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Jim Grant's Tech Tips
‘95 Nissan Altima, Without Warning
Q:
I was driving my ‘95 Nissan Altima to a friends house. Without warning the motor died. It is getting fuel at the fuel filter, and I tried to by-pass it with no result. The car will idle at 600 RPM, but it is not the normal idle and dies as I attempt to give it gas. Since I have owned the car the check engine light has been on but now it is not. I don’t understand that. I would appreciate anything you have on this as I am very, not wealthy.
- David
A:
It is a common misperception that engine-running problems will have a check engine light to go along with them. Alternatively, a check engine light means that there is an engine running problem. There are many causes that can turn on a check engine light that is not engine related and there are many engine running problems that will not turn on the check engine light. In your case it would be best to step back and forget about the engine computer and look at the basics first. More than 90% of the time, engine running problems are not computer related. There are basically 3 things needed for a sound engine to run. These items are fuel, air and spark. If any one of these items are missing the engine will not run. If one of the items is less than they should be the engine may run, but will not run well. That is just about what your problem seems to be. By-passing the fuel filter is not a good idea. All it takes is a small amount of dirt to get by and you’ll be looking at fuel injector problems along with your running problem. Just because you have fuel present at the filter doesn’t mean you have enough when the fuel system pressure is suppose to be operating in the 35 to 45 psi range. To correctly check and confirm fuel pressure requires the installation of a fuel pressure gauge into the system. You cannot just stick a pressure gauge on the end of the fuel line. Doing that is called a dead head pressure test. An electric fuel pump in a vehicle like yours can easily jump to 80 psi during this test and if done incorrectly can damage the pump. The money it would cost to go out and buy a fuel pressure gauge set that could correctly test your vehicle fuel pressure system is not really worth investing in. You’d be money ahead of the game to pay a repair facility to perform that test. Because the engine runs don’t rule out spark. A weak ignition can allow enough spark to the plugs to run the engine but not enough to ignite the air & fuel when you want to get moving. Inspection of the basics can be performed if you have a good understanding and the right tools. Be sure to realize your limits and don’t start bolting parts on or by-passing things like fuel filters. You may get more for your money by paying a qualified technician to diagnose the problem and then perform the repairs yourself, once you have the right information.
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