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Discussion Starter · #1 ·
Hey guys, I've got an incredibly confusing issue here and I've run out of ideas. Once every 5-7 times I try to start my firebird, I get a no crank no start with the only response being the starter motor gear engaging and retracting with a loud "clack". Here's the video:


This only happens every once and a while, and a couple of times that it has it would randomly decide to start after waiting for a few moments with the key out of the ignition. The battery is brand new and tested at over 12.75 volts the few times this has happened when I am at home, the old one had bad cells. I also just replaced the starter motor with a brand new one because the old one had a bad solenoid. The thing that is absolutely baffling me is the randomness and inconsistency with which it happens. I know it is not a mechanical fault with the engine, as when it does start, it starts and runs like a champ. Here's a video of it firing up the day I finished installing the new starter motor, which was only about a week ago. Only difference being is that it starts a little slower now because it was hooked up to a charger at the time:


I suspected that the alternator wasn't charging the battery but it appeared to be kicking out plenty of voltage, but I ordered a new one anyway because mine makes some strange noise and gets way too hot. Other notes to add, it seems to always start after being jumped with another running car, but seeing as doing nothing to the car and waiting a few moments has also resulted in the car going from not starting to starting, that could just be a coincidence. I also have one more video, this is of a voltmeter hooked up to my battery while trying to start the car:


Any help is appreciated and I can perform additional tests and answer any questions, thanks!
 

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On your 3rd vid, if starter was cranking engine voltage would drop way down. Your solenoid is clicking, indicating that voltage is reaching starter on small purple solenoid wire. But starter in not drawing power from battery to crank engine.

I would check the big positive battery cable that runs from battery to starter. Also check the large negative battery cable that runs from battery to engine block..

Disconnect each one at battery end. Check for continuity and 0 ohms resistance. Since problem is intermittent, wiggle each cable while checking to see if ohms reading changes. Also make sure end of negative cable is securely connected to engine block.

Because solenoid is working, we can eliminate ignition switch, solenoid, security, tdr (theft deterrent relay), and transmission position switch as suspects.
 

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Discussion Starter · #4 ·
Sorry it took me so long. My dad and I did some thorough investigation, and it would appear that the reason my starter motor isn't spinning is because the starter motor gear isn't meshing with the flywheel. Its just smacking into it and stopping before it can slide into the flywheel teeth at all. I haven't the slightest clue why this could be happening. The manual on the starter motor said no shimming was required. I took a slow motion video of the car starting, and from what I can tell it doesn't look like the starter motor is fully engaging even when the car does start, its only partially meshing with the flywheel teeth. Here's the video, you'll want to mute it by the way the audio is terrible:


This starter is brand new, is it possible that its faulty? I'm at a loss at this point.
 

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When the new starter was installed, did you verify the clearance between the ring gear tooth crown and the starter gear root? Should be 0.020".

This is an LT1, but the concept is the same.

http://shbox.com/1/starter_gear.jpg

Have you verfied good contacts/minimum resistance on all the wires, as seadog recommended?
 

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Discussion Starter · #6 ·
I have no way of accurately verifying the clearance between the ring gear and the starter motor gear, but I bought some shims and played around with them until I couldn't get it to misbehave just sitting in my driveway. I thought I had finally fixed it, but nope, drove to bubble tea and it did it in the parking lot when I went to leave. The manual for the starter motor said no shimming required, which i think might have been a lie, the shimming seems to have reduced the frequency with which the problem occurs, but its still there. I've checked my engine ground and the power delivery wire from the battery straight to the starter motor and both seem fine to me (my multimeter broke so I cant test resistance). My suspicion at this point is that the solenoid itself either isn't getting enough power or is too weak, is that possible?
 

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You might have a problem with the starter drive or the solenoid itself. Remember that either a new starter or a rebuilt one is no guarantee of getting good parts.

Here's how the thing works, when you turn key to start battery voltage goes to starter solenoid on purple wire. Solenoid energizes and starter drive slides out to meet ring gear on flywheel or flexplate.

When starter drive slides out to max distance, it closes the contact for the starter motor so battery voltage passes from large starter cable from positive battery post, to motor itself. Then starter motor cranks engine.

If starter drive does not move out far enough, contact does not close and motor does not run.

Or if contact in solenoid is defective, you can get intermittent starter failure .
 

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1993 6-spd T/A - 1996 C4
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On a brand new starter no shims are required. On a refurbished (reman) starter, shims may be required. Did you notice there was no ground wire on the starter? It grounds via the bell housing. When it is refurbished, they might mill a little bit of the mounting surface to clean it up. A reman starter that has made a couple rounds may indeed need shims.

My last starter actually included 6 shims and it needed every last one of them. I had to return it because it was very weak under load. Bench test passed, but, on the car, it turned over real slow.

The manual is correct, no shims are necessary. ...as long as the starter is actually new. Used starters may or may not need shimmed.

Good luck!
 

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Discussion Starter · #9 ·
I guess I will take the shims out then, but sea dog correct me if I'm wrong, isn't there suppose to be a meshing spring that allows the contacts for the starter motor to close even if the the pinion teeth hit the ring gear teeth and stop? That way when the motor begins to turn the pressure from the spring drop the pinion gear into the flexplate teeth? That's what led me believe that my solenoid is weak, or is not getting enough power. So perhaps it is not compressing that spring and is just stopping. What do you think? I think the contact in the solenoid is defective. I'll see if I can have it replaced on warranty.
 

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Did you look at the nose of the starter to see if you could measure the clearance between the ring gear and the pinion? 0.020" can be simulated with a standard paper clip wire. You can bend the wire into an "L" shape to insert between gear teeth. It is hard to get the starter gear out, hold it there and check the clearance, but it should be done when there is an engagement problem. While the factory manual indicates that the vehicle was designed for starter mounting without shims, it does indicate that shims, either double or single, should be used to correct a noise or engagement condition. My CVR Protorque starter required shims and several were included with the starter, Fortunately, that starter has no nose cone, and it was very easy to check the gear clearance and set it correctly.
 
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