Description: An engine should start up and run in about 2 to 3 seconds of
turning the ignition key to the crank over position, if not you have a hard
starting condition. This guide will help by starting with simple fixes and
conclude with the more difficult.
What goes wrong?
Normal wear and usage can cause a hard start condition due to lack of
fuel pressure, poor intake air management, false readings to the car's computer
or weak spark. Some of these repairs are simple and are included in the normal
maintenance of the engine. This can sound complicated, but it really isn't,
today's vehicles are easier than ever to repair thanks to the vehicle’s computer
control system and basic troubleshooting methods.
What will it cost?
This amount will vary because of the range of variance between repairs.
Some jobs are inexpensive such as a throttle bore service which will cost about
$15.00 if done at home and it can go as high as $450.00 if a fuel pump is bad
and replaced by a shop. Either way it's best to have an idea of what's wrong
before you start the repair, or when you are taking your car in for repairs.
Popular Hard Starting Causes
- Torn air intake boot
- Weak fuel pump
- Dirty throttle bore
- Worn out spark plugs
- Bad engine temperature coolant sensor
- Low cylinder compression
- Check engine light
- Misreading MAF sensor
Let's get started
This guide pertains to most cars, configurations maybe slightly different but
the process is the same.
The Easy Stuff
- If you noticed the check engine or service engine soon light there maybe
a trouble code that will help us pinpoint the issue. First
run the codes and see what they pertain too, we can then troubleshoot
and go from there such as a lean mixture code which can point at a weak fuel
pump, a bad MAF sensor (mass air flow) or cracked air intake boot.
- An engine vacuum
leak can cause extended crank times and low or rough idle and possibly a
check engine light. A visual inspection of all vacuum lines inside the
engine bay you may discover a broken, torn or dilapidated hose that needs
replacing and for harder to find leak a smoke tester can be used or when the
engine is cold a can of carburetor cleaner which will cause the engine to
idle normal or speed up for a brief period.
- Normal service items: Prolonged cranking can be caused by a dirty
throttle bore which can disrupt the airflow into the engine. The throttle
actuator (throttle bore on older vehicle - cable) is an electronic throttle control
which will get a condition called "coking"
which is a kind of light tar like goo on the butterfly and its inner body. This
substance is due to the impurities in the air the engine consumes over many
miles. This simple service
can be done with minor tools, no parts are needed just a shop towel and a
can of carburetor cleaner which you can get at Amazon or any auto parts
- Torn or cracked air intake boot or tube. The
air tube or boot is
mounted between the throttle bore and MAF sensor can be cracked allowing air
to enter the engine that is not monitored creating a
lean mixture. If this tube or boot is broken or torn it will alter
reading therefore feeding the computer false information causing an extended
crank time for the engine. To check for this problem remove the air intake
tube and inspect it, replace the worn, torn or broken parts as needed.
- Some car and most trucks have a
fuel filter located
between the fuel pump and the engine and when this filter clogs it causes
the pump to labor causing low fuel pressure or slow to pressure the fuel
rail allowing the injectors to deliver too little fuel.
- The engine's MAF sensor can cause a mixture issue and a slow to run
condition due to a contaminated internal sensor wire. Sometimes this can be
cleaned by performing a MAF
service which involves minor tools and can of MAF cleaner.
- Engine's equipped with an idle air control motor (IAC - older cars) will
need to clean this valve
much like a throttle bore. To test for this before you turn the engine over rest your foot on the gas pedal slightly to open the
butterfly. This will bypass the idle air control valve and allow the engine to
start. If the engine starts by resting your foot on the gas pedal remove the IAC
and clean it, again no parts involved just a shop towel and carburetor
- Slow to crank over: An engine needs a minimum cranking speed to start if
the starter or battery is weak the engine cranking RPM will be low which
causes the engine to build compression slower and make it harder to start.
This can be caused by a weak
battery or starter
- As a fuel pump ages the pressure provided can be less that adequate to
run the engine correctly. This can be tested
fuel pressure gauge which can be obtained at your local auto parts store
(for free in most cases). Most fuel pressure systems will be between 45 and
60 psi. (port injection) if found to be low the
fuel pump must be
- Once a MAF sensor has been cleaned once it rarely helps twice, at this
point the MAF
sensor should be replaced, this can be confirmed by using a scan tool
and reading the intake air GPS (grams per second) between the new sensor and
- Spark plugs are a
normal maintenance item and if you have not replaced
them and your car's odometer says over 50,000 miles, it's time. On most cars this
job is simple and can be done within an hour or so, the only parts you need are
the spark plugs which play a role on how the engine starts and runs. You can get
spark plugs from
Amazon or an auto parts store.
- Typically on high mileage engines (200k to 300k) the pistons rings
can wear causing low compression which increases crank time and causes
low power. This is
because the compression ratio is low and it takes momentum for the engine to gain enough
speed to ignite the fuel air mixture. To check for this
compression test is needed, if the compression is 90 psi or lower the engine
is worn out and to be more specific, the pistons rings no longer seal
against the cylinder walls and need to be replaced. Basically you need to
rebuild or get a rebuild engine, this video shows
how to replace the piston rings and
Our team of certified mechanics is ready to answer your questions for free.
Article published 2021-07-28