Start with the basics, and work your way up, Last tune up was? Wires plugs ALL filters? If all that is ok, check for a stuck EGR, then test fuel pump pressure, If it won't restart, determine what's missing, the engine needs three things to run, Spark at all plugs, gas to all cylinders, and compression in all cylinders, tho an engine may run lacking one in one cylinder, it won't run very well!
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and this one!
If the check engine light is on, read the codes, the computer is trying to point you in the right direction.
Readers can be purchased by following the link in my signature file, this is a must do step for all computer controlled cars.
1. Ensure battery has a minimum of 12.5 volts (9.5 cranking volts) available to operate cranking system. Ensure battery cable connections are clean and tight. 2. Using an analog voltmeter, backprobe the following wires at the distributor. Touch positive lead to Tan/Yellow wire (Gray/Black wire Grand Cherokee). Touch negative lead to Black/Light Blue wire. 3. Set voltmeter to 15-volt DC scale. Crank engine. If voltmeter needle does not fluctuate between 0-5 volts, check related circuits. If necessary, replace camshaft position sensor. If camshaft position sensor is okay, but engine does not start, see G - 2.5L & 4.0L TESTS W/CODES article in the ENGINE PERFORMANCE Section and check PCM. NOTE: Perform SECONDARY SPARK under IGNITION CHECKS before proceeding with test.
SECONDARY SPARK Spark Test 1. Remove coil wire from distributor cap. Hold end of cable about 1/4" from ground. Crank engine. Spark should be present and constant. If spark is not present and constant, check coil and coil wire resistance. Perform IGNITION PRIMARY test under IGNITION CHECKS. 2. If coil wire spark is present, ensure spark reaches spark plugs. Check condition of rotor, cap, spark plug wires and spark plugs. Repair or replace if necessary. Spark Plug & Coil Wire Resistance Resistance should be 250-1000 ohms per inch. Use insulated pliers to avoid getting a nasty bite!
Friday, July 3rd, 2009 AT 4:45 PM