What to Do When Your Car Won't Start

by Larry Johnston

Vehicles are so reliable today that we pretty much take it for granted that the car's going to start whenever we're ready to go. Sometimes that doesn't happen, though. Either the starter doesn't crank at all or it cranks, but the engine doesn't start. Here are some tips for dealing with those situations.

Starting: The Big Picture

An internal combustion engine requires three things to run: fuel, compression and ignition:

Fuel for a gasoline automobile engine gas is mixed with air by the fuel-injection system (carburetor on old cars) in the ratio of 1 pound of gas to about 15 pounds of air. It flows into an engine cylinder through the open intake valve as the piston moves downward.
The piston compresses the fuel as it moves back to the top of its stroke with the intake and exhaust valves closed.
Ignition occurs when electricity arcs between the spark plug electrodes at the top of the compression stroke.

When all that happens, you're off and running. Lose just one element, and you're stranded.

Car Doesn't Crank at All

If you turn the key and nothing happens, the problem may lie with the battery, starter or associated components. Here are some common faults:

Open safety switch — clutch isn't fully depressed or automatic transmission lever isn't in Park (P) or Neutral (N)
Dirty, corroded or loose battery connections
Dead battery
Loose connection or broken wire in starter circuit or faulty starter switch
Defective starter motor or solenoid

What You Can Do

Move the shift selector out of and back into P or N a couple of times or pump the clutch pedal a few times, and try starting again.
If there's still no response, turn on the car lights. If they're dim, you may have poor battery connections or a weak battery.
Clean and tighten the battery connections; if that doesn't help, hook up a battery charger or try to jump-start the car.
If charging the battery or jumping starts the car, have the battery and charging system tested.
If the engine still won't crank, troubleshoot the starting system with test equipment.

Car Cranks but Doesn't Start

If the starter turns but the engine won't start, finding the problem usually requires troubleshooting with test equipment. (If the engine cranks slowly, see Car Doesn't Crank at All, above.) Fuel or ignition malfunctions cause most non-starts; compression loss often results from engine wear or damage. Here are some possible fuel and ignition problems:

Empty gas tank
Blown fuse for fuel pump
Wet or damaged spark plug wires
Faulty fuel injectors or system sensors
Defective ignition coil or wiring

What You Can Do

Make sure there's gas in the tank.
Check fuses for fuel pump and engine controls (see owner's manual for locations).
Dry off ignition components if wet; replace damaged spark plug wires.
Look under the hood for loose wiring connectors at fuel injection and ignition components.
Have a qualified technician troubleshoot the car with test equipment.

In five decades or so of tinkering with cars, freelance writer Larry Johnston has learned that cursing at one isn't enough to make it start.