So, your engine won’t start?
Image: aresauburn 2009
Here's a checklist, and some information to help, outlining the various things that could be preventing your classic car engine from starting.
Due to open primary ignition circuit
- Burned or oxidized ignition points.
- Ignition coil resistance unit burned out or open.
- Starting switch ignition coil resistance by-pass circuit open.
- Ignition points not closing.
- Breaker arm binding on pivot post, preventing closing of points.
- Breaker arm spring weak or broken.
- Breaker arm disported or bent.
- Dirty ignition points.
- Primary windings I coil broken.
- Open ignition switch circuit.
Due to ground primary ignition circuit
A grounded coil primary winding, a grounded ignition switch, or a grounded switch-to-coil primary lead will cause excessive current flow and will usually cause wires to burn.
- Ignition points opening or closing due to improper adjustment.
- Ignition points not opening due to worn rubbing block on breaker arm.
- Faulty insulating bushing in breaker arm.
- Cracked or worn faulty insulator at distributor primary terminal.
- Grounded condenser.
- Distributor-to-coil lead grounded.
- Primary coil winging grounded.
Due to faulty secondary ignition circuit
- Corroded sparkplug cable terminals.
- Chafed or cracked insulation on cables.
- Ignition coil weak or inoperative.
- Moisture on ignition coil, terminals, distributor cover, spark plug porcelains, or in distributor.
- Improper type of spark plugs.
- Cracked distributor cap or a burned carbon track from distributor cap center terminal to distributor housing.
- Improper installation of spark plug cables (not correct for engine firing order).
- Spark plugs damaged, dirty or wet, porcelains cracked, or gaps improperly spaced.
- Rotor contact spring bent or broken.
- Distributor rotor grounded.
- Distributor cap center terminal (inner) broken or missing.
- Broken or burned out radio suppressor in distributor cap.
Due to battery
- Battery run down.
- Terminals loose or badly corroded.
- Improper ground.
- Battery cables frayed or undersize.
Due to starter motor
- Not operating properly.
- Congealed engine oil fur to use of too heavy grade of oil or to the formation of sludge.
- Starter gear binding in flywheel gear.
- Defective starter switch.
- Faulty neutral safety switch on cars with automatic transmission.
Due to excessive fuel supply (flooding)
The engine is said to be flooded with fuel when a quantity of liquid fuel collects in the intake manifold, and perhaps also in the cylinders. This condition gives a mixture that is much too rich to ignite.
If the carburetor has a provision for opening the choke valve when the throttle is fully open, crank the engine with the throttle open until engine starts. It will start as soon as the extra fuel is pumped out.
If the choke valve is not designed to open when the throttle if fully open, tie or block the choke valve open and crank the engine until it starts.
Flooding may also occur on the road. If the carburetor supplies too rich a mixture at full throttle, the intake manifold may be flooded with liquid fuel, with the result that when the engine is stopped, heat evaporates the fuel and thus provides an over-rich incombustible mixture. The engine won't start until the rich mixture is pumped out by cranking.
- Choke not operating properly.
- Automatic choke not properly set.
- Carburetor unloader linkage (if equipped) not properly set.
- Float level set to high.
- Dirty, worn or faulty needle valve and seat.
- Float sticking or rubbing against side of fuel bowl.
- Leak in float, allowing fuel to get inside.
- Fuel pump pressure too great.
Due to insufficient fuel supply
- Carburetor inlet needle stuck in its seat, due to gum in fuel.
- Float level too low.
- Clogging inlet screen at carburetor.
- Faulty fuel pump or one of insufficient capacity.
- Fuel pump strainer clogged.
- Faulty fuel pump bowl gasket.
- Flexible line (if used) twisted, deteriorated or restricted.
- Fuel line to tank clogged, kinked, restricted or leaking.
- Vent in fuel tank filler cap clogged or restricted.
- Worn fuel pump camshaft lobe.