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Don't fill your vehicle with fuel


WhiteTruckMan
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Might be a bit late, but with the hot weather we are having, I thought I would tell people not to fill their cars to the brim with fuel. This warning is prompted by last nights site of a night trunker coming in to work, checking the fuel cap on his tractor and getting showered in diesel. The last time he finished, he filled up for the next driver (as is normal), parked up and went home. By an odd set of circumstances, his vehicle wasnt used yesterday, so his fuel tank was in the hot sun all day, heating up and pressurising the tank as the fuel expands. And 600 litres produces a lot of expansion. such that when he checked his cap it came showering out. On him.

The obvious lesson here is that if you do this with your car, then although you probably wont get showered, cars have plastic tanks and fillers, so the chances of a rupture are that much greater. And in this heat thats a lot of dangerous fumes for the unwary. (diesel is safer as I think its flashpoint, the temperature at which it starts to give off flammable vapours, is around 60 degrees, from memory). Plus fuel is too expensive to waste.

So if you simply have to top it off, please do it just at the start of a long journey.

WTM

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Forum Editor

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All car fuel tanks have pressure relief valves built in. It's theoretically impossible for fuel from a car's petrol filler cap to burst out when the cap is removed in hot weather.

I've opened the filler cap on a car that had been standing with a full tank for several hours in the sun in Nevada, and nothing untoward happened. The temperature was somewhat North of 100 degrees F.

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WhiteTruckMan

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I was curious enough to do a little digging and it turns out that the coefficient of diesel is about 0.00083/°C From

More than you EVER want to know about diesel

(apparently its even higher for petrol)

So a car with a largish tank, say 75 litres, filled in the morning on the way to work - assuming work is close by the fuel station - and left in a hot sunlight all day can reasonably raise the temperature by 15°C in the tank. This comes out to the best part of a litre in volume, and if the tank has been brimmed, then I wonder how much pressure is going to result. But I do know that although diesel has many interesting properties, compressibility isn't one of them!

WTM

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morddwyd

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"one of the legal sign off tests for a fuel tank is to start a fire underneath the tank."

I believe they're going to make that part of the MoT.

"If this didnt happen then a vacuum would be created in the tank resulting in the engine running unevenly and eventually stopping"

In the 50s/60s one of the first things to check on a motor bike if the engine suddenly petered out was the vent in the fuel cap (gravity feed, so it didn't take much). Used to be the first thing an AA?RAC patrolman would check.

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WhiteTruckMan

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**"one of the legal sign off tests for a fuel tank is to start a fire underneath the tank. I believe they're going to make that part of the MoT.**

Given that most car fueltanks are plastic these days, do let me know how that works out, while I stand back. A long way back.

Incidentally, things seem to have wandered away from my main point, which is that fuel expands in hot weather, so dont overfill your tanks.

WTM

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spuds

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Perhaps going off subject, but I find that fuel and mileage comparisons very confusing, as to what manufacturer's state and what the vehicle owners anticipate. And if evaporation might be a questionable answer?.

Eddie Stobart are perhaps one of the main haulage company's who have strict monitoring of their vehicles, and perhaps especially more so with 'dual-fuel' vehicles in their fleet.

On the public side of things, I once had a brand new Hillman Avenger estate, and I could never get the fuel- mileage results the manufacturer and retailer were stating. my checks were based on a simple 'top-up' and speedo comparison check. The retailer and manufacturer did a far simpler comparison check, by installing a one gallon fuel tank direct to the carb, then conducting a series of different terrain and speed checks. Their one gallon check proved more conclusive, than the checks I had undertaken over a period of time, so it was a case of accepting their figures. But I still wasn't very happy about the 'lost' consumption of petrol?.

Another incident that I had was with a new Vauxhall 2000 I had many years ago, and the fuel results from that. Eventually one of the problems found, was a hairline slit in the fuel pipe, which due to evaporation and location was hard to find. It was only due to poor fuel consumption that this was identified?.

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WhiteTruckMan

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Back in the day I had an 88" series 3 landrover 2.25 petrol that wouldnt achieve manufacturers stated fuel consumption figures even if you towed it with a team of horses while the engine was switched off!

WTM

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Quickbeam

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I don't believe for a minute that you couldn't get at least 10mpg with careful driving out of your 2 and a quarter petrol landrover WTM.

I used used to achieve that quite easily out of my series 2 whilst going down a 1in4 bank. Maybe your carburettor needed a service...

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spuds

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Does a series one, which on occasions of speed, had flames coming from the exhaust count as a fuel guzzler?.

Sold that for £49.00 and have regretted ever since :O(

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wiz-king

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WTM - you shouldn't have used the petrol cab heater grin

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spider9

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WTM

Your calculation of the deisel expanding by 1 litre with a 15 degree rise in temp will be somewhat offset by the metal tank also expanding with the same temp rise, surely?

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