Questions and Answers

Jeep Grand Cherokee Hard Start
Q. 1994 Jeep Grand Cherokee, 4.0 liter, automatic transmission and 135,000 miles. Two questions. Starting to experience hard starts and rough idle. Engine is tuned and in specification but hard start persists. Could this be a problem in the ignition system. How do I diagnose?

Second question, same vehicle. Power windows stopped working after intermittent problem. None of the switches is operative individually nor is the master. Replaced the 30 amp breaker with a verified good replacement, no change.

Is there a master module for the power distribution and control? If so where? Any diagnostic suggestions? I do not have a heated garage and have not been able to pull the door panel due to cold and wet winter weather.

Thanks,
Ted
Virginia

A. Here is a basic troubleshooting chart for hard starting.

SYMPTOM DESCRIPTION:
Engine cranks okay, but does not start immediately. Will eventually start and run, but may die shortly after.

Possible Cause	Action
Starting System Malfunction	Check Battery voltage. Check Alternator output voltage. Check Starter current draw.
Ignition System Malfunction	Scope check Ignition System. Check ignition coil for proper output voltage. Check spark plugs for proper spark duration. Remove spark plugs, check for fuel fouled plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Replace as necessary. Check secondary circuit for abnormal firing kv, crossfire between spark plugs (distributor cap, spark plug wires), and proper plug wire routing. Check ignition timing for excessive spark advance or retard.
Engine Mechanical Malfunction	Check COMPRESSION Perform a compression check, and cylinder leakage test, look for sticking or leaking valves. Check for VACUUM LEAKS inspect Intake manifold, gasket(s), and hoses. Check exhaust system for leaks, restriction, or damage.
Fuel System Malfunction	Check for lean Air-Fuel mixture, O2 Sensor, perform injector balance test, inspect regulator operation (check vacuum line and return hose), check fuel pressure. Check Fuel Pump for defective check valve. Check for defective Fuel Pump Ballast Bypass Relay.

As for the power windows, try this.

1. Measure voltage at 30 amp circuit breaker #26 at fuse block. Meter should read battery voltage. If not, replace or repair open to 60 amp fuse #13 in Power Distribution Center (PDC) as required.
2. Turn ignition switch to off and measure resistance from ground lug on left side kick panel to ground. Meter read zero ohms. If not, repair open to ground.
3. Remove master power window switch on left front door. Measure resistance at black wire (terminal one of green connector). Meter should read zero ohms. If not, repair open to ground.
4. Turn ignition switch to on and measure voltage at terminal 5 of black connector. Meter should read battery voltage. If not, repair open to circuit breaker #26 in fuse block.
5. Close master window switch. Measure voltage at terminal 1 of black connector. Meter should read battery voltage. If not, replace switch.
6. Operate window switch. All windows should operate.