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Troubleshooting / Cranks but Wont Start

Engine Cranks But Will Not Start

Troubleshooting Procedure

(Definition: the key is turned and the engine cranks, but does not start)

For an engine to run, you need three things to happen inside the engine. Compression, fuel and ignition, without any one of these components the engine will not run.



Compression: All internal combustion engines require compression to run. The most popular reason for an engine to lose compression is a timing belt or timing chain fails. Remove the spark plugs and perform a compression test. Most engine's normal compression reading is between 125 psi. and 160 psi. on each cylinder.

Fuel: All internal combustion engines require fuel pressure to operate. One of the most popular reasons for a fuel system to fail is the fuel pump. This cause's the fuel pressure to drop and engine to stall or not start at all. To check the fuel pump pressure, remove the fuel rail pressure inspection port and attach a fuel pressure gauge. Fuel pressure reading's vary depending on the system your in our vehicle, but most throttle body injection cars (TBI) are between 13 psi and 17 psi. and most (DPI) direct port inject systems are between 40 psi and 55 psi.

Spark: An electric spark is used to ignite the fuel air mixture in the combustion chamber. This spark is generated by the ignition system by the use of an ignition coil. Once the spark has been generated it is transferred to the spark plug for fuel ignition. Some of the most popular reasons for spark operation failure is ignition coil, ignition distributor, ignition module and crank angle sensor or spark plug.



Basic Checks:

A. Test Fuses. Test both under hood power distribution center and the fuse panel under dash. This is done with a test light tool. The test light should illuminate on both sides of the fuse, if not the fuse has failed and needs to be replaced.
 
B. 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. and most (DPI) direct port inject systems are between 40 psi and 55 psi. If no or little fuel pressure is observed and there is 12 volt power present the fuel pump, the fuel pump needs replacing.
 
C. Checking Timing Belt  Test for compression by removing a spark plug and insert a compression gauge. Crank the engine over about 5 seconds the gauge should read between 125 psi and 165 psi, if no compression is observed remove front engine cover to inspect timing belt or chain. Crank engine to observe cam rotation, if the cam does not rotate the timing belt or chain has failed. (note: if the timing belt drives the water pump it is best to replace the water pump at this time)
 
D. Test for Injector Pulse  Remove injector connector to insert injector test light (node) or volt meter. Observe light flash or gauge pulse while cranking. If light/voltmeter doesn't respond, an ignition distributor/crank angle sensor (CKS) or an ignition module is most likely your problem.
 
E. Test for Ignition Spark  Remove spark plug wire, insert an extra spark plug into end of wire, rest spark plug next to a ground source then crank engine. You should observe a blue spark between the spark plug gap and ground source. If no spark is observed, an ignition coil, ignition rotor or spark plug wires might have failed. (always keep hands away from engine when cranking)

Troubleshooting / Cranks but Wont Start

Check Manufacturer Specific Engine Wont Start Questions and Answers

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