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Troubleshooting
/ Engine
Cranks Excessive
Engine Cranks Excessively
Troubleshooting Procedure
(Definition: the key is turned and the engine is cranking, but it takes longer than
usual before the
engine
to start running.)A. Testing Fuel Pressure: Test for proper fuel pressure with a test gauge
on the fuel rail, most
throttle
body injection cars (TBI) are between 13 psi and 17 psi. Most (DPI) direct
port inject systems are between 40 psi and 55 psi. If little or no fuel pressure
is observed and there is
12 volt power
present at the fuel pump, the fuel pump has failed and needs replacing.
B. Test for Fuel System Pressure Bleed Down: With a fuel pressure gauge connected
to the fuel rail, turn the key to the on position without starting the
engine.
You should observe the fuel pressure gauge jump up quickly to operating pressure.
Then turn the key off, if the gauge pressure falls quickly it is a sign of a failing
fuel pump. Next check the fuel injectors; if the nozzle valve inside of the fuel
injector is failing it can cause excess fuel to leak inside the engine causing a
rich, hard starting condition.
C. Test Idle Air Control Motor (IAC) An idle air control motor adjusts the
amount of air released into the engine when the engine is at idle. This air
controller is monitored and adjusted as needed by the ECM. As car mileage
increases the IAC motor is subjected to mass amounts of air which contain
impurities that leave deposits that can slow or stop the operation of the IAC
motor. To check for this condition remove the IAC motor and inspect, if the
plunger of the motor has deposits, clean or replace the motor with a new unit.
(Note: clean the air passenger ways with an aerosol cleaner before installing
the new idle air control motor.)
D. Inspect for Vacuum Leaks: Inspect your
engine
vacuum hoses and air intake boot for tears or ruptures. If vacuum from the engine is allowed to leak
it will cause a lean mixture causing the engine to crank excessively before start
up, replace any broken or cracked vacuum lines with new and recheck system.
Failed Air Intake Boot
E. Check Air Intake Boot: Inspect the air intake boot from the throttle body
to the mass air flow meter. If torn or broken it will allow the engine to have a
lean fuel/air mixture causing excessive cranking. Replace the air intake boot and
recheck system.
F. Test for Faulty Fuel Pressure Regulator: If a fuel pressure regulator diagram
ruptures it can allow raw fuel into the
engine
through the vacuum feed line attached to the intake manifold. To check for this
condition remove the vacuum line from the regulator and check for the presence of
fuel inside the vacuum line, if fuel is present replace the fuel pressure regulator.
G. Test for Low Compression. (For high mileage engines only) Remove
a spark plug, insert compression gauge and test. The
engine
compression should be above 115 p.s.i. if not, the engine with crank longer
before enough compression can be generated for ignition.
For exact specific repair procedures for any of the steps above visit our
online repair
manual page.
Troubleshooting
/ Engine
Cranks Excessive
Check Manufacturer Specific Engine
Cranks Excessively Questions and Answers
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