Sometimes the car won't start in the Morning

I purchased this car in April of 2012 for my 18 year old to drive. This car used to belong to the City of Phoenix and was used as a meter car for city employees. When the city used the car, the car ran on propane. Before I purchased it, it was converted to gasoline. Sometimes the car won't start in the morning. This problem started the first week we owned it. I figured there was a clog in the fuel injection system related to the car being converted to gasoline from propane. At that time, we did not take it in to the shop for repair, the problem seemed to work itself out.

During the summer months, the car would not start a couple times, but within ten minutes of the first try, the car would start up fine. Now that it has gotten colder, the car does not get through the week without having a morning where it won't start. At this point the little frustration it caused before has now become a bigger frustration because the problem is happening more often. In November we took it to a mechanic, he hooked it up to his computer diagnostics and no problems were found. The car always started up for the mechanic. Yet, the problem continues to persist.

So, this week we decided to take the car to a different mechanic for a second opinion. We let the mechanic keep the car for 4 days. Every morning, the car would start for the mechanic. They pressurized the fuel line and found no problems. The computer diagnostics found no problems. Finally, on Friday, a signal light came on the dash indicating there was something wrong with the anti theft device. So, the mechanics looked further into it and discovered that there was a problem with the device. So it was concluded that this device was not allowing the car to start, as a theft prevention. I asked the mechanics if they could dismantle the device or remove the device and they said it could not be done. It was a standard feature on the car and because of federal regulations, could only replace the device. We chose to replace the device. We were happy that a problem was found. I think the mechanic called it a sub deterrant anti theft device. In the process of replacing the device the car had to be re-keyed for the ignition. This was an expensive fix. We were glad to finally have an answer to our problem. We picked up the car last night from the mechanic.

This morning my child got in the car to go to work, and the car would not start. We are so frustrated. Now, we have paid all this money, fixed something that probably didn't need to be fixed and the problem still persists. The car just won't start.

The car has power, so we know it's not the battery. The car does not make a clicking noise at start up, so we know it's not the starter. The car attempts to turn over, but just will not turn over to start.

Before taking the car in to the mechanic this last week, we had been putting a large heavy blanket on the hood, thinking that the cold weather has been the problem. The blanket seemed to make a difference, but there were still days the car would not start even with the blanket on it. So we are not sure if the cold weather is the problem.

I think the problem may be with the fuel injection system. Why won't the problem show up on computer diagnostics? Or could the problem be related to the fact that the car used to run on propane?

Do you have any ideas or thoughts about what the problem might be?

Thank you,

Mrs. T