Where's the fuel leaking from?

[Adrian]

After not using the car for a couple of weeks I started it up and straight away got a strong smell of petrol coming through the air vents. I reversed back in the garage to take a look under the bonnet but couldn't see or smell anything there. But round the back of the car on the floor was a small patch of petrol. Obviously a leak in one of the pipes to the pump I though. So I left it to look at today.

Now today under the car I can't see any sign of a leak anywhere! The way it puddled on the floor I thought it'd be easy to spot. I've run the engine, squeezed all the rubber pipes and given everything a good wiggle but it's all sound and not a hint of a leak anywhere. The pipes don't look perished and I'm not particularly inclined to replace them if they're not really the problem.

Is there anywhere else that it could be coming form back there? The pipes going to the top of the tank are hidden from view but there's no sign of staining anywhere. It all seems to be OK now, like it was a temporary excess of fuel somewhere... but that doesn't make sense. A couple of months ago I got a smell of fuel after a short journey that had me puzzled but I ignored it and it went away - until now.

[Paddy]

I have the same problem, it smells really bad and when i looked under the car at the back i could see petrol dripping from the tank, i am told that the seam on the tank perishes. Not good me thinks as the tank will have to come off :frown:

[nigescalli]

most common probs on them are the 2 metal pipes that go in to cap on top of the tank

[Adrian]

I take it the only way to check the pipes is to drop the fuel tank? That would be a bit of a bugger.

[Adrian]

This has got me completely puzzled now. I've "hot-wired" the fuel pump so I can have it running with the engine off. I figured this ought to pressurise both the supply and return lines to the max. So underneath the car, with the pump running, I've worked all the hoses I can get at and there's no sign of a leak on any of them whatsoever. How can there be an intermittent leak like this?

[Robert_Dale]

it defo NOT fromt he engine bay?? normally the rubber hoses perish or split runing next to your fuel rail!!

if it came through your air vents i would definately say its a rubber hose going in the engine bay!! happened to my 8valve!

they are hard to spot (mine wasn't cos it was p*ssing out lol)

[Adrian]

No, but I'm stating to doubt my own senses now... I'm sure I dipped my finger in the small wet patch on the garage floor behind the rear wheel and it smelt of petrol. I'll murder the damn cat if it wasn't. Wifey's Nova sprung a leak in just about every rubber fuel hose over the last year so I'm pretty adept at spotting and fixing these things - but mine's got me really scratching my head now.

Usually the rubber perishes around the edge of the fixing clips or goes "crazed" - either way a good squeeze makes a tiny wet patch apear on the hose (if it's even that hard to spot). But all my pipes seem to be in good shape (even though they're 12 years old). If the cat wasn't the cause of the puddle (and I wasn't mistaken about it smelling of petrol) then I can't see how so much could have hit the ground yet refuse to show up the next day under close inspection.

[Leigh]

I was just gonna say the same as Robert, mine came apart at the jubilee clip on the return line in the engine, started driving to work with 1/2 tank (only 3 or 4 miles trip), everytime I stopped at a junction I could see the needle dropping! Thought at first it was just the usual 'sloshing around' effect, until it visibly started going in front of my eyes, then I put the blower on to clear the screen and got a nice eau de Optimax air freshner..
All it took to fix it was another jubilee clip, but cost me nearly £20 worth of juice! grrr

[Adrian]

Now I'm thinking about this from another angle... The car was sat in my garage for 2 weeks - when it was stinking hot. It gets particularly hot in there because it's got a slate roof which really soaks up the sun. Could it be that the ambient heat built up a lot of pressure in the fuel tank... there's a fairly complcated venting system IIRC, with a valve that opens when the engine is started. Perhaps the leak is on this side somehow?

It's totally refusing to show any signs of a leak now and I've been fiddling around looking at it all day!

[Fraz]

how much fuel do you reckon was in the tank??

[Adrian]

Exaclty half full on the gauge Fraz.

[v6calibra]

wabble the in let and return pipes in engine bay by fuel rail while engine is running as that was where mine was

[Fraz]

Mmmmm was thinking with the heat that it might be expansion in the tank..but half full dont think that would be the case

[Adrian]

I've been looking at the fuel venting systems to try and understand how it works. I've seen the <a href="http://www.v6calibra.com/emissions_control/emissions_control.htm" target="_blank">http://www.v6calibra.com/emissions_control...ons_control.htm</a> section describing the vent valve and carbon canister. I take it that the venting makes it's way from the tank along the third pipe running to the engine bay. But what are all the other pipes around the tank? Looking up to the filler neck there are two pipes going to a squarish box. The Holden manual describes these as an Anti Leak system (presumably something to do with stopping petrol sloshing up out of the filler cap?

Still no sign of any leak now. I hate intermittent faults like this. I like nothing better knowing what a problem is and sorting it out, but you can't fix something that's working properly.

[dj_smurph]

is the car lowered as the steering arms can interfere and wear the hard pipes
the regulator might 'lock out' and stop fuel getting into the return so iy might be there,

check the fuel damper its by the filter these can leak