[garyberg]

I crank on it .it has full cranking just won't fire

[smoothy]

Any computer codes?

[TxGreaseMonkey]

Basic Ignition System Troubleshooting


Greater than 90% of all "crank but won't start situations" are electrical-related, not fuel. The tests below assume there is no problem with the timing belt or engine compression.

A summary of tests that should be followed, if you are experiencing a "crank but won't start situation," are:

1. Battery Test. Remove and fully charge the battery. Most auto parts stores will test and charge batteries for free. Clean the battery terminals and connections.

2. Fuse Test. Check all under hood and under dash fuses with a test light or multimeter. Using a test light or multimeter is faster, more accurate, and eliminates the possibility of replacing a fuse in the wrong slot. This is easy to do in the dark and cramped location of most under dash fuse boxes. Be very thorough, since it will save a lot of time and money. Determine everything that is on the circuit, for a fuse that blows.

3. Check Engine Light (CEL) Test. Turning the ignition switch to ON, does the CEL come on and then go off after 2 seconds? If not, a fuse may be bad; the PCM may be failing; the main PCM ground may need cleaning; or the ignition switch may be bad, due to wear, pitting, or melting.

4. Fuel Test. During the 2 second interval that the CEL is on, do you hear the fuel pump in the gas tank run? If not check the fuel pump fuse and fuel pump relay, in the under hood fuse/relay box. Remove and clean the contacts to the fuse and fuel pump relay. Consult your Owner's Manual for their locations. If you hear the fuel pump in the gas tank run, the odds are that the fuel pump is fine. Modern-day fuel pumps are extremely reliable and rarely ever need replacing. Many mechanics, who don't know what they are doing, rush to replace fuel pumps. $750 later, the customer finds out the fuel pump was fine and was not the problem after all. Instead, focus on understanding the electrical aspect of the fuel system, including the ECM. I've seen many cases where simply cleaning the main ECM ground solves the fuel problem.

5. Diagnostic Trouble Code (DTC) Test. Attach a code reader to the under dash data link connector, turn ignition switch to ON, and record any codes that were thrown.

6. Spark Test. Perform the standard spark test; i.e. remove a spark plug wire and attach it to a properly gapped spark plug, touch the plug to a convenient ground, and observe the spark, while someone cranks the engine. Look for a good, solid spark. If the plugs don't spark properly, a) replace the Ignition Control Module (ICM) and coil, or b) replace the Crankshaft Position Sensor (CKP) and coil on distributorless ignition systems (DIS). ICMs, especially, are very problematic. I recommend replacing ICMs, CKPs, and coils every 120,000 miles or 10 years, whichever comes first. Bench testing ICMs and coils are not reliable. Frequently, even if the plugs spark, the ICM is bad because heat has affected the microchip inside and it does not fire when the PCM wants it to. Crankshaft Position Sensors set ignition timing, supply the RPM signal, and determine engine speed.

SUMMARY

If the CEL comes on and goes off normally, all fuses are good, there are no codes, you have spark, the fuel pump runs, but the engine does not start, the ICM or Crankshaft Position Sensor (CKP) may be bad and should be replaced. CKPs, because of their proximity to the crankshaft and exposure to the elements (water, salt, grease, dirt, and stones), commonly fail. Exposed to high heat and vibration, the extremely thin coating of insulation on tightly wound CKP coil wire can break, causing an internal electrical short. Heat can, also, crack the sensor's housing and even cause the coil windings to expand, leading to failure.