austec Racing
It is a common mistake we see & I have seen cars where the fuel tanks are visually distorting(imploding) as a result of the cap being over-tightened
Richard
Austec Racing
Bodmin said:
The standard fuel cap when fitted in the correct position does act as a vent. The cap is designed to turn approx 1/4 turn then lock, if you press on the top it will feel springy. The cap acts like a coolant pressure cap in reverse so when the vaccum in the tank reaches a certain pressure it draws down & vents.
It is a common mistake we see & I have seen cars where the fuel tanks are visually distorting(imploding) as a result of the cap being over-tightened
Richard
Austec Racing
Richard - you explained it so much better that I did earlier.It is a common mistake we see & I have seen cars where the fuel tanks are visually distorting(imploding) as a result of the cap being over-tightened
Richard
Austec Racing
It must also be said - that if they can smell a lot of petrol then they should check their fuel pipes from the tank to the pump very carefully.
rev-erend said:
Bodmin said:
The standard fuel cap when fitted in the correct position does act as a vent. The cap is designed to turn approx 1/4 turn then lock, if you press on the top it will feel springy. The cap acts like a coolant pressure cap in reverse so when the vaccum in the tank reaches a certain pressure it draws down & vents.
It is a common mistake we see & I have seen cars where the fuel tanks are visually distorting(imploding) as a result of the cap being over-tightened
Richard
Austec Racing
Richard - you explained it so much better that I did earlier.It is a common mistake we see & I have seen cars where the fuel tanks are visually distorting(imploding) as a result of the cap being over-tightened
Richard
Austec Racing
It must also be said - that if they can smell a lot of petrol then they should check their fuel pipes from the tank to the pump very carefully.
I think I may of learnt something here re. the fuel cap. I have always just put it on and done it up tight.
Last night tank was fairly low and sat in traffic for a long time in the sun. Parked up and came back a few hours later temperature had dropped a lot. Driving off tank is occasionally thudding as it vents I assumed. Stopped for petrol and there was a serious thud as the cap came off and and I could see the tank spring out.
Looking more closely at the filler neck I can see the ident about an 1/8 turn where the cap is supposed to sit I guess, but it feels very loose and there is some slack before the spring and cork casket make contact with the neck.
So is this correct or does the cap need replacing after years of over tightening?
Last night tank was fairly low and sat in traffic for a long time in the sun. Parked up and came back a few hours later temperature had dropped a lot. Driving off tank is occasionally thudding as it vents I assumed. Stopped for petrol and there was a serious thud as the cap came off and and I could see the tank spring out.
Looking more closely at the filler neck I can see the ident about an 1/8 turn where the cap is supposed to sit I guess, but it feels very loose and there is some slack before the spring and cork casket make contact with the neck.
So is this correct or does the cap need replacing after years of over tightening?
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