How to Troubleshoot Starting Problems on Vehiclesby Contributing WriterUpdated June 12, 2017
There are three basic elements involved when trying to start any internal combustion engine, and motorcycles are no exception. First is fuel, second is fire -- or rather, electricity -- and last is air. If the engine isn't getting enough of any of these elements, it won't start. In most situations, if you run through a short checklist of potential causes, you will find your problem -- and usually be able to fix it without spending a cent.
Under The Hood:
- How to Troubleshoot Starting Problems on a Ford Ranger
- How to Troubleshoot Starting Problems on a 2002 Honda Shadow Aero
- How to Troubleshoot Starting Problems on a 1999 GMC Sierra
Crank the engine. If the engine cranks faster than normal and won't start, then your starter is likely failing and requires replacement by a professional mechanic.
Check for a flooded engine. Crank the engine. If it cranks normally, and if there is a strong fuel smell in the engine bay but no fuel leaks, then your engine may be flooded with gasoline. This is symptomatic of an air-to-fuel mixture problem. Probable causes are a bad mass air flow sensor or a sticking throttle valve. The entire intake system should be cleaned by a professional mechanic.
Pull a spark plug wire off the top of the engine. It should pull right off, but you might have to wiggle it a little as you are pulling up on it.
Remove the spark plug as follows. Attach the spark plug socket to the extension and lower it into the spark plug well. Turn the spark plug counterclockwise to loosen and remove it.
Pull the spark plug out of the plug well and remove it from the socket. Insert the spark plug into the end of the spark plug wire so that the electrodes are facing out (the orientation is the same as when the spark plug was in the engine).
Crank the engine and have an assistant check for spark on the spark plugs.
Repeat Steps 3-6 for each spark plug. If there is no spark on any of the plugs, then your problem is a bad spark plug, plug wire or distributor. To verify whether the problem is the plugs and wires, remove the plug wire at the distributor end and crank the engine. You should see a small, but solid, blue spark jump to a metal part of the engine. If there is no spark, then you need to replace the distributor. If there is a spark at the distributor, then you'll need to replace the spark plugs and wires.
Items you will need
Spark plug socket
Socket wrench extension
Check the choke lever. If it is disengaged, pull the lever down until you feel resistance. Try to start the bike.
Check the fuel petcock. Make sure that it is turned to the "On" position. With the choke still engaged, try to start the bike again.
Check how much fuel you have. Add fuel to the tank, and try again.
Check the spark plug cables. Make sure they are properly seated. Try to start the bike again.
Remove the battery cover. Use a voltmeter to check the charge of the bike. It should be around 12 volts.
If the charge is low, try to jump the bike off of another battery. Any car or truck will do. Alternatively, you could use a plug-in jump starter instead.
If the bike starts while being jumped, disconnect the jumper cables. If the bike stays running, you should replace your battery. If it dies you may need to replace the alternator. If the bike doesn't start, go to the next step.
Check the spark plugs. Remove them, and check for signs of wear or damage. If they are damaged replace them. Remember, even though a Honda Shadow only has two cylinders, you still need to replace all four spark plugs. If they appear operable, go to the next step.
Connect the spark plug to the spark plug cable. Touch the spark plug to the frame or engine block. Push the starter button, while watching the spark plug. If you see a spark, the plugs are working, and your problem lies elsewhere. If there is no spark, renew your spark plug cables and coils. If that still does not fix the problem, you need to take the bike to a shop.
Make sure that your gas tank is full.
Disconnect the fuel cable from the fuel petcock. Turn the petcock to the "On" position and then quickly back to "Off." If fuel comes out, your petcock is in working order. If not, replace it.
Remove one spark plug from each cylinder, and wait for approximately one hour.
Replace the spark plugs and attempt to start the bike again. This will clear any flooding that may have occurred in the process of trying to start the bike.
Remove the seat from the bike.
Remove the air filter cover.
