2002 Cavlier won't start on gas

[curtises]

My 2002 Cavalier went in for tank inspection and passed, the next time it ran out of CNG it wouldn't start on gas.

The mechanic changed the fuel pump and, $1000 later, it didn't fix the problem.

Mechanic is now stating that it was one of the computer components - is charging $2000 to pull the computer from another 2002 cavalier and put into ours.

Didn't see any check engine lights when I was trying to get it to start.

Runs fine on CNG.

First... do you think it is the computer that is causing the problem?

Second... does the repair seem reasonable for the symptom?

Third... does the cost for the used computer seem reasonable?

[freedml]

Re: 2002 Cavlier won't start on gas

I think you need a new mechanic. Maybe take it to a Chevy dealer.

[siai47]

Re: 2002 Cavlier won't start on gas

I would agree, get a new mechanic---$2000 to pull and install a used computer from an existing car ?---A dealer could do that with a brand new one for that kind of money. I'll sell you a brand new computer for less then that and even tell you where the one bolt you have to remove to install it is located. Install a new fuel pump? The fuel pump isn't even used on the CNG side of the system. If the fuel pump, tank and lines fell off the car it wouldn't even slow you down if it was running on CNG. Seriously, take the car to a dealer and let him scan the ECU with a Tech2 and tell you what is needed. There are a lot of other things to look at and I can tell you where to look except it is 1:30 in the morning--I will get back to you on this. Meanwhile stay a long way away from this "mechanic"

[siai47]

Re: 2002 Cavlier won't start on gas

OK, I am awake now--I was traveling and haven't been on the forum for a couple of days. First let us look at the basics on your Cavalier. If the car was running fine on CNG after the tank inspection, and then failed to restart on CNG after running out and refilling with fuel, I don't think the tank inspection had anything to do with it. If the car then ran on gasoline, and you didn't have to tow it to your "mechanic", then the fuel pump (which only is used for gasoline operation) wasn't bad. The extreme cost of $1000 to change something that didn't need changing in the first place warrants a visit to your lawyer. The $2000 estimate to swap the AF ECU with one from another car is also extreme. You are being taken to the cleaners by this guy (note: this is just my opinion) I would get some distance from this guy and you might want to let others on this forum know who he is so others don't end up supporting him.

As to your car. The first thing to do is put the key in the ignition and turn it to the "run" postion. When you do, look at the little red light on the fuel switch on the dash. This is the FIL (fuel indicator lamp) and lets you know which fuel the car is running on. When you turn on the ignition, the lamp will light for a couple of seconds for a bulb check and then go out. At the same time you should hear a click sound from the trunk of the car as the High pressure lockoff valve is opened for a second to prime the system with CNG. If the lamp doesn't light, and you don't hear the click sound, then the AF ECU is not getting power or has failed. First thing to check is a 20 amp fuse located next to the battery. It is marked "CNG"--pull it out and check it to be sure it isn't blown. Also check the larger 40 amp maxi fuse marked "fan" or "cooling fan" to make sure it is also OK. (the fan circuit powers the 20 amp CNG fuse so if either is blown the CNG system won't operate). Report back on what you found .

[siai47]

Re: 2002 Cavlier won't start on gas

I give up---I must still be asleep. When I read your post again I finally found the word "gas" refers to gasoline and not NG. Yes, I take it back, the fuel pump could cause the car not to run on gasoline. In any event, the mechanic should be responsible for the $1000 charge for changing something that didn't solve or contribute to the problem. As to the AF ECU (computer), if the car is out of cng, it will automatically switch to gasoline---nothing in the CNG system is involved. Remove the 20 amp cng fuse and it will force a start on gasoline. Without power to the AF ECU the car doesn't even know it is a CNG vehicle and operates only as a gasoline vehicle. If the car won't start--I would look at the fuel pump relay which is located behind the drivers headlamp. This relay switches the gasoline fuel pump off when CNG operation is requested. When there is no power applied to the relay, it switches back to gasoline operation. If it fails to return to the gasoline position, the gasoline fuel pump will not operate. A dealer with a scan tool could find this problem in a couple of minutes. Unless there is a wiring problem, this is most likely where your problem is located.