Raw petrol smell in cabin

[Fast Eddie]

Okay, question for the day.

What is the cause of a strong raw petrol smell in the cabin of my 86 GTV6?

Fairly recently serviced, petrol (98) recently added but tank only half full.

Definitely "new" petrol hence me describing it as raw.  It is not exhaust fumes.

Seems to only happen once after applying a heavy right foot after the car has been doing low speeds i.e in traffic.

I have had it happen in modern cars too. 

Heat?

[Sheldon McIntosh]

Assuming you've checked all the fuel lines in the engine bay, including the little hoses between the rail and the injectors, maybe the vapour canister or one-way valve are blocked?  Does the tank release pressure when you take the cap off?  If so, it'll likely be related to the latter, as it won't be breathing properly.  Maybe... (I'm no expert)

[Al Campbell]

Eddie,

I chased this one for years on my 1983 GTV6 and finally fixed it last summer. Your later car may be different. This got a bit lengthy, so I put a summary at the end. Sorry about my verbosity.

I've had the seal on the top for the fuel level sender leak. I got the smell when it's really hot as the vapour leaks out. Fill the tank to the top and go around a few corners. Then check the top of the tank by removing the interior trim, I could see the wet petrol leaking out on to the top of the tank. That wasn't my only problem. Replaced the rubber seal but still got the vapours.

I then checked that the vapour return line (the plastic one that is routed from the oil separator via the cabin) by pulling the back seats out so you can get at the vapour collection tank (grey plastic moulded) and tubing. I disconnected the hard plastic return pipe from the check valve by removing that rubber tubing (and replace the rubber with new stuff),  then pushed a piece of solid copper wire stripped out of some 240v house wiring all the way through the plastic line till it came out then end near the check valve. Surprisingly easy to do.

Make sure the check valve works while you've got that pipe off. Blow in to the small nipple on the check valve. This valve lets air into the tank when it's cold or under vacuum, not an over pressure release. You should be able to easily blow in. Pull the valve off and try and blow the other way, you shouldn't be able too. With the vapour tank out I cleaned that and checked it for leaks by blocking one end and blowing in the other. There's also a strange double brass tubing restrictor feeding in to the vapour tank that's inside the rubber tubing.

There is rubber tubing that has tight U-bends feeding from the check valve to the vapour tank (replace that),  then a second  bit from the vapour tank under the behind – the –seat cross member into the fuel tank.  But the one under the cross member is a mongrel to get at. I had to drill out some pop rivets to remove the vapour tank. Turns out that and I used a new bit of tubing that was too long and kinked it so much that it blocked completely. It's hard to feed the new tubing under the cross member and get it on to the fuel tank spigot, particularly as the outside diameter of my new tubing was just enough to squeeze under the cross member but then had trouble expanding to slide over the fuel tank input spigot. Not a job for a hot day.

Still with me? When I was pulling the old tubing off the top of the fuel tank I discovered a small metal disk/plug just in the end of the metal tube on the top of the fuel tank. It came flying out when the old rubber tubing finally popped off. It's mentioned in the 75s when chasing odour issues. It's supposed to be some sort of vapour/liquid restrictor and can get blocked with oily gum as the hole through it is quiet fine. I cleaned that and shortened the new rubber tubing. To check that that was all clear I took the filler cap off and blew in to the line into the vapour tank. It takes a bit of pressure but you can blow into the system and hear it flowing.

So:
1.   Replaced the fuel level sender seal.
2.   Cleaned out the hard plastic vapour return line.
3.   Made sure the check valve worked.
4.   Replaced all the rubber tubing behind the back seats.
5.   Cleaned the brass restrictor feeding in to the top of the vapour tank
6.   Checked the vapour collection tank for leaks.
7.   Cleaned the orifice in the restrictor plug at the fuel tank top spigot.
8.   Checked the large fuel cap to tank filler line for cracks and made sure the clamps were firm.
9.   Replaced the small tubing from the from the metal filler tube to the tank – this drains over flow petrol back in to the tank.

That fixed it! With my car, which doesn't have a charcoal canister, the only place excess pressure on in the fuel tank on hot days can go as back through the vapour tank and the hard plastic line to the oil separator on the cam cover. Which would be correct as fumes would then be burnt in the engine. I have heard of some cars having another one way valve stopping vapour from flowing back into the hard plastic vapour line towards the engine, which would leave no where for excess pressure to go with the arrangement in my car.

AL.

[Fast Eddie]

many thanks for the replies both online and via PM!

Some really good info received.

I havent had the time to re-check other than there being no apparent raw fuel leaking into the engine bay as yet so probably a line or the vapour tank.

To hot to check this week (next 3 x days @ 36 deg C) and not expecting to use the car, but will check properly this weekend and report back for interest sake.

[shane wescott]

Just one check I would do, which is where my smell came from:

1. Turn on ignition

2, Remove cover from AFM

3. Turn rotor on afm so the fuel pump starts

4. Listen and smell around under the plenum.

Should find any leaky pipes or leaky injectors.

