Ok so I hooked up the voltmeter and with no load the battery is in the high 12's. Below is a video while it is cranking. (The connections got loose towards the end, that's why it went to zero, but the battery was still at 12.7 after cranking)

 

If you have a amp clamp handy, I would bet that you would find your starter is bad and drawing crazy high amps. That's why the battery voltage goes so low.

 

As people have said. What I notice is your lights dimming while cranking. That is has certain points where it dims then comes around. Have you changed the starter yet?

You are turning the motor as we can see. Why isn't it starting? Usually all you need is for the motor to spin, get to a couple power strokes, & it should fire up. Have you checked the plugs? Are they firing? When was the last time you changed the opti? Maybe it went & it's firing at the wrong spot? Hope you get it figured man. Stay posted.

 

Well I just took my starter to Advance Auto to have it tested, but it was still good. They say it tests voltage and spin speed. I figured it was still good, but wanted to test it, unfortunately that doesn't help me figure out what's wrong.

I think I have some clips for my voltmeter, if I can find them I will measure the starter wile I crank it. The opti is not even a year old and probably only has 1000 miles on it. I just put in new plugs and gapped them while I had the motor out for a cam swap. I haven't checked them because my understanding is that even without spark or fuel the motor should still turnover continuously and not stop and start like mine.

 

Did they load test the starter? Voltage and spin speed don't mean crap without a load on it.

Don't even think of worrying about the opti until you figure out what is causing this slow crank problem.

What really puzzles me is why people go and make performance modifications on a car that was not running right from the start. Fix the current issues with the car, THEN start making mods when you know the thing is working okay. Otherwise, you end up with headaches like this....

I don't think putting a voltmeter on the starter is going to tell you anything(well, I shouldn't say that...it can tell you some things if you know what to look for...)....but if the problem is high resistance of the solenoid contacts you might be able to see a high voltage drop between the starter motor post and positive post on the solenoid. I'm assuming that the cables are good as you just replaced them.

Otherwise, you need a DC amp clamp to find out how much current is being pulled and what circuit is pulling the most load.

Edit: I just went out to my Z28, disabled the PCM, put my Fluke 85 on it and watched the battery voltage as I cranked it. There is an initial current spike that quickly drops the voltage to 9V, but then the voltage rises back to around 10.5 volts(as the engine gets spinning) and stays there during constant cranking.

So 10.5 volts is the goal you are looking for during constant cranking. This value could vary a little depending on the current delivery capacity of the battery.

As an FYI, battery voltage alone is not the end all and be all of battery health.

 

The battery voltage is dropping so low, I doubt the PCM is working properly during the cranking time. So the thing doesn't even stand a chance of starting.

 

You're right. What I wonder is how/why it seems to have the spikes of voltage loss through the crank. Not a constant draw.

 

Well from the battery standpoint, it boils down to this...

The battery can't meet the load demand being put on it. This formula can show you why.... and this is simplifying things some but I think it will show why the voltage drops.

Watts = Voltage x Current

Say you have a battery that is rated for 500A @12V.

Via the formula above, that shakes out to 6000 watts.

Say you put a load on the battery that pulls 600 amps....instead of 500 amps. The power that the battery can deliver is 6000 watts. That can't change, but if your load is trying to pull 600A the number that changes will be the voltage.

6000/600 = 10V.

So... in general, that is why voltage falls when you try to pull more than the rated current capacity of a power supply.

There are other factors to consider and I have over simplified the above, but the bottom line is there is simply too much load on the battery(bad starter, very high compression engine, something else other than engine load causing issues....there is transmission load to consider too) or there is a problem with the battery.

I would start troubleshooting this by putting a DC amp clamp on the positive cable running to the starter to see how much current it is pulling when starting. I'll try to get a reading off mine as a baseline in a day or so.

Something else to consider is to make sure that the grounds to the chassis and engine are in good shape. High resistance there could really cause problems during high current situations.

Have a look at this...for what a ground issue can do...from ScannerDanner's excellent youtube channel.

 

Well aBout two weeks ago my starter actually broke when I was trying to start the motor. The gear got stuck in the flywheel, I popped it out, but now it won't engage and spins freely. Anyways I bought a new one, the smaller corvette one, and it is cranking a little better. You can see in the video below there is clearly another problem with the car not running that I will start looking into, but does the voltage and cranking seem correct??

 

Has the car run since you did the cam swap or did the car show shades of this issue before the work? Have you scanned it for codes? The way the engine is cranking it seems like its way out of time or that something is creating a ****-ton of drag on the starter.

 

Have you tested your alternator? When it gets going for those few seconds you would think voltage would jump as the alternator takes over.

 

Speaking of alternators.. are you sure the voltage regulator connector plugged in? By the way it's behaving it would look like there is not enough power to keep the car running. As stated, seems the alternator is not doing it's job.

 

Having made this same stupid mistake on my car, I am pretty sure it will run with the alternator completely disconnected - provided there is enough juice in the battery to run the engine's vital electronics. Same thing would happen if you snapped the belt. I left the voltage regulator unplugged on my car by accident and it ran just fine. Now, that being said, the volts on the dash-gauge start at 12 or so, and then go way, way low, so I wonder what is the actual voltage at the battery and the alternator.

 

I would say the car showed issues of this before the cam swap. I think the battery was dying off and it would slow crank often, but would almost always catch and start up, then it ran fine. It has officially "started" twice since the cam swap, but both times it got it started I had to keep my foot on the gas, roughly 2000 RPMs and as soon as I let off it dies. I have cranked it many times where it does not start, just after installing the new starter did I have it start, run for a second, then shut off.

I had been regularly scanning for codes and none showed up until last night when i recorded the video. It was a P0100 code for MAF which make sense because it is unplugged right now.

I have not tested it yet, as I mentioned last night was the first time it would fire up then die, so i hadnt thought of it yet. I will look into it.

I am almost positive that it is plugged in, I remember doing it, but I will double check tonight.

 

It will run if there is enough power in the battery. His barely has enough power to turn the engine over much less fire the ignition. It would seem the alternator is not making a connection to the battery. Op posted a vid of voltage at the battery in this thread.

 

That right there is worth a second look. Why people keep using that operation is beyond me. Reach out to Moe Bailey and see what he can provide for you.

moehorsepower@peoplepc.com

One of the best tuners out there and cheaper than almost all of them, to boot.

 

I plugged my stock PCM back in and still have all the same issues, so I dont think the tune has much to do with it right now.

 

So after doing some quick searches, I am not exactly sure how to test the alternator. Most things I read talk about using a multimeter while the car is running . . . I wish the car was running!

 

Take it to a parts store and have it tested. After watching your voltage video it still seems like there's something else wrong, like there's a huge draw on the battery before any power gets to the starter. I dunno. I hate electronics.

 

Ok, I might as well try that just to be sure.

I 100% agree with you on that! It pisses me off that I have already done all the hard work of pulling the motor, doing the whole swap, and putting it back in only to have to tinker with electrical sh*t. I guess its a good learning experience though.