This article is going to be a catch-all for a variety of problems that can kill your engine when you are not out of fuel.

On 7/26/2021, J. D. Sutcliffe in Canada wrote:
"I found it odd that I ran out of gas because by my rough estimation I still had lots of gas".

Obviously you didn't run out of gas, but you have a fuel delivery problem. There are a few possible issues.

First, some trash in the fuel tank that will obstruct the pick-up pipe. MGA has a non-filtered open-end pickup pipe, so it takes quite a large piece of trash to clog that up. A little piece of foil seal that came off the top of a fuel additive bottle could do it. When you stop and add fuel to the tank, the sloshing will wash the obstruction away from the pipe, and it can run well for a while, until the obstruction gets stuck on the pipe again. This is more likely to happen when fuel level is lower.

Solution is to drain the tank to see what comes out, run the fuel through a paint filter to see how much trash is in it. After filtering, put the fuel back in the tank and drain again to rinse, filter, and repeat until you're sure there is no trash left in the tank. This is more effective if you remove the tank so you can shake it to rinse well inside.

There might also be enough rust in the tank to clog up the coarse screen filters in the car. Check the filter in the (original style) SU fuel pump. Remove plug in bottom to extract a screen the size of your pinky finger. Rinse and reinstall the screen. There are also smaller screens about the size of a thimble at the carburetor float chamber inlet ports. Remove the fuel hose connection banjo bolt to extract these screens. Also look for dirt in the bottom of the float chambers where it can plug up the drill hole going through the lower arm to the banjo bolt (or banjo stud) on bottom of carburetor.

When in doubt, or not wanting to remove the fuel tank, you can install an in-line fuel filter in the hose in engine bay between fuel feed metal pipe and the rear carburetor banjo fitting. This will not stop upstream clogs, but it can stop rust from getting into the carburetors. If the filter gets clogged, replace the filter. If the filter gets clogged quickly, then too much rust in the fuel tank, so you need to clean or replace the fuel tank.

Rubber grommets on the banjo bolt on bottom of carburetor commonly deteriorate, which often leads to a fuel leak. Deteriorating rubber grommets can also clog up the cross drilled hole in the banjo bolt, stopping fuel from getting into the main jet, which will result in running (very roughly) on two cylinders, easy stalling from idle speed, and hard to get started again. For this you need to replace the rubber grommets. Moss Motors (and some other vendors) now sell these grommets made of Viton elastomer, which is highly fuel resistant and will last a long time.

Some older fuel hoses may also deteriorate when using 10% alcohol fuel. They can plug up inside, or shed bits of rotten rubber to clog up a fuel valve downstream. By now these old hoses should all be off the market and gone, so any new hoses will be alcohol resistant.

Carburetors do not like 10% gasohol fuel. Gasoline boils at 190dF. Alcohol boils at 160dF. Gasoline and alcohol make a mixture, not a chemical compound. This means you can boil the mixture at 160dF, and distill the alcohol out of the mixture. It also means that gasohol boils at 160dF. No problem while cruising down the road with lots of air flow and lots of fuel flow cooling the carburetors. But if you slow down to a stop and go or idle speed creeping situation, or idling while standing still on a hot day, the fuel can boil in the carburetors. Resulting bubbles getting into the main jets make the fuel mixture go lean, causing rough running and tendency to stall, and difficulty re-starting.

Temporary solution is to pull the choke to enrich fuel mixture, making it run better (and faster idle as well), which can get you through the situation until you get moving again. If you shut it off for a fuel stop when hot (220dF on the temperature gauge), it will not restart five minutes later. Solution then is full choke and full throttle while cranking until it starts. Kind of counter-intuitive to have to choke it when it is hot.

You could try to always use non-alcohol fuel, but that is often impractical. You can easily install a bilge blower ($20 part and 20-minute installation) in the air pipe in front of the carburetors to blow cool air on the carbs, which can give a HUGH improvement in carburetor cooling, and may entirely eliminate the hot carburetor and fuel boiling problem. You only need to run the bilge blower during those hot running conditions that could cause boiling alcohol.

Common failure mode of an ignition coil is to fail when hot, then work again after cooling down. This only gets worse with time, fails more often (an earlier), takes longer to cool down. You can detect loss of spark when it dies and will not restart. Sometimes you can diagnose a failing ignition coil with an ohm meter showing open circuit in either primary or secondary winding. Solution is to replace the coil.

. We have had a rash of bad condensers in recent years (at least 10 years now), and this is not improving any time soon. A condenser might be bad right out of the box, or might fail any time from a few days to a few months down the road. Solution is to change the condenser, and do try to find a source for good condensers.

Inside the original style carburetor (or any carburetor with a vacuum advance unit), there will be two flex wires. One goes from the side stud to the contact points (and condenser connection). The other flex wire goes from the moving contact plate to the distributor housing for certain grounding connection. If one of these wires breaks, it can cause intermittent connection (intermittent spark). This connection often comes and goes relative to throttle position (vacuum signal level). The connection might be good when is off or idling, difficult to diagnose. For this you need to disconnect the wire, then use a continuity tester (test light or ohm meter or beeper) to check for continuity while you flex and straighten (pull and push) to see if it breaks the connection when moving. Solution is to replace the flex wire.

Lots here to check and test. Hope something here helps you find and fix it.