tbag_skywalker

Doing this resistance test won't necessarily tell you if the cables are bad. The voltage a multimeter uses to check resistance and continuity is extremely low and therefore will show low resistance in this case, but that doesn't mean the resistance is actually low enough to give the starter enough juice to start the engine.

Something is causing voltage drop, something is putting a load on your battery besides the starter motor when you try to start the car. Next thing I would do would be start replacing cables, starting with the least expensive.

Paul Bell

iTrader: (9)

Guys, the fact that his voltage during cranking drops as much as it does indicates his cables and connections are good. Cable/connection resistance is NOT the problem here.

It looks to me (and others) that the starter is too close to the flywheel/flexplate.

OP, have you shimmed the starter out yet?

tbag_skywalker

I'm not disagreeing with you, I know you know a lot more than I do about LT1's and engine building. And I wouldn't be surprised at all if you're right about the starter shim.

But I can tell you that if a cable is in bad condition, but still conducts electricity, even though a fluke meter shows low resistance it will absolutely cause excess voltage drop under heavy load.

Paul Bell

iTrader: (9)

Voltage drop is the result of a heavy load (current being drawn). If there was a poor or high resistance connection or cable in the path between the battery and starter motor, current draw would be low and the voltage drop would be minimal.

The starter motor is drawing a lot of amps. This shows the battery and all the connections are good.

Take a handheld drill. Run it free. It doesn't draw that much power (current). Now grap it's chuck and try to slow it down. Now it'll draw more current through it's power cord.

Ohm's law at work.

jaycenk

iTrader: (1)

Not true. If you under stand that it should have no resitstance and you have any resistance it is a problem. It does not mean that the cable alone is the smoking gun. He also said he had a good starter and it did the same thing in this car. Either a bad pinion to fly wheel gap as mentioned, bad battery or not enough current getting to the starter.

jaycenk

iTrader: (1)

No true either. resistance with amp draw will cause amp burn off. in the form of heat and still cause a power draw since resistance is basically a controled short. Not to mention he tested the power at the cable connection at the battery and not the batery terminal it's self. If the resistance lies in the connection at the battery terminal you will only show 8 volts when testing it on the other side of the resistance point.

Paul Bell

iTrader: (9)

Look at it this way guys: The power (current) is going somewhere. IF there was a high resistance point somewhere in the electrical path, the current would (A) be lower (resulting in less voltage drop) and (b) show itself as a burning/hot cable or connection point burning/arcing.
　
The OP already said he’s checked his cables and connections and they’re good.
　
The higher the resistance a circuit is, the less current it will draw. Bad/poor connections would cause higher resistance and the battery’s voltage would not be drawn that low.
　
The OP’s starter is drawing so much current that’s it’s pulling the battery’s voltage lower than normal. Where is all this current going? Into the starter motor as it’s struggling to turn the engine over. If somehow all this current would magically be getting absorbed by the cables or connections, there would be clear signs of it.
　
This really is very simple guys. The starter needs to be shimmed away a bit. It’s not an electrical issue.
　
Time for za355tx to step back in here and let us know where he is with troubleshooting this.

tbag_skywalker

jaycenk, I understand what youre trying to say and it makes perfect sense, but we need a little more information from OP in order to determine if he's got problems with bad cables/electrical connections or if its just that the starter is shimmed too close to the flywheel.

za355tx, this is what i think you should do as your next step in trouble shooting.

If you've got any way to measure your current flow while trying to start the car that would help a ton. If you're getting excess current flow, than most likely Paul's idea that your starter is shimmed too close to your flywheel, causing your starter motor to work too hard is true.

If your cranking amps are normal, but youre still getting excess voltage drop, than you've definately got a bad cable, or maybe a bad contactor on your starter relay, basically something electrical.

I say this because if a wire is damaged, (for example if a decent chunk is somehow accidently taken out of your starter motor wires), if you try to measure resistance through it, the resistance will likely still be very low, just as low as it was before it was damaged. However, now when this said wire is trying to carry a big load, you'll see excess voltage drop without an increase or decrease of normal current flow.

This is something a bit more complicated than ohm's low, and jaycenk, I wish you would try to wrap your head around this before telling me that my information is incorrect, because I know that it's not. Go ahead and disagree with my theory on what's causing the problem, but do not tell me that my information to back it up is incorrect. I do electrical work for a living, this is nothing new to me.

za355tx

iTrader: (108)

I actually have already replaced the 12v wire to the starter with a big a$$ cable and no change.

