Voltage Drop Question - Team Camaro Tech
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post #1 of 12 (permalink) Old Feb 9th, 06, 03:50 PM Thread Starter
 
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Voltage Drop Question

Anybody out there know how to measure the voltage drop from a trunk mounted battery to the starter during cranking? Every now and then I get a hot start problem when it heat soaks. I have a good 900 amp battery and decent gear reduction mini starter so that cant be the problem.
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post #2 of 12 (permalink) Old Feb 9th, 06, 04:17 PM
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Re: Voltage Drop Question

Get your trusty voltmeter and hook one end to the battery positive terminal and the other end to the starter. To make things easy, use some primary wire as an extension so you can have your meter close at hand when you start the car. You might also check the voltage drop from the engine block to the battery negative terminal using the same type hookup. Another test is to measure the solenoid voltage when you start the car, measured from the solenoid connection to the block.
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post #3 of 12 (permalink) Old Feb 10th, 06, 12:53 AM
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Re: Voltage Drop Question

Quote:
Originally Posted by rlovell383
Every now and then I get a hot start problem when it heat soaks. I have a good 900 amp battery and decent gear reduction mini starter so that cant be the problem.
What kind of hot start problem? Do you just get a click from the solinoid, or does the starter turn slow. Post back.

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post #4 of 12 (permalink) Old Feb 10th, 06, 09:16 AM Thread Starter
 
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Re: Voltage Drop Question

I have a remote mounted starter solenoid so the engine always "wants" to crank just veeeery slow. It will hardly turn it over. Its strange its either all or nothing. If I jump it with cables it spins it over like nothing. I am currently relying on the frame as my ground wire to the front which I think is my problem. I ordered a Taylor 1 ga cable kit to string from the batt directly to the motor.

So if I put the volt meter positive on the battery where exactly do I put the negative on the starter? Thanks guys
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post #5 of 12 (permalink) Old Feb 10th, 06, 09:25 AM
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Re: Voltage Drop Question

If you want to measure the voltage drop across your battery cable you should put one meter lead on the battery+ and the other lead on the battery cable at the starter. If you want to include any drop across the solenoid switch, put the other lead on the motor terminal of the solenoid.
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post #6 of 12 (permalink) Old Feb 10th, 06, 04:33 PM
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Re: Voltage Drop Question

Quote:
Originally Posted by rlovell383
If I jump it with cables it spins it over like nothing. I am currently relying on the frame as my ground wire to the front which I think is my problem. Thanks guys
Where are you jumping ? (between what two points). The area between the jump spots would be the problem then as with the jumpers you are creating an easier path.

It could very well be a poor ground.

Jim

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post #7 of 12 (permalink) Old Feb 10th, 06, 04:43 PM Thread Starter
 
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Re: Voltage Drop Question

I mean jump start it with another car with jumper cables, when it dosent want to start. I guess I wasnt very clear. Thanks
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post #8 of 12 (permalink) Old Feb 10th, 06, 05:53 PM
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Re: Voltage Drop Question

What size cables are you using?

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post #9 of 12 (permalink) Old Feb 10th, 06, 06:30 PM
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Re: Voltage Drop Question

what is the motor grounded to, now that you moved the battery to the trunk?
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post #10 of 12 (permalink) Old Feb 10th, 06, 07:41 PM Thread Starter
 
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Re: Voltage Drop Question

I am using a 1/0 guage positive from the batt to the starter and remote solenoid. And a 2 guage from the batt negative to the rear subframe. I have subframe connectors. The motor is grounded with 1/2 in wide braided strap to the front subframe. Same for the body to frame.
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post #11 of 12 (permalink) Old Feb 10th, 06, 09:28 PM
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Re: Voltage Drop Question

Besides you upgrading the ground connection with the new cable that you have on order this may help the problem but I wonder too, how are the ends (terminals) attached to the 1/0 wire you have. You could have VD through them. 1/0 is a big cable and what I do on customer's cars is to crimp the terminal tight onto the wire and then use a Mapp gas torch to heat up the terminal and the wire crimped to it and then flow in solder. I'm just a fan of soldering wires and on some terminals you can partially fill the terminal with solder and then after tinning the wire end, heat the terminal end up and then shove the wire into it and after it cools it makes a joint but myself I would rather see the terminal crimped down first to limit how much solder is in there.

Another thing is I wonder if the alternator is charging up the battery enough. I have an adjustable regulator on my car with the battery in the trunk and I can dial it in to where I have 14.4 volts right at the battery terminals. I wonder if you alternator is maybe not putting out enough. When you jumped it with another car you were still using the same wires and ground paths in the car. All that was done was add more available current and voltage to crank over the starter.

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post #12 of 12 (permalink) Old Feb 10th, 06, 09:30 PM
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Re: Voltage Drop Question

Quote:
Originally Posted by rlovell383
I am using a 1/0 guage positive from the batt to the starter and remote solenoid. And a 2 guage from the batt negative to the rear subframe. I have subframe connectors. The motor is grounded with 1/2 in wide braided strap to the front subframe. Same for the body to frame.
Run a nice heavy ground wire from the battery to the engine block ! you have WAY too many connections in your ground path.
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