Fuel tank vents
Discussion
Life is never simple. I'm working my way around my new acquisition and trying to get rid of the smell of petrol in the garage. Like every car I've had with 'Aero' style filler caps a quick tweak to make sure the O-ring seal is firmly seated when the caps are locked in position made a significant difference. I then noticed the tank breather tubes are just open to atmosphere which also explains the vapour problem. My problem is the tube used on the car for the vent is 6mm bore and an inline breather valve with push on fittings is only available in 8mm so I've had buy fittings to take the 6mm to 8mm to the valve and then 8mm down under the car to atmosphere. Is this what everyone else has done? The vent I'm using is a Newton TPV8.
BobE said:
Life is never simple. I'm working my way around my new acquisition and trying to get rid of the smell of petrol in the garage. Like every car I've had with 'Aero' style filler caps a quick tweak to make sure the O-ring seal is firmly seated when the caps are locked in position made a significant difference. I then noticed the tank breather tubes are just open to atmosphere which also explains the vapour problem. My problem is the tube used on the car for the vent is 6mm bore and an inline breather valve with push on fittings is only available in 8mm so I've had buy fittings to take the 6mm to 8mm to the valve and then 8mm down under the car to atmosphere. Is this what everyone else has done? The vent I'm using is a Newton TPV8.
Doesn't matter what valve you have, you will always smell petrol unless you fit one of these; a carbon vapour canister, there are many here.... http://www.ebay.co.uk/sch/i.html?_from=R40&_tr...
Pick one and see.
I appreciate that response but it's not so simple to fit one of those as they also have a purge function into the engine induction system. The type of valves I'm fitting will only release vapour if the tank becomes slightly pressurised and then will close off again limiting the amount of vapour released.(They will also allow air into the tank as fuel is used when a slight vacuum is drawn). I guess what is really needed is something like a small crankcase vent filter on the end of the tube from the vent valve filled with activated carbon but I'm not aware of anyone making such a product. If anyone knows different please let me know!
BobE said:
I appreciate that response but it's not so simple to fit one of those as they also have a purge function into the engine induction system. The type of valves I'm fitting will only release vapour if the tank becomes slightly pressurised and then will close off again limiting the amount of vapour released.(They will also allow air into the tank as fuel is used when a slight vacuum is drawn). I guess what is really needed is something like a small crankcase vent filter on the end of the tube from the vent valve filled with activated carbon but I'm not aware of anyone making such a product. If anyone knows different please let me know!
So use a small version of the above and block off the purge pipe leaving only the vent.because the stock tanks available dont fit n the space available I designed a tank that fits in the corner of the bulkhead just inboard of the cage arms in the little pocket. tank has a splitter in the middle of the tank that goes up 80% of the way. bought a tank cut it in half and recovered the charcoal filled my new tank on both sides. Fumes come in from bottom up through the media over the top of the splitter and down through the second chamber out the bottom. simple but it has worked well the only time I ever smell fuel is right after a fillup but the smell goes away quickly and does not return until the next fillup and then only if I top the tanks which I only do on long trips. Lee 
Edited by ROWDYRENAULT on Tuesday 28th February 17:51
My solution was simply to run some rubber hose from the connectors on the tank tied to a chassis rail down to the bottom of the engine bay and leave them open to vent. Fuel smells gone.
Parts needed are about 4 feet of rubber hose (for 2 tanks) 2 jubilee clips and some cable ties.
Mark
Parts needed are about 4 feet of rubber hose (for 2 tanks) 2 jubilee clips and some cable ties.
Mark
mt308 said:
My solution was simply to run some rubber hose from the connectors on the tank tied to a chassis rail down to the bottom of the engine bay and leave them open to vent. Fuel smells gone.
Parts needed are about 4 feet of rubber hose (for 2 tanks) 2 jubilee clips and some cable ties.
Mark
That's what the car currently has and the fumes from the tanks vent into the garage.Parts needed are about 4 feet of rubber hose (for 2 tanks) 2 jubilee clips and some cable ties.
Mark
Life may still not be simple.
Many years ago I also had fuel smells that I wanted to eliminate. I was fortunate to be working at a large aerospace/defence company and had access to some very sophisticated tools and equipment.
