petrol smell when vents open

[daisyman]

evening all.This might seem a daft question but why does my bus stink of petrol when the hot air vents are open but when closed the smell stops? I thought that only fresh air was drawn in through the blower and across the heat exchangers.By the way its a '71/72 crossover.

 

[Araon]

a few pics of the engine bay may answer that one

any number of reasons from perished fuel pipes, perished/missing seal around the front of the engine bay, unburnt fuel entering worse for wear exchangers...

any exhaust fumes aswell or is it just strong fuel?

 

[ProfessorWheeto]

Don't forget the breather pipe on top of the fuel tank, that sometimes gives off a fuelly smell in the cabin.

 

[Trikky2]

If your getting a petrol smell I strongly recommend you check the fuel pipes and replace them if they are dodgy. Don't forget the one from the tank itself while your at it. All connections should have good quality hose clips.

If the fuel lines are all good then check the pump and carb. If you have fuel leaking or seeping it will leave a stain so its easy enough to spot.

There should definitely not be any smell of fuel or exhaust with the heater running. If there is theres something wrong so fix it before it might lead to something serious.

 

[daisyman]

Thanks for the advice. Looks like engine out time. Still as its snowing now,can't see me using her in the immediate future.Happy Christmas all.

 

[Trikky2]

Looks like engine out time.

??? to check the fuel lines???

 

[froggy]

Looks like engine out time.

??? to check the fuel lines???

To check the breather pipes on top of the tank.
If your going to this much trouble you might aswell change the pipes to be on the safe side, also change the filler pipe (think its 55mm)

 

[daisyman]

Sorry,didn't mean to sound stoopid when I said engine out.Obviously I am goin to replace all pipework that cant be done with engine in....might be able to check/sort out the progressive carb as well seeing that I will be able to access the mixture screw more easily as well as check the choke operation (can I run the engine on a large piece of wood balanced on a trolley jack?).Probably all going to end in tears but you never know unless you try.

 

[froggy]

You can get to the mixture screw with the carb in place, just use 1 of the small screwdriver bits that come with the cheapo screwdrivers. The mixture screw shouldn't be overly tight (i adjust mine just using my fingers!)

To change the fuel tank breather pipes it is an engine out job unless you dont have a fire wall fitted (cant remember but think on some certain years they weren't fitted)

 

[daisyman]

with regards to the smell,a friend had a look and spotted that there is a breather pipe (rubber) coming from the oil filler next to the breather pipe(metal) that is connected into the bottom of the air filter(aftermarket pancake style ontop of a weber progressive carb).He says that the pipe shouldn't be connected as it will clog up the filter and make the engine run rich which could also be contributing to the smell.(I am thinking that maybe the heat exs are leaking which could be why the smell only comes when the heating vents are open).Now thinking about changing heat ex and disconnecting rubber pipe,cleaning filter before tackling petrol filler pipe and breather.Any comments?

 

[Frankie]

If you say what area you are in then there might be someone on here who could pop round and have a look best to be safe .

 

[froggy]

with regards to the smell,a friend had a look and spotted that there is a breather pipe (rubber) coming from the oil filler next to the breather pipe(metal) that is connected into the bottom of the air filter(aftermarket pancake style ontop of a weber progressive carb).He says that the pipe shouldn't be connected as it will clog up the filter and make the engine run rich which could also be contributing to the smell.(I am thinking that maybe the heat exs are leaking which could be why the smell only comes when the heating vents are open).Now thinking about changing heat ex and disconnecting rubber pipe,cleaning filter before tackling petrol filler pipe and breather.Any comments?

The air pipe from the oil filler to the air filter is part of the crankcase breathing system and SHOULD be connected, it doesn't clog up the filter as it fits inside the filter and supplies the carb with a warm air feed. On a standard set up this pipe feeds back into the oil air filter and does the same thing.
One thing i can recommend though is checking the petrol cap as i had issues with mine doing the same thing as yours (fuel smells when the vents were open) i ended up changing all the fuel lines, all the breathers and a new petrol cap - no more fuel smells but not sure what cured it :?

 

[Trikky2]

with regards to the smell,a friend had a look and spotted that there is a breather pipe (rubber) coming from the oil filler next to the breather pipe(metal) that is connected into the bottom of the air filter(aftermarket pancake style ontop of a weber progressive carb).He says that the pipe shouldn't be connected as it will clog up the filter and make the engine run rich which could also be contributing to the smell.(I am thinking that maybe the heat exs are leaking which could be why the smell only comes when the heating vents are open).Now thinking about changing heat ex and disconnecting rubber pipe,cleaning filter before tackling petrol filler pipe and breather.Any comments?

Sounds to me like you need to decide exactly what it is you are smelling first.

Is it petrol or exhaust fumes or crankcase fumes. Its not difficult to tell these apart.

 

[daisyman]

thanks for all replies.have found out that I have a late type fuel vent system that exits to the petrol cap area.As for the smell,I am sure it is petrol but could be petrol enriched exhaust.Any body live in the banstead (surrey) area as help/advice would be greatly appreciated.