First Things To Check When Your Car Will Not Start
It can be frustrating when your car won't start. Most car owners will experience a engine starting issue at least once in their driving lifetime.
This guide has easy to follow instructions, which applies to vehicles with gasoline burning engines.
If your car is not cranking over then you have a different problem and you
need to follow this guide instead:
to do when your engine is not cranking over
If it seems like the car is hard starting because its taking an abnormal amount of time to catch and run
then you need to follow this guide:
How to repair a hard starting engine
What makes an engine run?
For an engine to run it must have compression, the proper amount of fuel and air
mixture with a spark at the plug at the correct time. Check out the video below to get an
idea of what needs to happen inside in each of the cylinders for the engine to
Test Vital System Fuses
Fuses are used to protect various electrical circuits while supplying power
to components such as the fuel pump, injection and computer systems from suffering a short
circuit and possibly causing an electrical fire. When these fuses blow the system they
support stops working and the engine stops running.
When a fuse blows it does so for one of three reasons.
There is an electrical surge in charging system or the battery has been jumped backwards
The fuse ages and pops
A short circuit exists because a wire, sensor, amplifier or computer has shorted to ground
Learn more: How to check electrical fuses
There are two methods of checking electrical fuses that protect various
components, you can either pull each fuse out and inspect it by hand or use a
test light and check its continuity. If a blown fuse is found check the system it belongs to by
using the vehicles owner's manual or the identification chart on the fuse panel
cover. Once the system is identified remove and inspect or replace the failed
part and retry the engine. If the fuse still blows you will need to check the
wiring harness for damage or a broken wire and repair it.
Check For A Crankshaft Angle Sensor Failure (P0335)
The crankshaft angle sensor is responsible for sending feedback data to the main
computer which in turn translates it into usable information which controls the
injector pulse and ignition timing. When this sensor fails the computer see's
the engine as not turning which in turn will not send pulse signals to either
fuel or ignition systems. This problem causes the engine to crank over but not run.
This sensor is subject to heat and engine vibrations and is
inexpensively produced in mass qualities creating high failure rates. When
this sensor becomes worn or weak it will fail to produce the alternating
currant needed for the computer to read.
Learn More: How to replace a crankshaft angle sensor
These sensors are located either at the front, middle or rear
of the engine near the bottom of the block where the crankshaft resides. Replacement takes
about 45 minutes give for take depending on location and the accessories
that maybe needed to be removed to perform the repair.
Test the Fuel Delivery System
The fuel system is used to deliver the proper amount
of fuel at the correct time of the cylinder's compression cycle. This is performed by the
injection system which consists of a fuel injector for each cylinder, a fuel
pump which is located in the fuel tank and fuel lines that travel from the tank and head up to
the engine and into the fuel rail where the fuel injectors reside. This entire system
is controlled by the computer; if there is a malfunction the electronic injector
drivers inside the computer will not send a trigger signal to allow fuel to enter the engine.
If fuel is not entering the cylinder's combustion chamber the engine will not
run and deliver the individual cylinder power as intended. This could be due to a fuel pump that
has failed and is not supplying fuel pressure, or the injectors themselves are not operating
correctly allowing the proper amount of fuel to be distributed into each
cylinder for the piston to ignite.
A fuel pump is a basic electrical motor that is subject to vibration and can fail due to wear and usage. These pumps are cheaply mass produced which
increases the risk of them not working. A fuel injector is simple magnetic on
and off valve that is controlled by an electrical pulse supplied by the main
computer. These units are subject to heat, engine vibration and fuel
impurities such as gunk and dirt that can make them clog. If one of them short
circuits it can cause the injector driver to "lock up" not allowing any of the
injectors or fuel pump to operate.
Learn more: How to test a fuel pump
The easiest way to check if the fuel pump is turning on is to
be very quite and switch the ignition key to the on position without
cranking the starter. You should be able to hear the pump running in the
rear of the car. If you are unsure of its operation then you will need to
test the fuel pressure. If no pressure is present then confirm the fuel pump
being bad by using a wring diagram for your vehicle and probing the pump
power wire using a test light.
