in five years of having my car on the road i've come across this problem for the 1st time and i don't like it at all!

took my indy to work today, had it parked in the workshop nice and safe but then this afternoon was sure i could smell petrol, no one else could but i was sure of it! time to come home, jumped in and it refused to start, was obviously flooded but had no idea why, 1 flat battery and a jump start later it went but wasn't running very well, got it home and when i parked up on the drive and switched off i could hear fuel going into the carb! took the air filter off and the carbs were just about to overflow with fuel!

only reason i could think of was pressure in the tank, took the cap off and big woosh! now i'm guessing the cause of the pressure is the combination of me using the car a lot lately and thus the fuel tank is almost empty and the unusually hot summer.

so there is the story behind what's happened now what i need to do is figure out how to put it right to stop it happening again.

can i get a different cap that will allow the pressure to escape? or is there a specific valve i need to get and fit to the tank?

any help much appreciated as A. i find this quite worrying and B. the sump is full of petrol now so i can't even move the car until i've been for some oil!

this is what you want in the top of your tank

http://www.merlinmotorsport.co.uk/p3556/ROLL-OVER-VALVE-1/4-X--6JIC/product_info.html

a one way valve will be needed that closes if the car rolls over obviously needs to be higher than the fuel filler

The simplest way is to drill a small hole somewhere around the filler cap.

A small hole stops the tank pressurising, does not seep to much, even if the car does turn over, and does not cause any evaporation problems.

you can get one from Car Builder solutions for about £8, which has 2 x 8mm tails so can just put in line in a hose from the tank. The small (2mm) hole in the filler cap works well also.

quote:

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Originally posted by Antnicuk
you can get one from Car Builder solutions for about £8, which has 2 x 8mm tails so can just put in line in a hose from the tank. The small (2mm) hole in the filler cap works well also.

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If you don't want to drill a hole in the tank you can mount a small fitting in the filler hose just above the tank and vent it to the outside.
This is the way US cars were built until environmental situations changed.
If you are nervous about rollover put a valve in, but this will not help in your present situation were pressure and not vacuum is building in the tank.

I have 1 of these and no problems.

poo

quote:

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Originally posted by dave
I have 1 of these and no problems.

poo

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http://www.demon-tweeks.co.uk/Motorsport/Fuel_System/Fuel_Tank_Vent_Valves/Mocal_Fuel_Tank_Pressure_Relief_Valve/1546/0/23336

they do a cheaper one that fits to a weld in boss as well

either will do what you need and vent under pressure or vacuum

quote:

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Originally posted by dlatch
http://www.demon-tweeks.co.uk/Motorsport/Fuel_System/Fuel_Tank_Vent_Valves/Mocal_Fuel_Tank_Pressure_Relief_Valve/1546/0/23336

they do a cheaper one that fits to a weld in boss as well

either will do what you need and vent under pressure or vacuum

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quote:

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Originally posted by 40inches

quote:

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Originally posted by dave
I have 1 of these and no problems.

poo

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This is also a one way valve, air in, but not out for the OP's problem he needs a 2 way valve, I haven't found one for under £30

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I got mine from ThinkAuto - not too expensive, IIRC.

LINKY

now that's slightly more locost! merlin want a tenner to deliver theirs!

i'm looking at the trv45 from think, does that look right?

It's worth ringing the people at Think - you can have an intelligent conversation with them, as they generally seem to know what they're talking about.

On-phone prices for P&P tend to be lower too - these valves weigh next to nothing, so you end up paying for whatever it costs (e.g. a padded envelope and stamps) rather than an arbitrary standard charge.

[Edited on 10/7/10 by David Jenkins]