Fuel Tank Fuel Filler leakage

[bob_rich]

Hi Folks

Been running the +2 to run it in a bit and get the feel of it after the rebuild. I have noticed that after filling up the tank to around 3/4 full and when the fuel level in the tank is around 4 to 5 inches below the top of the filler pipe that after a reasonable run of around 10 miles there is evidence of fuel streaking along the rear wing down from the fuel filler cap. The tank is a standard one with the filler tube about half way up the left hand side and the tank is raised up around 1.5 inches to get the fuel pipes through to the front.

The car is modified to use fuel injection so the layout is quite different to standard. I have attached a drawing of how it is arranged. The cap a new locking one is a reasonable fit but I assume it has to vent a bit as with the fuel injection mods the fuel vent pipes are not now installed.

wondering if anyone else has had this problem and how they might have delt with it

thanks in advance for any info

bob

[mbell]

As John said in the other thread most likely a badly sealing filler cap or filler cap with vent hole. All other leaks would be under the car or in the boot.

I don't think it is related but where does tank actually vent to atmosphere? From your diagram it appears that it is a closed system (when the filler is sealed) with no external air vents. So there has to be a leak somewhere to allow air in to replace the fuel as it is used by the engine or to let air(pressure) release if the fuel temp increases and it expands.

[bob_rich]

Hi

I had assumed, and did check, that the fuel filler was not a "really good" seal. so that small rate of change of volume with consumption of fuel would permit some venting via the cap. In a normal +2 with the pipes in the roof space there is adequate ventilation so the cap would not matter ( perhaps even too much !)

My problem suggests that there is enough ventilation through the filler cap it is the sucking out a small amount of fuel when fairly full that appears to be the issue- - or maybe it slops out on braking or cornering either way a solution would be nice.

bob

[elansprint71]

Bob,
I suggest that the answer to your problem might be outwith the compass of knowledge of members of this forum; probably only a handful of folks have done what you have in fitting fuel-injection to the +2, however thousands will have done this with other Ford-based applications. I suggest that you check out the Cortina and Escort forums.

I think one of the problems might be that the fuel tank in the +2 is fitted very high in the system; from memory of a conversation with Ron Hickman, there was a heated debate over "packaging" in the "just too small" dimensions of the car- in an ideal engineering solution the fuel tank(s) would have been under the rear "seats" but other vital stuff was in the way.
The aspiration was to create a comfortable "family express" which would not need to be topped-up every 200 miles; the "low-down-tank engineering solution" was never going to work in the given envelope, so the tank finished up over the axle and out of the luggage space. Just imagine if the design brief for the +2 had been for a two-seater Gentlemans' Express- a GE, rather than a GT.

[mbell]

I had assumed, and did check, that the fuel filler was not a "really good" seal.

My guess is that is your problem. The filler neck is only slightly above the top of the fuel tank on the +2. So it wouldn't take much lateral load (right hand corner) or camber for the filler neck to be below the fuel level and fuel make it's escape.

I'd do a temp job to try provide a better seal on the filler neck and see if the problem is fixed/reduced to confirm it is the issue.

Longer term I recommend sealing the filler cap and adding the small bore breather as per +2 breather mod (attached), then connect the swirl pot and breather somewhere near the middle/top of the tank on the larger bore pipe.

[DavidLB]

i had exactly that problem on my S130, also with fuel injection. solved using anMX5 part.they used a non return valve in the fuel filler pipe. bought a used pipe from the web, its a slightly smaller dia than the elan one so you will need a a reducer Car Solutions have them. problem completly solved. pm if you need further info

[Robbie693]

Hi Bob,

This is a common problem and the reason is that a Plus 2 should not have a vented cap. Because the filler neck enters the tank halfway down it's side the neck fills with fuel, this then gets sloshed out on right hand bends through the vented cap.

The only way to stop it (without buying non-return valves) is to seal up the vent hole or buy a non-vented cap. This means you will need a vent elsewhere in the system of course and was the reason the Plus 2 had those ridiculous pipes going over the roof...

Cheers

Robbie

[EPA]

Hi Bob

The link below will take you to my post regarding the MX5 insert

Ed

lotus-carbs-f40/fuel-spillage-from-filler-t31759.html

[bob_rich]

Hi All

Thanks for all the useful tips. It is nice to get an understanding of the problem, and conformation that it is real. and the solutions all seem interesting. I will look at the cap sealing but before I seal it will look at how to best fix a suitable vent.

Thanks for all the advise and ideas

cheers

Bob

[bob_rich]

Hi Folks

Following the suggestions I can confirm that the fuel cap did have a bleed hole in the cap so I modified the breather system to add a second in roof vent tube that T'd off from the drivers side vent pipe. I then took this pipe through the roof space and terminated it in the original hole where the LH pipe terminated. I also soldered up the vent hole in the fuel cap. I filled up the car with fuel to around 5" below the filler and on the 6 mile or so drive back from the filling station there was no sign of fuel leakage. In the past even if I could not see the fuel in the filler pipe ther was some leakage form the filler cap. Hopefully this will have sorted the problem

I have attached a modified drawing showing how the system now looks with the changes to the original sketch shown in red

thanks for all the help

Bob

[bob_rich]

Hi Folks

Following the suggestions I can confirm that the fuel cap did have a bleed hole in the cap so I modified the breather system to add a second in roof vent tube that T'd off from the drivers side vent pipe. I then took this pipe through the roof space and terminated it in the original hole where the LH pipe terminated. I also soldered up the vent hole in the fuel cap. I filled up the car with fuel to around 5" below the filler and on the 6 mile or so drive back from the filling station there was no sign of fuel leakage. In the past even if I could not see the fuel in the filler pipe ther was some leakage form the filler cap. Hopefully this will have sorted the problem

I have attached a modified drawing showing how the system now looks with the changes to the original sketch shown in red

thanks for all the help

Bob