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Fuel, air, spark Posted by Ari [Email] (#2847) [Profile/Gallery] (more from Ari) on Thu, 15 Apr 2004 06:01:15 In Reply to: Saab 1997 900 starting problem, b smith, Tue, 13 Apr 2004 09:35:57 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The Holy Trinity of getting an engine to run.
Air is pretty easy, but it never hurts to make sure a squirrel hasn't nested in your air filter. Have someone push the accelerator pedal while you make sure the throttle plate moves. Pull the fat hose off the throttle body and make sure all seems clear. Of course, look for obvious things like hoses off.
Pull the fat hose off the intake plenum after trying to start the car, and sniff. Do you smell fuel? If you don't smell fuel, then start to suspect the fuel pump or fuel pump relay. However, you can't ignore the crank sensor - the fuel pump relay won't close if the system doesn't think the engine is turning, and it uses the crank sensor for that.
Spark - you've got a distributor system. Get a spare spark plug, and pull a wire off one plug. Stick the wire onto the spare plug, and ground the plug body to the chassis, while someone cranks the engine. Do you see a spark? (I don't like just holding the wire near some metal, because you can accidently ground it and damage the ignition system). When you crank the engine, do you see the tach needle bounce? If the needle isn't bouncing, then I would suspect the Hall Effect cam sensor (or associated wiring). If the tach needle does bounce but no spark, then check for bad wires, bad coil, or bad ignition amplifier. If you've got spark, go back to fuel.
These are all very general things - sorry, there usually isn't something as simple as "hit the hidden reset button." And there are a lot of things that can cause a car to be plain dead. But start at the engine and see if you have fuel and spark (and air). If you're missing one or another, start working backwards.
Good luck!
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