I borrowed a gas tester and worked my way around the engine bay.
By far the highest reading was sniffing alongside braided hoses. Had very low reading from the tank breather and only slightly higher in the throat of the carb.
Steve
Many years ago I also had fuel smells that I wanted to eliminate. I was fortunate to be working at a large aerospace/defence company and had access to some very sophisticated tools and equipment.
I borrowed a gas tester and worked my way around the engine bay.
By far the highest reading was sniffing alongside braided hoses. Had very low reading from the tank breather and only slightly higher in the throat of the carb.
Steve
Steve_D said:
Life may still not be simple.
Many years ago I also had fuel smells that I wanted to eliminate. I was fortunate to be working at a large aerospace/defence company and had access to some very sophisticated tools and equipment.
I borrowed a gas tester and worked my way around the engine bay.
By far the highest reading was sniffing alongside braided hoses. Had very low reading from the tank breather and only slightly higher in the throat of the carb.
Steve
Not all braided hoses are fuel compatible, now especially with the use of ethanol.Many years ago I also had fuel smells that I wanted to eliminate. I was fortunate to be working at a large aerospace/defence company and had access to some very sophisticated tools and equipment.
I borrowed a gas tester and worked my way around the engine bay.
By far the highest reading was sniffing alongside braided hoses. Had very low reading from the tank breather and only slightly higher in the throat of the carb.
Steve
mt308 said:
My solution was simply to run some rubber hose from the connectors on the tank tied to a chassis rail down to the bottom of the engine bay and leave them open to vent. Fuel smells gone.
Parts needed are about 4 feet of rubber hose (for 2 tanks) 2 jubilee clips and some cable ties.
Mark
That's what I have and have never had fuel smells in the garage.Parts needed are about 4 feet of rubber hose (for 2 tanks) 2 jubilee clips and some cable ties.
Mark
A couple of points. Firstly I agree not all braided fuel hoses are the same. I once had a Marcos LM500 and the main feed from the tank was a braided hose that was actually damp to the touch with petrol. A better grade replacement solved the issue. Secondly petrol vapour is heavier than air so it will tend to be present at floor level with the vent pipes going down to the lower chassis rail with no valves fitted. I'm afraid my garage does not yet have sealed doors so with all the wind we've had lately the fumes have been blown up around the internal volume of the room.
barpilot said:
Which valves did you fit to cure the issue? I'm wanting to fit something to prevent any similar problems.
To cure the issue I did several things. Firstly you want to make sure the filler caps locate correctly and ensure the O - rings seal fully in the filler neck. When you take the cap off there is a small hexagonal nut on the rear that you can tighten slightly making sure when the cap is replaced you can still easily pull and push the 'lever' to lock/unlock the cap in the filler neck. I also checked the tightness of all the socket head screws that hold the filler cap assembly to the body to make sure there was no leak path there. (You need very flexible hands to get a spanner/ socket to some of the nuts).Then on my car there was a 6mm brass connector from a vent in the rubber cone part of the filler assembly to which was fitted a 6mm bore hose down to the lower chassis rail. The valves I used are these:https://www.merlinmotorsport.co.uk/p/newton-inline...
You can only get them for use with 8mm bore tube so I had to have a short length of the original tube from the rubber cone to a 6mm/8mm fitting such as this:
https://www.merlinmotorsport.co.uk/p/steel-hose-jo...
The valves are fitted with the grooved part towards the tank.
Then a short length of 8mm tube to the vent valve and then more 8mm tube down to the chassis rail. The tubing I used from a local supplier was to SAE J30 R6 which is OK for unleaded fuel with modest ethanol content - and will also take under bonnet temperatures.
The valve works by normally being closed but as fuel is drawn from the tank it will open to atmosphere to stop a vacuum being drawn. If the tank gases expand and start to pressurise the tank - if it gets hot when the engine is turned off and heat soaks for example - it will allow the excess pressure to vent. You may very occasionally get some fumes being released because of the latter but they are very minor and isolated releases.
That's what I did on my car and it has made a huge difference. If a car was built using the wrong grade of fuel hoses then the ethanol content in the latest petrol grades could start to break down the rubber material and you'll get fumes from there.
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