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GT40 Tech - Fueling, Electrics, & Engine Cooling Petrol, Electrons, & Water

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Old 30th April 2018, 07:13 AM   #1
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john_douglass
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Strange Gas leak - KVA

I had a strange gas leak several days ago. I decided to take my baby (a KVA GT40) out for a spin as she had been sitting in the garage all winter. As I backed out of the garage I noticed a stream of fluid coming from under the car Ė later I recognized that it was gasoline. I followed my usual routine of giving her a shot of laughing gas (starting fluid) to help her start after sitting a long time and she started right up.

After putting her back in the garage I did a thorough test of the gas plumbing. She has dual side tanks, dual off/on switches, dual fuel lines and filters, etc. However, I canít find any leaks. Iíve run each fuel pump several times, started the engine but canít find any leaks.

Is it possible that the side tanks have some kind of pressure release valve that vented the gas? Is this a problem I should worry about?

John

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Old 30th April 2018, 08:54 AM   #2
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Re: Strange Gas leak - KVA

Any fuel leak is something to worry about. Assuming you've checked all the hoses and connections, the leak may be the tank itself. Was the leak on one side or the other or under the engine? I don't know what type of tank the KVA has and you don't mention the general location of the leak but if the fuel is in a bladder in the sponson it may have delaminated. If is is in an aluminum or steel tank, a seam weld may have failed. The tank probably has access ports for foam (or other anti-slosh) as well as the fuel level sending unit and one of those gaskets may have developed a leak. If the tanks were full then the latter may more likely be the issue. If it is very slight seepage, that may be the reason the issue wasn't noticed until your run after prolonged winter storage as the fuel accumulated over time. In any regard, I would definitely pull things apart until you found the source.
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Old 30th April 2018, 10:24 AM   #3
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Re: Strange Gas leak - KVA

I agree with veek. Any leak fuel leak is bad. Chase it till you find it. There are many reasons for a fuel leak. A bad check valve could cause you to pump fuel from on tank to the other, causing it to over flow. Sounds like you have a slow leak. Fuel bladders are known to leak after time, but fuel lines and hoses and fail also. Where exactly is the fuel under the car?
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Old 30th April 2018, 12:19 PM   #4
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Re: Strange Gas leak - KVA

Guys,

If the bladder or aluminum side tank had a leak, wouldn't I see some leakage under the side tank? I've checked these thoroughly and there no leak under the side tanks - I've been monitoring them daily for leaks.

John
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Old 30th April 2018, 01:43 PM   #5
Walt Williams
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Re: Strange Gas leak - KVA

Yes... Keep watching for the leak.. Can you smell gas in the garage? Are you sure it was gas? You can not repair it till you find the leak.. I would check all clamps and hoses. Se if any are loose. Check the filler hoses and clamps.
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Old 30th April 2018, 02:21 PM   #6
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Re: Strange Gas leak - KVA

Ok I have seen this on a KVA but remember each car is an individually built car so it may or may not be the same as yours.

Tank to facit fuel pump to filter and pressure regulator to T piece to carb, and the same for the other side!

Now early Facits had a non return valve built in bit these were known to fail.

So turn on left tank and pump rattles away and fills carb, and then pressures to 4.5 psi and the non return on the other tankís pump fails and the fuel returns to the opposite tank and over fills it and once in this state the fuel will exit through the overflow valve/roll over valve or what have you.

Turn off the car and the non return valve has now had the crud washed out, seals better and when you look no more leaks. BUT it will leak again.

Fit some purpose made non return valves in the fuel lines in conjunction to the pumps and filters and problem solved.

Well it was in the car I saw this on!

Ian
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Old 30th April 2018, 03:09 PM   #7
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Re: Strange Gas leak - KVA

Remember that todays ethanol laden fuels raise havoc with anything rubber!
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Old 30th April 2018, 07:25 PM   #8
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Re: Strange Gas leak - KVA

John,
One other thought, check and see if your carb float is sticking and that float needle and seat are smooth and without debris. Your float should also not have any fuel inside. Needless to say a hot engine wet with fuel is a recipe for an unpleasant KVA flambe.
To Bud's point, ethanol can ruin the carb internals creating all sorts of problems.
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Old 30th April 2018, 10:02 PM   #9
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Re: Strange Gas leak - KVA

Ian,

My setup has a fuel filter after the gas tank-> to fuel pump->red inline device with a one way arrow on it -> tee splitting the line -> carb. I assume that this red inline devices is the "non return" device or valve that you're referring to.

What you're suggesting is that this "non return" device or valve may be failing allowing gas to pump from one tank to the other. You're saying fuel returns to the opposite tank and over fills it and once in this state the fuel will exit through the overflow valve/roll over valve.

Then if this is the case, I might need to replace both "non return" valves.

I have the scent of gas in my garage which I am unable to eliminate!

