My husband was driving our Nash on a foggy day a month or so ago and the car started backfiring like crazy, and eventually stopped running. Had to be towed home via AAA. We haven’t been able to get it to run since. It starts, but backfires like crazy, and won’t stay running. We took the suggestion of adding SeaFoam to the gas tank with the assumption that it may have water in the fuel (it has been out in the rain a number of times since being towed home) and now it doesn’t even click when we turn the key. If there is anyone out there in Car Talk land that can give us some educated suggestions it would be great. I can’t get thru on the radio’s telephone line! Thanks!
When this type of problem occurs, it usually points to the electrical system. This includes the primary electrical and secondary ignition system.
Off the bat I would replace the entire secondary ignition system components. These include the distributor cap, rotor, points, condenser, plug wires, sparkplugs, and maybe the coil. Then if this shows no improvement the primary electrical system would have to be checked for good connections.
Tester
The previous responder, Tester, is one of the many here who knows a lot more than I do. However, when I had a similar problem with my '69 Porsche 912 back in 1970-71, it turned out to be a broken valve spring (twice). I suggest that you might have a more serious problem than ignition electricals, and maybe there is a way to check before you drop a bunch of money on antique parts.
(And my 912 had a cracked head at 13K miles, and a broken speedometer cable, and a bad speedometer itself, and a too-soon worn out clutch, and body rotting out at the jack points, and… Sorry, I should not have gotten myself started about that Porsche.)
Remove the distributor cap and see if the contact points have closed up. If so, replace the points and condenser followed by putting a drop or two of distributor cam lubricant on the distributor cam lobes.
Also make sure there is no moisture inside the distributor cap.
I can’t see having a car that old, and not having a mechanic on retainer. For it to suddenly start backfiring through the carburetor, the timing may have suddenly changed. The timing chain may be excessively worn, or jumped a tooth. The spring loaded timing plate inside the distributor may have a broken spring, or the plate may be stuck. etc.
These symptoms come with a loose timing chain that has jumped a few teeth. You should be able to get the starter going again with normal procedures. If you own an antique car, then you know the procedure. For the timing chain, you line up the timing mark and check the rotor position. If there isn’t an auto mechanic in the family, take the car to one to check it out. You could also just have a bad fuel pump and a mechanic will know how to check to see if you’re getting fuel to the carb. You are asking us for “square one” info here. It would take you about six months of training before you can fix the problem or test it yourself.
Another way to check for jumped timing is to take off the valve cover and look at the rocker arms of cylinder number one, the one closest to the front on a six. Slowly turn the engine with a wrench and you will see the exhaust valve open and close and right before the exhaust is completely closed, the intake should begin to open. The short period where both valves are slightly open simultaniously is called the “overlap” period. The piston should be at top dead center in the middle of the overlap. It’s a lot faster than removing the timing cover.
Agree 100% Tester, that ‘A’ 4 pot is showing all the symptoms of ignition problems. Same engine from the Morris Minor & A35 and provided the carb is getting fuel there isn’t really much that can go dramatically wrong.
The backfiring points to fuel igniting in the exhaust system, sounds like a dead cut in the ignition maybe condenser or coil, but a service replacement of these parts along with a new set of points, rotor arm and dizzy cap is both inexpensive and probably timely.
I’d start there before worrying about the timing chain, the ‘A’ block is pretty agricultural and robust with the exception of bottom end failure due to poor oil change frequency, otherwise they go forever.
The battery probably needs a charge first though.
Two other trouble prone area on the ignition system for that engine era:
The ignition/start solenoid, this is a remote solenoid mounted on the firewall or inner fender, about 1 1/2 inches square, black bakelite with either a red or black rubber button the battery negative runs to it (positive earth) and the ignition low tension circuit plugs onto a rivetted spade terminal, that teminal can corrode and work loose, driving vibration can cause this to dead cut the ignition intermittently. The solenoid is easy to find and will be very accessible, it’ll be stamped with the makers name, Lucas…
Second point is the ignition key switch, another Lucas masterpiece mounted on the dash similar to all BMC cars of that era. Heavy bunches of keys wear these out over the years and the contacts get ‘iffy’.