Auto Blogs | Car Forums

I OWN A 1997 BMW 540I, THE ENGINE WILL NOT TURN OVER.  BATTERY AND STARTER ARE GOOD.  COULD THIS BE AN IGNITION SWITCH OR RELAY PROBLEM?  IF, SO HOW DO I TEST THEM?  THANK YOU.

It can be any of a lot of things.
Check the battery terminal if it is loose or corroded, tighten and/or clean as needed.
See if you can turn the engine manually with a socket or open wrench using the crankshaft pulley bolt (key off or removed and on park). The engine may be stuck for a variety of reasons.
Check also if the solenoid gets power when you turn the key to start. If it does not, then it is a problem for mechanics and not do it yourselfers.
You may also jump the solenoid with battery power to see if it will crank the engine.
The anti-theft system (EWS) may not be giving the signal to allow the engine computer (DME) to start the engine.
The ignition switch (electronic part) or key cylinder (mechanical turning part) may be defective. Or the ring coil in the key hole bad.
The DME relay may be bad (open the E-Box, it is clearly identified). Replace same,  for testing it does not give a clear diagnosis as it may
switch but not provide enough amperage).
There is no magic wand that can tell you instantly what is wrong. You have to eliminate the possibilities one by one.