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MG MGA - Is an empty gas tank really empty ?

Last night I barely made it home. My MGA was sputtering,spatterring and choking itself to death. Althought the gas guage said I had app. 1/8 - zero of a tank of gas left ...the guage has not been very reliable.

Cracking open the gas line, at the front float bowl, I did a flow test and not surprisingly the flow of gas was terrible to none. It spatterred and spitted very little gas. Working on the assumption that the tank was empty I thought it would be a good idea to remove the drain plug and drain the last BIT of gas and crude out of the tank. Well,to my surprise,there was app 1/2 - 3/4 of a gallon of gas left in the tank.

So,here's the question. Should there be any gas left in the tank, when the gauge reads empty and does the gas tank pickup tube go right to the bottom of the tank. Is it calculated to leave the pickup tube slightly higher than the bottom of the tank (to prevent drawing any crude into the fuel system) or should empty be EMPTY.

On a small side note (my mind is always thinking of stupid ideas). If you were stuck on the side of the road (due to no gas) remember there might still be some gas in the tank that you could drain and jury rig a system to get you to the nearest gas station.

Gordon
Gordon Harrison

The float on the send only has a limited range, so "E" my not really be empty. Being liberal here, but if the tank was about 2 feet by 3 feet, even a quarter inch of fuel left would be about a gallon worth. The pickup tube must be pretty close to the bottom. The only tank I took apart was that of a '74 MGB. As I recall, the PU tube was very near the bottom in a recessed area of the tank. My guess is that by design the PU is higher than the drain. My thinking is that you'd only use the drain when you wanted it literally empty and therefore is designed to do so.

Although I like jury rigged gasoline-based shenanigans as much as the next guy, I'd say the time and effort required to first drain and then deliver/supply the last bit of gas to the carbs would be a waste.
Kemper

Gordon

I love these type of questions. But you have my sympathy, I ran out of fuel twice in the early days because I did not believe my fuel gauge.

I have just done a few calculations. The surface area of the tank is approx 408 square inches. The tank has a slope from back to front of 2 inches. Therefore, it requires 408 cubic inches of fuel to completely cover the bottom of the tank on a level surface. Assuming your 3/4 gallon is US measurement, this equates to to a maximum of 173 cubic inches of fuel. Give or take a bit, this means that under half the surface area of the base of your tank is covered by fuel, from a depth of 0 inches at about the mid point to a maximum of 1 inch at the front.

Now all we need is for a tank builder to tell us where the pick up point is and to what height from the bottom of the tank.

Steve
Steve Gyles

Knowing how unreliable my fuel guage is(The needle shows full until at least 3 gallons of gas have been used) I carry a graduated dip stick to verify the ammount of gas in the tank. Although this is not 100 percent accurate it is a good guide and prevents me from running out of fuel.
Dave Barron

Instead of a drain plug install a drain valve like the one on the side of the engine block. When you run out of fuel disconnect fron the sending unit and hook up to the drain valve.
Might work????
Kris Sorensen

Interesting. The Consumer Association in Britain published a back-to-back test of a Sunbeam Alpine and MGA 1600 MkII Tourer in late '61.

They found the useable capacity of the MGA fuel tank to be ten and three quarter Imperial gallons; that the fuel gauge over-read by four pints at the three-quarters full mark; was spot-on at half-full; under-read by two pints at the quarter-full mark - and showed empty when ten pints remained.

This would make perfect sense; it was BMC policy to provide a reserve sufficient for about thirty miles' motoring at what they considered would be a typical speed for the model concerned, when the fuel gauge read Empty. Thoughtful fellows.

If you can find it, the Consumer Association's test is worth reading. They gave both cars a hard time for eleven thousand miles, including two and a half thousand in a week of high-speed driving through France. After all this, the timed top speed of their MGA was 109 mph.
A. W. Risk

The fuel pickup is located 15mm above the tank floor and 125mm from the front and is between the two baffles.
jim mckenzie

With the above data, I can now assume that 1/4 full would be the best time to fill up. This would assure not running out of gas and no tank bottom crude entering the system. Thanks guys. Gordon
Gordon Harrison

I always go by mileage. 200 miles since the last fill is time to fill up with some margin left for finding fuel when in the wilds.

I always reset the trip meter when I fill up. Then I know it's time to fill both fuel and oil reservoir for the SC (that lasts about 220 miles too)
dominic clancy

Based on Jim's figures for the fuel pick up pipe, I reckon that on a level surface the MGA will cough and splutter with 0.62 US gallons or 0.52 imperial gallons (144.85 cu ins) left in the tank.

Steve
Steve Gyles

I ignore the fuel gauge and never leave home without my wife or son.
I then have no need to worry about running out of gas as I have an eco friendly reserve system ;)

I recently changed the sender unit in my tank and although it does work now I find it still moves up and down like a whores draws and declines to be reliable. I took Dominics tip and reset the trip counter.

When fitting it I had spoken to Bob West in the UK and he said that actually replacements senders are virtually all rubbish these days as the winds are not strong enough. He suggested sending the original unit for repair and can supply the name of a firm who will do it.

The replacment I did fit (the 'old' one turned out to be a replacement anyway) had the float arm set in a different position to the broken unit, could setting the accuracy be done by adjustment of the float arm?
A M Wakefield

I don't see how running the tank low will pick up any more crud than any other time.
Tom

Most crud, including water, sits beneath the fuel. Since the pickup is slightly above the bottom, it is much harder for it to pick up any contaminants.
I remember being with my grandfather, when we ran out of gas, about a mile out of town. He picked up about ten small rocks--about an inch in diameter-- and dropped them into the tank--cranked up the car and made it to the gas station. I imagine those rocks rattled around in that tank until the car finally died of old age. I guess it was common knowledge back then that the tank always had a bit of unuseable fuel in the bottom.
R. L Carleen

This thread was discussed between 08/06/2007 and 10/06/2007

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