I'm not thinking it has anything to do with the spacing or shims because the problem actually happened before the starter went bad. Basically we replaced the starter but it has the exact same symptoms as before. All the sudden one day it started spinning slow and did not start...so we replaced the starter thinking it was the issue and the car did the same thing. So that leads me to believe that whatever the problem is...happened before I put a new starter on. I've never had to shim a starter though or have one too close to the flexplate but why would that cause a power drop?

So the wires can be bad even if we tested resistance and everything checked out? Should I just replace all the wires? Ground and all?

Paul Bell

iTrader: (9)

This is a tough one. Although it's probably not the battery or cables, replacing all the cables to new ones will positively eliminate them as the cause of the problem.
　
I’m thinking the issue is mechanical. Are the starter bolts all good? Any chance that the starter is twisting while cranking?
　
Can you turn the engine by hand with a breaker bar on the balancer bolt?
　
Does this engine start at all? Have you tried shimming the starter yet?

jaycenk

iTrader: (1)

is it an auto or a stick?

za355tx

iTrader: (108)

It's auto and no I have not shimmed the starter. The bolts seem good. I may try to replace the cables, we have plenty of good ones. Still a little lost though. It went from starting perfectly to not at all.

Paul Bell

iTrader: (9)

We're all a little lost on this one. I've been thinking about this, I'm hoping you do the "can you turn the engine by hand with a breaker bar" test next.

za355tx

iTrader: (108)

I will but my initial thought is that it's ok and not partially locked. But that will be the next thing I do.

tbag_skywalker

This was gonna be my next suggestion, after that I'm pretty much out of ideas.

Can't remember if our motors even have one, but have you tried swapping in a new starter relay? Never had to look for it on the LT1, but I know there's cars out there that don't have starter relays at all.

Hopefully there's nothing wrong with your motor.

Charles Huffmon

Hey I am having the exact same problem. Did you ever figure out what was wrong? Thank you

QwkTrip

iTrader: (23)

When I read the OP's posts it leads me to think that the contact patch between starter and engine block was rusted/dirty. It's the only part of the starting electrical circuit that he never describes checking or cleaning.

That type of starter doesn't have a dedicated ground cable, it grounds by physical contact to the block; And then the engine block has a ground wire to chassis or battery.

QwkTrip

iTrader: (23)

I had to read the thread to get context to help you, and oh, my gosh.... reading the argument about how things work was really painful. I can help clear up all that.

It's easiest to think of the system as three things:

1. Battery (the power supply)
2. Starter (user of power supply)
3. Losses. These are all the cables, connections, engine block, chassis, grounds, etc, etc that make up the electrical circuit between starter and battery. They all add up to some total resistance.

The starter only sees whatever voltage is across its own body. The lower the voltage across the starter the slower the cranking speed.

• If the battery is at 10V during the crank, then the maximum voltage the starter can see is 10V of course.
• If the B+ cable has a 2V loss, then the starter will see only 8V across itself. That's intuitive to most people.
• If the Ground side has a 2V loss, then the starter will see only 8V across itself. That's not so intuitive to some people.
• Combining those concepts, if the B+ and Ground each have 2V loss, then that's a total loss of 4V and the starter will see only 6V across itself.

Bottom line is resistance anywhere in the starting circuit causes voltage losses and slower cranking speed. If you want to measure how much voltage loss you have then what you do is crank the engine and measure voltage across the battery terminals, and voltage across the starter. The difference between those numbers is the losses in all your cables and connections. Try to keep it under 1V.

That's really all you need to know. You can stop reading here and be able to figure out what's going on. If you want to get a little deeper then read on....

The battery is the power supply to the starter motor. The way a battery behaves is the battery voltage goes down as the discharge current increases. In other words, the more current the starter draws the lower the measured voltage across the battery.

Now the really important thing to understand about the nature of the starter is that the current goes up when the starter spins slower, and the current goes down when the starter spins faster. It's the nature of the beast and I don't want to explain why.

• What makes a starter spin slower? (1) Lower voltage across the starter; or (2) turning against a bigger load (more torque).
• And what happens when a starter slows down? Motor current goes up.
• And what happens to battery voltage when current goes up? Battery voltage goes down.

Lastly, what most people don't realize is that low batteries can still provide a shitload of current. So when a starter cranks on a low battery the starter spins really slow, motor current goes sky high, and the "weak" battery dumps a huge amount of current into the starter and the starter burns. And if the solenoid chatters it will literally turn the copper contacts into a molten mess. Never ever crank on a low battery. Never.