Simple steps to get your classic running again

By Carl Heideman
Oct 23, 2023

To run, a car only needs fuel and spark–although that spark has to occur at roughly the right time. To repair most breakdowns, you just need some simple hand tools, a friend and a 12-volt test light.
Most breakdowns are caused by an ignition problem.Step 1: Try to park in a safe, dry place.

Step 2: Pull a spark plug and ground its threads on the block to see if you have spark. An assistant needs to crank the starter.

Step 3: If there is a spark, move to the fuel system. If no spark, check whether you’re getting spark from the coil to the distributor. Pull the coil wire from the distributor and hold it near a ground. Again, have your assistant crank the starter. Look for spark from the coil lead. Note: Coils are blamed for most ignition problems but seldom are the culprit.

Step 4: If you have spark at the coil lead, you likely have a problem with your distributor rotor or cap. Carry replacements. In recent years, rotor problems have been much more common than car problems, so start with a rotor.

If you don’t have spark from the coil lead, then you’ll need your test light. Attach the ground clip of the light to a good ground, then touch the point to the positive side of the coil while the ignition switch is turned on. (This is assuming a negative-ground car.)

The light should glow. If not, trace this part of the ignition circuit to determine why the coil isn’t getting power. Notes: For positive-ground cars, switch the polar- ity on this test procedure. The coil is marked with a + and – on either side where the wires attach.

Step 5: Does the ignition switching mechanism work? Assuming you have power to the coil, hold the pointer of your light to the negative side of the coil while your assistant cranks the engine. Your light should flash on and off as the engine spins over, telling you that the switching mechanism in the distributor is working. (This is true whether the car has points or an electronic ignition.)

If the light glows steady or not at all, it’s time to get into the distributor. If working with a positive-ground car, don’t forget to switch the polarity on this test procedure as well.

To determine why your distributor isn’t providing the switching for the coil, you’ll need to get out the manual for your car (or your ignition system if it’s aftermarket) to go through the testing procedure for your points or electronic switching mechanism.

If it’s not an ignition problem, then it’s likely a fuel delivery issue

Step 1: Make sure that the throttle linkage hasn’t become disconnect- ed or fouled up.

Step 2: If you have an electric fuel pump, determine if it’s working or not. Note: Mechanical fuel pumps seldom fail while en route. If the fuel pump is working, proceed to Step 4.

Step 3: If the fuel pump is not working, then make sure its fuse is good and check that neither the positive nor negative wires have become disconnected, pinched or pulled off.

Step 4: Check that fuel is getting to the carburetor or fuel injection. Fuel is pressurized to 3-5 psi on a carbureted car and upward of 35-40 psi on a fuel-injected car. DO NOT ALLOW FUEL TO SPRAY ON A HOT ENGINE OR ANY OTHER HOT COMPONENTS. Carefully pull the fuel line off the carburetor or injection. Aim the line at a suitable catch can. Have an assistant crank the engine. If fuel comes out of the line, then you have a carburetor or fuel injection issue and should proceed to Step 6.

Step 5: Check your fuel filter. If you can blow through the filter, then you might have a clog elsewhere in the delivery system. Follow the fuel system back to a possible second fil- ter and finally the tank. Sometimes the tank’s pickup can get clogged, and you can remove the blockage by either blowing back through the outlet tube or running a rod or piece of wire through the tube. Be prepared to reattach the line very quickly, and remember that fuel and its vapors are very flammable. Do not work with fuel around hot engines, hot exhaust systems or other hot components.

Step 6: Some carburetors, like Webers, pass the incoming fuel through a screen. These screens can get clogged but are easily cleaned.

Step 7: Car still not running? Now that you’ve ruled out all of usual culprits, you have to delve deeper. On a carbureted engine, it could be a sunk float or a clogged jet. On an injected car, you might have a disconnected crank angle sensor, clogged fuel injector or another failed or disconnected electrical component. Check all grounds, too.