Well I was waiting to get the pictures done for part three but just not having much luck with time to do it. Decided the pictures don't really add that much to the post so here is part three.
Part1
https://www.fiero.nl/forum/Forum2/HTML/081542.htmlPart2
https://www.fiero.nl/forum/Forum2/HTML/081601.htmlMeters Part 3
Battery Voltage Test (continued)
The no-load battery voltage must be up to full charge value (at least 12.4 volts)
If the battery is not fully charged, battery cranking voltage tests will be inaccurate.
1.Turn the headlights on for 10 seconds to dissipate any battery surface charge.
2.Turn the lights off.
3.Set the meter function switch to Volts, 20v or greater range.
4.Hoot up the voltmeter, Red lead to + post Black lead to - post.
5.Measure the no-load battery voltage and note it. This is the rest voltage of the battery. Normal full charge no-load voltage readings are 12.6 volts.
6.A reading of less than 12.4 volts indicates the battery charge may be low or battery is failing. Recharge it before continuing the test.
Battery Test During Cranking
This test the battery’s ability to provide adequate cranking voltage and hold the voltage at a steady value during cranking.
1.Set the function switch to Volts 20v or greater.
2. Connect to battery.
3.Disable the ignition by grounding the coil secondary or by disconnecting the primary ignition circuit.
4.Crank the engine for 10 seconds while observing the battery voltage.
5.A normal cranking voltage should remain at 10 volts or higher.
The voltage should hold steady during cranking. If the battery is weak, the voltage may gradually drop during cranking.
For example, if the battery starts out cranking at 11 volts and then drops to 10 volts during the 10 seconds the battery is weak. Check your connections are clean, recharge the battery and test again. If you get the same results a new battery maybe in your future.
Cable and Connection Standards
When ever people have problems starting we always tell them to check their cables. The battery cable and connection voltage standard of 0.2 volts is the maximum allowable voltage drop at any connection on a starter circuit.
If the connection shows more than 0.2 volts during cranking, the conection or cable is BAD! The cables and connections must be cleaned or replaced.
Battery Ground Voltage (Engine)
This test checks for battery-to-engine ground voltage. The acceptad ground circuit voltage standard is 0.2 volts (200 mv) or less, during cranking.
Note: digital voltmeters must be used for ground voltage tests. Analog (needle) meters are not accurate enough for low voltage readings.
1.Set the function switch to Volts and a 2 or 20 volt scale.
2.Connect the + lead to a bolt on the engine block (be sure you pick a good connection without paint and dirt. (on the v6 I like to use the screws that hold the Map sensor, on the 4’s this is on the air cleaner and not a good choice)
3.connect the – lead to the negative battery post, NOT the terminal. (may have to have help with this)
4.Disable the ignition as noted above.
5.Crank the engine for five seconds. This will cause 100 to 200 amps of current to flow through the batter ground cable.
6.A normal engine ground voltage drop is 0.2 (200 mv) volts of less during cranking.
7.A batter ground voltage of more than 0.2 volts indicates a poor engine ground circuit. 0.3 volts is marginal. Over 0.3 is bad!
8.Clean the battery cable connection and engine block ground and test again.
9.If the ground voltage drop is still over 0.3 volts replace the cable.
Battery Ground Voltage (chassis)
The test checks for battery to chassis ground. Many circuits are grounded to chassis parts such as body panels or bulk-heads, floor pans, and frame members. Just as engine control computers must have good grounds, chassis grounds are just as important. Other vehicle lighting, window lift and computer cirsuits may be grounded to the chassis. Quite often, there are ground straps between the chassis ground, engine, and/or the batter. On the first gen. Fieros there is that “great” little ground cable from the battery – to the battery tray. (not great) There is another “great” on from the transmission to the right frame. (I have found both of these to be of questionable tightness often times).
Testing.
1.Set the meter to volts.
2.Connect the + lead to a bolt on the fender, bulk head or the vehicle frame where an accessory, tail light or good solid ground can be found. (I have used the bolts of the cruise control with good results at times. Connect the – lead to the – battery post.
3.Turn all the accessories ON (bright lights, A/C fan-high, rear window defroster, radio, etc). This will cause al least 15-20 amps of current flow, through all circuits.
4.Disable the ignition so the engine will not start. (as noted above)
5.Crank the engine for five seconds. (an additions 100-200 amps of current flow.
6.a chassis ground of less than 0.3 volt (300mv) is good. Note: this is higher than the previous quoted standard.
7.A shassis ground voltage of more than 0.4 volts indicates a poor chassis ground circuit. ( I was able to get mine to 0.3 by cleaning and adding grounds.
Battery Cable to Starter Test
This test checks the battery positive post through the cable to the starter solenoid.
1.Set the switch to volts.
2.Select the 0-2 volt scale.
3.Connect the + lead to the positive battery terminal. The – lead to the starter bolt.
4.Disable the ignition at above.
5.Crank the engine for 5 seconds.
6.A good voltage drop is less than 0.2 volts. Again if above this clean the connections or replace the cable.
Charging voltage at the Battery. (See Part 2 )
A Case History: Hard Starting, Weak Ground Circuit
When doing a tune-up on a 1986 GT, I asked the owner if it had any symptoms of hard starting. His answer was “No it seems to start OK.”
During a tune-up I measured the starter cranking voltage and the ground voltage, even when no concerns where indicated.
The cranking voltage was 10.3 volts. The battery was holding this voltage after 10 second of cranking so the battery was reasonably strong.
The cranking sound was slightly weak sounding even though the cranking voltage was meeting the minimum 10 volts.
A good will-tuned engine should start within two seconds. This one was taking about four seconds to start.
Upon further measuring, the ground voltage was a whopping 0.7 volts. This was unacceptable! Remember standard is 0.2 volts. The meant that 0.5 volts was being wasted as heat instead of supplying this voltage to the starter.
After cleaning both battery terminals the voltage drop was still 0.4 volts. This improved the cranking performance and sound, slightly.
A new ground cable was installed. Lo and behold, the total ground voltage was only 0.15 volts during cranking. The cranking voltage increased to 11.0 volts.
Well the starter now sounded energetic, and the engine started within two seconds.
The owner came back the next day and commented, “It never started so easily before!”
We become accustomed to how our cars start and don’t realize that there is a problem developing until it become a major problem. Unfortunately, in the north, that seems to happen on the coldest day of the year with the wind blowing 40 mph.
[This message has been edited by Dodgerunner (edited 04-22-2007).]