Catch ya

Shane

[ALFA-GTV2000]

Al, Thanks. (Al Campbell )
I have got the same issue with my '83 2 litre GTV, it has been driving me nuts.
I changed all the Door Seals & Boot Seals, now I will rum thru all your items, especially the Vapor Collect Tank.!!

Deno

[Al Campbell]

Deno,

- Or anyone else, if you replace the short section of tube between the fuel tank and vapour tank. It's a bugger for access as it squeezes between the chassis cross member and the top of the fuel tank. The gap is the same height as the diameter of the tubing. The first new piece I put in was too long and I managed to kink it enough to completely block it.

Remember: "A job's not done properly until it's re-worked".

"Do it again" AL.

[Al Campbell]

Another issue is the way car upholstery absorbs odours. How strong is the smell of Friday night's fish-and-chips on Monday morning? If the rear seats have been soaking up the smell of petrol for maybe a decade, then it may very well keep coming out of the foam on hot days for a while after any leaks have been fixed.

I've toyed with the idea of putting a 12v computer cooling fan on each side behind the rear vent lining under the hatch to force more air out through those venturis (?)

AL.

[ALFA-GTV2000]

Al, I pulled out the Vapour Collection Tank a few Saturdays ago and found the brass(?) valve from the Fuel Tank was totally blocked, cleared out OK. The Fresh Air valve was working fine, hoses seem OK, hold pressure if you blow hard against them.
Probably should replace the hoses anyway.
The smell seemed to improve and my wife was impressed when we went for a quick spin on Sunday.
We went for a long wekend trip for her birthday 2 weeks ago, Coffs to Mnt Tambourine and then down to Mooloolabah.
Car went great, but the smell returned.
(Just as well I got the Air Conditioning working or it could have been divorce time. Air Con issue was another long term project)

It's raining again, so I will probably pull out the parcel shelf and have another look Sunday.

[Al Campbell]

More to check.

Blocked venting arrangements is really obvious after the car is left sitting in the hot sun. Lower petrol level means more vapour to heat and expand so more obvious then than with a low tank. Doesn't show up this time of year in Melbourne hence
took me years to fix the petrol smell in my car.

You have checked under the bonnet like Shane said?

If the smell returns, is it most obvious after you refill? 3 areas if that's the case:

1. The huge diameter tube from the filler cap to the tank often perishes and fuel leaks when you refill, can be hard to diagnose, pull it off and flex it while studying it in strong light.

2. There's also a small overflow or drain tube from the filler cap mount that drains back into the tank.

3. To test the fuel gauge sender seal on the top of the tank, clean the area around the sender by wiping with a rag. Fill the tank to the brim then drive like Fangio for a little bit. Have a look around the sender mount. I could see the petrol getting past the seal and it shows up nice as a wet patch on the metal, clean it off and drive some more. I fixed mine for a short while by tightening the six screws. Eventually had to replace the seal. The original seal on mine looked in good nick, felt pliable and looked like a good design to seal well, but I couldn't stop the leak. Had to replace it with two layers of some fuel proof stuff I got from Clark rubber.

I just have exhaust smells now - wife won't take long trips in it. Door seals are ragged, Hatch seal has shrunk, there's missing and perished seals in my firewall and I even suspect the large rubber plugs in the spare wheel well which are loose and rattle around. Apparently the position of the exhaust tip is critical on these cars.

Good luck, AL.

[GTVeloce]

This was a problem I had in my last GTV and I used to put it down to the unpractical but great looking twin up-swept exhaust tip I had installed. Anyway, thanks to this thread I have gone to the effort (it was exposed anyway) of replacing all the hose in question on my current project and checking the integrity of the fresh air valve which was fine. I then discovered my brass valve was also blocked but managed to unblock it via solvent and a piece of wire.

Now I am in the search for replacement rubber hosing between the filler pipe and the tank. Not so easy. Does anyone know a suitable supplier in Melbourne? Or could I try the silicone hoses more commonly used in engine bays of turbo charged vehicles? Will it handle fuel without perishing?

Finally, on the 2L GTV's the overflow pipe doesn't go back into the tank but drains (via hose) straight down and out. I suspect the 6's go to the tank.

Thanks
Julian

[Al Campbell]

I don't think silicon is petrol proof,  maybe exhaust proof, but not liquid petrol. Pretty sure, but could well be wrong. IMHO, getting old & forgetful &c...

I seem to remember the GTV6 spill drain does go back into the tank, Just take a quick look, it's not hidden. I think the 75 drain through the floor, but the tube can get dislodged and then drain into boot - but I've never been in the boot of a 75...

Easy way to test fuel proofedness. Cut off a piece of your stuff, measure it (i.e. 10mm square) and put it in a glass jam jar full of petrol with the lid on. Leave it for a few days then measure it. Or notice over night that the little piece is now twice the size. I went through this making a new seal for the fuel sender. Clark Rubber's website disagreed with the labels in the shop on which material was fuel proof or not. Went to buy some, another shop assistant overheard the conversation said : "No. No. you've got it wrong, this other stuff is definitely fuel proof." It wasn't of course.

AL.