You first have to go to basics. You need spark, fuel and compression. First thing to check is for spark at the spark plugs. If you don't have spark the most common Item in the vehicle to fail would be the crank sensor. But check the whole system to be sure it isn't something else like bad or poor wire connections or other failed parts related to the ignition system.
If the vehicle has a key fob try to lock the doors with it then open the vehicle by hitting the open button. sometimes the immobilizer in the security system can get disrupted and cause the motor to not start.
Check all fuses to make sure there are no blown. There are many fuses for different systems, if one is blown the engine may or won't start.
Check for fuel pressure and the amount of fuel coming out of the fuel line. The fuel pressure should be about 30 to 45 psi.
If you have spark and fuel pressure then check for compression of all cylinders. Compression should be in the range of 135 to 150 psi per cylinder.
Having a scan tool can help. If you know anyone with a scan tool; check for any trouble codes stored in the computer. This can be a big help.
I hope this information help you.
I have a 2000 Ford Expedition that kills the battery when I turn the ignition key. What could be the problem. Where should I start looking to solve this problem. I turn it on but not to start it to see if I can get a code but it won't recognize my OBD2 scanner. Or nothing is coming through my scanner. My scanner works I tried it on my other vehicles.
I don't understand what you mean that when you turn your key on it kills the battery.
Check your voltage at the battery, check your battery connections making sure they are clean of all corrosion. Take the battery out and have a automotive repair shop or parts store load test the battery to see if it is a good battery.
If the scanner does not communicate check your fuses that would be related to the PCM.
This is just a few suggestions, get back to me when you can with your results we can diagnosis the problem further if needed.