Testing Slow Cranking Speed Problems

Evaluating Grounds and Battery Wiring

Quality of your vehicle main wiring, as well as cranking problems, can be isolated through a few quick, simple, measurements. All that is needed is a simple inexpensive digital volt meter, a clip lead or two to attach the probes, and someone to crank the car while you read voltages. With a few basic readings, you can use an Excel sheet I made to evaluate both grounding and battery wiring.

Ignore any negative sign and just record the absolute voltage. Use the lowest meter scale possible. Use a clip lead if necessary to assist you in holding a connection. In my car, the starter current is over 350 amperes on initial hit. The start current quickly drops to about 175 amperes after the engine starts spinning. Record the steady voltage as it spins, not the initial hit.

Measured While Cranking (unless noted)

  1.  Voltage from the probe placed on physical center point on battery negative post to vehicle chassis on the opposite side of vehicle is ____________ volts. This measures battery grounding. Lower is better, should be less than 0.5 volts.

  2.  Voltage from the physical center point on battery positive post to chassis opposite side of vehicle is no crank ______ to cranking ______ volts. This measures battery charge (no crank should be over 12.5 volts at full charge) and cranking supply voltage (should be over 10.2 volts with a good battery).

  3.  Voltage from the engine block or manifold to vehicle chassis away from, and forward of, any engine ground points is ____________ volts. This measures block grounding, and should be less than 0.5 volts.

  4.  Voltage from the starter solenoid battery terminal post terminal stud to the vehicle chassis is ____________ volts. This is voltage available for starter at relay, and should be over 10.5 volts for best starting.

  5. Voltage from the starter positive post stud to bell housing or block is ____________ volts. This measures actual starter voltage, and should be over 10 volts.

 

Note: Download the Excel page, and edit only the Green areas!!

My car results using Excel sheet are shown. You can see my wiring results.  Download Excel sheet CLICK HERE

Starter Evaluation            
   
B- to chassis B+ to chassis (no crk) B+ to chassis crnkg Block to chassis Start Sol + to chas Starter to block  
0.27 12.5 11.18 0.2 10.91 10.65  
   
Battery 12.5 charged bat  
Battery loaded 11.45 good bat  
Battery ground 0.27 good  
Block Ground 0.2 good  
Battery Lead drop 0.27 good  
Solenoid to starter 0.06 good  
Ground drop 0.00 good  
   
Note: If multiple results are bad, starter could be drawing excessive current. Normal start current is less than 200 amperes. This requires a special test meter.

  

 

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