My 2002 Buick Century sometimes will turn over and not start. Problem since fall 2009. Replaced fuel pump. Scan reveals no problem. Cannot diagnose problem unless it happens there. Towed it Monday, car started at dealer. This happens about ever 3 -4 weeks, and usually starts in few minutes. Could this be an ignition problem?
I know this is an annoying problem but when it happens again the first thing needed to be done is to check to see if you have spark at the spark plugs. You can buy a spark checking tool at many auto parts stores. It installs at the spark plug and the spark plug wire plugs into the test tool. Have someone crank the car over and you see if the tool is flashing, if it is flashing then the ignition system is ok and you need to check for a fuel problem.
When the car doesn't start a fuel pressure test will verify if fuel pressure is available. Sometimes the fuel rail will not hold pressure, the system will leak down. When it doesn't start, turn the key on and wait two seconds, turn the ignition off, wait ten seconds and turn the ignition on again on for two seconds, then start the car. The reason for this is when you turn the key on there is a two second fuel pump prime; this builds up the fuel pressure before starting. If the fuel rail bleeds down the two second prime will not supply enough fuel pressure in the fuel rail to start the car. You will continue to crank the engine till fuel pressure builds up; then it will start and run fine.
Another possible problem is if you have the pass key ignition system, sometimes the key cannot be read and it thinks you are trying to start the car with an unauthorized key. Once this happens you will have to wait for three minutes before the system will read the key again. One problem it could be is the ignition key switch, sometimes it can't read the resistance in the key, and then you have to wait three minutes to start again.
It is hard to diagnosis but can be fixed if the technician can see the problem.
Hope all this information helps.
An intermittent no-start condition is never easy for you or the technician involved -- especially when it occurs days or weeks apart.
You either duplicate the condition long enough to diagnose, or replace parts with an educated guess.
The fuel pump itself has already been eliminated, but it still may not be working when it should due to a circuit fault.
The three important things to check while the engine is cranking -- but not starting -- is fuel pressure, spark, and injector pulse (on & off electrical signal).
No spark or injector pulse may indicate a lost crankshaft position senor signal (RPM signal to the control module). Spark, but no injector pulse can indicate a bad control module.
The technician may be able to provide you with a mobile scan tool which can take a snapshot of computer data when the problem occurs. This can be helpful, and if nothing else it gives you better odds on the educated guess.
Also, be sure they've taken a look at GM Technical Service Bulletin No.: 00-06-04-049B. This involves inspection/repair of a wiring harness which may have rubbed through on the A/C accumulator. This could cause an intermittent no-start.