If the fuel pump electrical system and pressure seem to be working okay the next step
is to test the injector pulse. This can be done by using a test light while the
engine is cranking over to see if the injector is getting a trigger signal from
Learn more: How to test a fuel injector
Test The Ignition System
The ignition system is designed to ignite the fuel air mixture inside
the combustion chamber via the spark plugs. This is done by using an ignition coil,
a crankshaft and camshaft angle sensor along with the car's computer or PCM (Power
Control Module). This system can stop working due to a failed ignition module or the
angle sensor which is very common.
Ignition components are subject to heat and the vibration of
the engine along with the constant wear of building an electronic field and
then releasing it to amplify the voltage needed (25,000 to 35,000 volts) to
bridge the spark plug gap which ignites the fuel. When spark plugs wear they
cause this voltage to build higher then the coils and the ignition system is
designed for which creates a
failure by overheating.
Learn More: How to Test the ignition
Testing the ignition system is an easy job that takes about 5 minutes and can be
done using a test light or an extra spark plug. Connect a test light to ground
and with one of the spark plug wires or coils disconnected. Crank the engine
over while holding the tip of the test light about 1/4 (7mm) inch from the
wire or coil terminal. Keep your hands clear of the test area to avoid an
accidental shock. You can also insert a spark plug into the coil or wire and
hold it against a metal ground. You should see a light blue spark in the
gap, this is telling you the system is working. If no spark is present more
testing of the system will need to be done.
Check the Cylinder Compression
For an engine to work three things are needed to happen inside it's cylinders to crank over
and run; compression, fuel and ignition. Cylinder compression is the result of
the proper correlation of the crankshaft, camshaft and valve system while the
pistons travel upward in the cylinder bore. When the volume of compression drops below about 85 psi
combustion is not possible.
Cylinder pressure can be affected by a mis-alignment of the crankshaft and
camshaft that can put the valve timing out of sync with the pistons. The most common cause for
this is a jumped timing belt or timing chain. Improper maintenance such as not changing the oil and filter can cause premature
wear of chain where as the belt is a regular service item that should be replaced between 70,000 and 90,000 miles.
Learn More: Testing Engine Compression
Checking engine compression is not too difficult and can be done with
a spark plug socket and a compression gauge. Remove the ignition or fuel pump fuse and one of the easiest
spark plugs to perform the test. If compression readings are between 125 and 170 psi
the compression is normal. Most of the time if one cylinder has the correct compression
the engine will start and run, if one or more cylinders have low compression the
engine will misfire
and have a rough
idle but still run. When the compression is low or non-existent the engine will crank over
freely with little resistance to the starter a sure sign the chain or belt is a
Read The Engine Trouble Codes
When a vital sensors or controllers fail in the engine computer system such as a crankshaft angle
sensor, ignition amplifier or fuel pump controller it will stop the engine from starting. This is because the
engine needs spark at the time of
compression and fuel to enter the combustion chamber to run.
A computer sensor, electronic controller or amplifier is exposed to heat and vibration which
can cause the internal workings of the unit to stop operating. These failures include
an open or short circuit in the electrical part of the sensor making it non-operative.
Learn More: How to read trouble codes
A check engine, service engine soon or MIL is telling you there is a
diagnostic trouble code stored in the car's computer. These
are designed to give you an idea of the system or sensor that is causing the
engine not to start. When these codes are present it means the computer has
detected a failure which when corrected can fix the trouble. Today's cars are easier
than ever to read the codes and it doesn't cost much for a code reader if you
don't have one from places like Amazon. Plug a code reader tool or scanner into the ALDL port which is
located on the driver's side near the bottom of the dash in most cases and gather any
codes that are present.
More Obscure Starting Issues
There a few subsequent conditions which are more difficult to detect which will cause your engine not the start and run such as:
Water in the fuel tank
Electrical system wiring harness failure
Car was driven through a deep water puddle causing electrical components to get wet.
Before your car wouldn't start did you notice anything out of the ordinary
while it was still running such as low power or the check engine light on? This could aid in the troubleshooting and diagnosis
of the problem. If you are taking your car in for repairs, be sure to mention anything you noticed before the
trouble began to your mechanic.
Got Any Questions?
Check out our
engine not starting forum
if you have questions. Our community would love to help you. Most of us are
mechanics by trade and will answer any question you might have.