Check the air filter. If it is gray or dark brown, or if there is debris caught inside of it, replace it. If it is clean, put it back in place. Attempt to start the bike again.
If the bike still won't start after checking everything, you will need to take it to a mechanic.
Items you will need
Set of metric socket wrenches
Spark plugs (4)
Attempt to start the vehicle. If it starts with difficulty, check to see if the check engine light is on, indicating a computer control or sensor problem. Listen for the starter to energize as you attempt to start the engine. If the engine turns over when the starter is energized, the problem is not with the starter. If it fails to energize and no sound can be heard, the problem is electrical.
Plug the code scanner into the OBD port under the left side of the steering column. Turn the key to the run position. Press the “Read” key on the code scanner. Make a note of the code displayed on the scanner, and cross reference this code with the accompanying code sheet for a definition of the problem. Repair the problem and reset the computer by pressing the “Erase” key.
Check the battery for the proper voltage. Connect the voltmeter’s black lead to the negative battery terminal and the red lead to the positive battery terminal. The voltmeter should display 12.75 volts or very close. If it does not show 12.2 volts or higher, start the engine and re-check the voltage to see if the alternator is functioning. With the engine started, the voltage should rise to between 13.8 and 14.5 volts. If it does not rise, the alternator is bad--shut the engine off.
Have a helper start the engine while you watch the voltmeter. If the voltage drops below 10.5 volts when the engine is started, the battery has a bad cell and must be replaced.
Check the starter fuse in the fuse relay box on the driver’s side fenderwell if the starter does not energize. If the fuse is good, check the terminals on the battery for corrosion or looseness, repair as necessary and try the starter again. Check the starter for battery power at the large-diameter wire terminal on the starter solenoid by placing the voltmeter’s black lead on a good ground and probing the terminal on the solenoid where the large diameter wire is connected. The voltmeter should show battery voltage. If not, the problem is the wire or battery terminal.
Check the small diameter wire on the solenoid, which is the ignition switch wire. This wire should have power only when the key is in the start position. Have a helper turn the key to start, and probe the small wire for power. If it has power the starter is bad. If there is no power the ignition key is bad.
Check the engine for fuel starvation. Take the gas cap off and listen for the fuel pump to energize when a helper turns the key to the run position. The fuel pump will only run for 2 seconds at a time if the engine is not started. Cycle the key on and off in 5-second increments. If you cannot hear the fuel pump, check the fuel pump fuse located in the fuse relay box under the hood. If it is good, remove the air duct at the throttle body using a screwdriver.
Open the throttle by pushing the linkage with your hand, then spray a 3-second shot of carburetor cleaner into the throttle body. Install the air duct temporarily on the throttle body. Try to start the truck. If the truck starts and runs for a second or two where it wouldn’t previously, the fuel pump is bad. If it does not run, the problem is elsewhere.
Check for water in the oil. Look at the dipstick and see if it looks like mud (oil mixed with water) as a result of a blown head gasket. Remove the oil cap and check for the same thing. Remove the radiator cap and look for oil in the antifreeze. If oil is found in any of these locations, the head gasket must be replaced.
Remove a spark plug wire from the spark plug and insert the spare spark plug. Lay the spark plug on the intake manifold with the electrode touching a good ground. Have a helper crank the engine while you watch the spark plug. When the engine is cranking, a blue spark should be visible at the electrode. If no spark is evident the problem is in the ignition circuit.
Check the coil for power at the positive terminal. Connect the voltmeter’s black lead to a good ground and probe the positive side of the coil with the red lead. With the key in the run position there should be battery voltage at the coil. If there is no voltage a wiring problem is present. If it does have power, either the coil or spark plug wires are faulty.
Check the coil wire for continuity. Place the volt/ohmmeter into the ohm mode. Place the black lead on one end of the wire and the red lead on the other. There should be no more than 18,000 ohms. If the resistance is higher, replace the plug wires, including the coil wire.
Items you will need
Can of carburetor cleaner
Fuel pressure tester
Small pocket screwdriver
Spare spark plug