Mazda mx5 will not start, turns over but will not fire, have changed air flow sensor & camshaft sensor, electrician has used a diagnostic machine but no faults showing, he is leaning towards an...
I'd probably trying back-testing through the ignition circuit to see if you're getting power to your spark plugs, then the leads and so on...
Here's a quick check I use to cover the most common starting problems - however a faulty immobiliser is definitely a possibly (which isn't covered by this quick list)
1. Check your battery voltage with a multimeter - you should have 12.5V or so across the terminals - any less than about 11.8 and you should think about a new battery.
2. Check that you're getting power from the ignition switch to the solenoid. The light-dimming check should help you out on this one, however, we'll make doubly sure. Locate your starter motor and the solenoid (the solenoid will be wired to the starter motor - the circuit is basically battery, ignition key switch (and immobiliser in this case), solenoid and starter motor). Disconnect the ignition cable from the solenoid (this is the heavier cable) and put a multimeter from it to ground (somewhere metal on the chassis). Get someone to turn the key to ON and check for 12V at the ignition cable. (Always put the car in neutral and the parking brake on etc...). If you don't get 12V here you've got a connectivity problem and need to trace your wiring back to your ignition switch and from there to the battery and try to find a poor connection or potential short - from the clicking sound this problem seems unlikely.
3. Now we want to test the starter motor to ensure it's OK. To do this, we need a large screwdriver with an nicely insulated handle. On the SOLENOID, you'll find to large electrical post connectors. Short across these with the screwdriver - be careful to only touch the handle or you're going to think someone has just kicked you in the groin...You should get some serious sparks and hear your starter motor whirring (don't let it run too long or you'll flatten your battery and possibly damage the starter motor). If your starter motor makes any nasty grinding kinds of noises, you need to replace or rebuild it. If it doesn't move, you need to replace it (or get it rebuilt). Sometimes you can 'rock' the car in gear to persuade the starter motor to move slightly and it will then turn for you.
4. If none of the other problem have suggested a component at fault, you probably have a faulty or 'sticky' solenoid. To check this, find which of the two heavy post connectors is connected to the starter motor. Place one probe of the multimeter in this wire and ground the other (metal on the chassis). Have someone turn the key (neutral and parking brake) and check the voltage. You should read 12V and hear a 'clunk' from the solenoid (this is the solenoid activating and sending power to the starter motor). If you're getting a low voltage and not hearing a clunk your solenoid is probably on it's way out and needs to be replaced. A quick fix that often works is to have your helper try to start the car and give the solenoid a bit of a tap with a rubber mallet. This might jar the mechanism loose and give the electromagnet a chance to pull it into the connecting position and power your starter motor.
Having a bit of a look through these things might point out a different problem in your ignition circuit - however the immobiliser is definitely a possibility and a place to start.
Hope this helps,
Jan 13, 2010 |
2001 Mazda MX-5 Miata