Troubleshooting The Starting SystemSix Corvette Starter TestsBackyard starting system diagnosis is pretty simple. Very few special tools are required, and for the most part, diagnosis can be handled in less than an hour. What follows could be old news to many seasoned Corvette enthusiasts. If you're stuck and can't trace a balky starting system, you might try the following:
Test One: Before you even consider a starter problem, you have to test the battery. A battery that's a dead player (or weak) can not only create starting troubles, it can make testing next to impossible. Once the battery is eliminated as the culprit, try this old mechanic's trick: Turn the headlights on and try starting the engine. If the lights go out when the starter is switched "on" and the starter doesn't spin, look for a poor connection between the battery and the starter motor. The number one cause of grief is a corroded battery terminal. The next biggest problem spot is a bad ground--especially where the ground strap attaches to either the car chassis (body) or the engine. In many cases, the problem is actually paint between the ground strap and the ground.
Test Two: If the lights dim when the starter is turned "on", and the starter turns slowly or the cranking action is sluggish, then the starter is experiencing a very heavy load. The number one reason for this in modified engines is too much initial ignition advance. If the engine has too much initial advance (or if it has mechanical advance weights and they're stuck) to start correctly, it tries to run backwards. The first thing to check is the mechanical advance. If it's stuck, free it. If the engine has too much initial advance dialed into it, reduce it. What if you need a bunch of initial advance to make your Corvette work (for example, a high compression Corvette race car with an automatic transmission)? Try separating the ignition and starting circuits. In other words, set up the wiring so that one switch (such as the key) turns the starter motor "on" while another turns the ignition "on." This way, you can get the engine turning quickly with the starter, and then flick on the ignition. It works.
Test Three: If the headlights on your Corvette remain bright when you turn them on, but the starter does nothing, then there's an open circuit somewhere in the starting system. The first thing to do is to hook up a booster cable from the battery + post directly to the terminal on the starter. If the starter still doesn't spin over, then it needs work. Another component to check is the neutral safety switch. If you by-pass the switch, and the starter functions, you've found the problem.
Test Four: If the solenoid (or relay) makes clicking sounds when you flick on the switch, but it starts with a direct shot of battery power (you can by-pass the solenoid by inserting a large screwdriver between the large battery cable post and one of the small switch terminals on the starter), it doesn't necessarily mean that the solenoid is healthy. Quite often, the contacts inside a solenoid can be burned. This makes it impossible for the solenoid to switch on the heavy current to the starter. The most effective fix is to simply replace the solenoid. If you've done that, and the starter still refuses to spin, it's time to tear it down for a rebuild.
Test Five: If the starter works periodically, but with obvious grinding noises, remove it and carefully inspect the armature shaft where it engages the starter drive. Believe it or not, this problem is very perplexing since the starter will work fine (even off the bench) for a number of "starts", but then it will refuse to function. You might be astonished to find a fractured armature shaft (this is an extremely frustrating problem that plagued a low mileage truck this writer once owned). Usually, the cause is poor engagement with the ring gear.
Test Six: Finally (and we're leaving the worst for the last), if the engine refuses to turn over, even if the starter is making a bunch of noise, you could have "hydrauliced" the engine. Since liquids (coolant, oil or gasoline) cannot be compressed, they don't allow the pistons (one or more) to go through their complete stroke. The cause could be a leaking head gasket, a stuck float or even a broken block. Remove all of the spark plugs and try spinning the engine over. If it turns over freely, you'll soon be met by one (or more) of the above fluids. That should tell you what the problem area really is.