John
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Old 1st May 2018, 01:20 AM   #10
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Re: Strange Gas leak - KVA

Hi John

If you have non return valves fitted already it would be cheap insurance to replace them as they are only a few pounds each.

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Old 1st May 2018, 07:54 AM   #11
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Re: Strange Gas leak - KVA

You didn't mention what carb, but on start-up after winter I have twice had leakage from the transfer tubes on a Holley, and replaced o-rings.
When I turned the tubes between my fingers (as they just sit in the o-rings with no mechanical fixing), the leak has stopped, but for safeties sake I have replaced the O-rings anyway. I am inferring from this that the leak could have stopped with vibration after you started up.
Also, old hoses can start to leak after a spell of cold weather.
I now always check the system after winter, pressurising the system and pulling at each connection to check for leaks before I dare start the engine - nothing scarier than starting an engine while fuel is being sprayed about!
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Old 1st May 2018, 08:07 AM   #12
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Re: Strange Gas leak - KVA

It would be helpful to know:
How full are your tanks? If the gauge is significantly less than full on both sides, it is less likely the pumps are overfilling from one tank to the other (assuming your gauges are accurate).
Where on the garage floor was the fuel (front, back, or side of the car)?
Was it wet around the carb?
Do you have a picture of your fuel pump, the "red inline device" and the filter?
Have you pulled the cladding (fiberglass that curves around the sponson)off the car to look for leaks.
What kind of tank do you have and can you access it (or the gauge sending unit)?
If you can, is there a strong fuel odor?
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Old 1st May 2018, 10:54 AM   #13
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Re: Strange Gas leak - KVA

Quote:
Originally Posted by 40bud View Post
Remember that todays ethanol laden fuels raise havoc with anything rubber!
Gates advises to replace all rubber fuel hoses within every 3 years. In my experiance not even two years.
Old stock fuel hose ( most automotive stores sell old stock as low pressure carb fuel hose is uncommon these days) I have seen them gone within 6 months.

Fuel hose SAEJ30R9 or higher is ethanol proof. J30R7 and lower is rubbish.
Fuel hose without SAE numbers, don't even think about it.

I am a dealer of Cohline 2134 in Holland which has E10 (10% ethanol) rating.
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Old 3rd May 2018, 07:05 AM   #14
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Re: Strange Gas leak - KVA

Guys,

I think I've solved the riddle of the strange gas leak - actually the answer was provided within 24 hours be Steven who goes by the moniker of Stevenx40. He suggested that the "carb bowl floats sticking after sitting over winter" may have caused the carb to overflow.

A critical clue was the persistence of a gas odor in my garage. No matter how I vented the garage the smell persisted. I knew then that there was an open source of gas in my garage. It turns out the gas had pooled under my intake manifold - it's a tarantula intake manifold and has a cavity that's partially hidden under the carb. Iím running a Holley 570 Street Avenger carburetor which is a dual pumper. I checked the intake manifold carefully and there was still evidence of gasoline. I knew then that carb float must have been sticking which allowed the carb to overflow.

I cleaned up everything and will start the engine again - I decided not to take the carb apart right now figuring that the float would become unstuck.

It will be about a week or so before I get a chance to check everything out - thanks for all your suggestions and Iíll keep you posted!

John
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Old 3rd May 2018, 10:53 AM   #15
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Re: Strange Gas leak - KVA

Quote:
Originally Posted by JP Verweij View Post
Gates advises to replace all rubber fuel hoses within every 3 years. In my experiance not even two years.
Old stock fuel hose ( most automotive stores sell old stock as low pressure carb fuel hose is uncommon these days) I have seen them gone within 6 months.

Fuel hose SAEJ30R9 or higher is ethanol proof. J30R7 and lower is rubbish.
Fuel hose without SAE numbers, don't even think about it.

I am a dealer of Cohline 2134 in Holland which has E10 (10% ethanol) rating.
As a note to those who have spent a LOT of money on buying stainless jacketed braided hose such as that available from Russell, Aeroquip, et al - you are NOT necessarily in the safe zone. Only recently (2-3 years) has the hose sold by most suppliers been replaced with Teflon lined hose or hose with rubber / neoprene formulated to withstand use in a system using alcohols like ethanol and methanol..
Yes it all looks good on the surface, but the real problem is in the hardening of the lines, followed by cracking and sluffing off of the rubber within the lines.
The rubber bits shed will then be trapped by your fuel filter or carburetor etc...
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Old 6th May 2018, 12:31 AM   #16
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Re: Strange Gas leak - KVA

Any fuel on the intake man? How did the engine run? A stuck needle and seat may have fixed itself.
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Old 6th June 2018, 11:55 PM   #17
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Re: Strange Gas leak - KVA

Guys,

After a long delay in getting to work on the car (seem like we have a monsoon season here on the East Coast of the USA), I found out that a braided gas like to the carb was bad. Replaced it and I'm good to go.

I'm going to take the advice of some of you and replace all my rubber gas lines.

Thanks for all your suggestions!

John
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