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Jeep Grand Cherokee Won't Start

Q. Hi Vincent, First I want to thank you in advance for providing your professional advice on our problem. We have a 1995 Jeep Grand Laredo with a 6 cylinder engine that has 120,000 miles, mostly highway driving. It has an automatic transmission, fuel injection, no ABS brakes, has A/C, and cruise control.

Jeep Grand Cherokee Won't Start

The Jeep does not start right away under certain conditions. The problem occurred twice during the last two chilly and rainy days we had during the last two weeks. The engine turns but doesn't start. On both occasions we turned off both the manufacturers alarm system, which we never use, and the aftermarket car alarm.

After about 20 minutes of waiting and trying to start, it does finally start. We took it to one mechanic about two months before the problem started and they checked it over and gave it an oil change. We drove it back after the first time and they didn't find anything wrong. They are not great technicians but they are honest.

After the second time it occurred we drove it to a top notch mechanic shop I trust but it is far away. After a couple of hours of diagnosis there was a $995.00 estimate to replace the fuel pump, relay and fuel filter, with the diagnostic charge and labor. The fuel filter was pricey because they wanted to install an OEM pump with a lifetime warranty. They do good work but they are $$$, and they do cut back on the estimate once the job is completed.

The shop explained that they checked the fuse, several other things and ran power directly to the fuel pump and didn't get fuel pressure. So we decided to wait and think it over. I was very concerned that if this did not solve the problem, the next step is to possibly replace the control module. By the way, we paid the diagnostic charge and the car started right up and ran fine. It was 65° and sunny then.

My question is why does the car run great once it starts? What else could be keeping the car from starting properly under these conditions? Or is it really the fuel pump? Some more notes; the car is kept up mechanically and we buy name brand gas such as Mobil.

I am auto mechanically inclined, so with guidance I can check most anything that does not require a mechanic's computer. Have to get one of those someday. That's all I can think of, so we look forward to hearing your opinion.

Joe and Grace

A. What is lost when it won't start? Fuel or spark? This is the first question you must answer before you start troubleshooting the problem.

To be honest, when I see a problem like this on a car with an aftermarket alarm system, I tell the customer to take it to the people who installed the alarm. About 75% of the time it is the fault of the aftermarket alarm. I'm not trying to get out of the work, it just saves the customer from spending lots of dollars to diagnose the problem and usually wind up telling them it is the fault of the aftermarket alarm.

When this happens we have to determine what is lost when it won't start, fuel or spark. The next time it happens, take a hose off the intake manifold and shoot some carburetor cleaner inside it. Try to start it and if it starts right up, you have a fuel problem. If it doesn't, take off a plug wire and stick an old spark plug on it. Lay it on something metal so you have a ground and crank it. There should be a nice, bright blue spark. If not, you have an ignition problem.

© 2003 Vincent T. Ciulla

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