Battery power (voltage) level drops below level to crank engine

billr

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Energizing the starter motor is plenty enough load to check for a poor ground from battery to engine; no need to turn on anything else. Yes, always have the battery charged to 12.6V, or more, for testing. Voltage at the battery terminals should not drop below 11V while the cranking load is applied. Remind me, does this not crank at all, no motion of the engine? Even at 10.8V the engine should rotate slowly.
 

josiah

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billr,
Notes->
(1) battery posts and cables appear clean enough.
(2) For all tests below the engine never cranked. Maybe a 2 clicks clicks at first but after that nothing.
(3) And I made sure the selector was in PARK.

7/6 recharged battery to 13-14 volts.
Did tests second time. Please see replies in red below.

Test 1->if this is a top-post battery, then try twisting the posts when cable are off. Those posts should have no looseness in the battery.
Result->This is a top posts battery; and posts are tight.

Test 2-> Read voltage from battery negative terminal to engine block.
How I did test->start at negative battery terminal->through extension#1->through multi-meter->through extension#2->end at motor block (just below valve cover).
Result->voltage=0.
My comment->I thought 0 voltage would be expected since there should be no current. If I am wrong please inform me.

Test 3->Read voltage from battery positive terminal to engine.
How I did test->Routed same as test#2 above except started at positive battery terminal and ended at motor block.
Result->Voltage before turning ignition key->minus 14.34(I think this is minus only because the current routed through the meter in reverse; I think this is ok). Voltage after turning ignition key->minus 2-5 volts (really fluctuates).

Test 4-> Read voltage at battery end of the big positive cable.
How I did test->Routed same as test#2 above except started at positive battery terminal and ended at battery negative terminal.
Result->Before turning key voltage=high 11s-low12s (fluctuated). After turning key voltage=5.40

Test 5-> Do same at end of that cable that connects to the starter.
How I did test->Routed same as test#2 above except started at negative battery terminal and ended at starter connector bolt.
Result->Before turning key voltage=12-13 (fluctuated). After turning key voltage=2-3

Test 6> If there is a big power contact connecting the battery to starter, read at both sides of that contactor.
Result-> I did not find contactor.

Thanks, Joe
 
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billr

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Test #4 is the definitive one, if voltage is dropping from the 11-12V range down to 5.4V when you turn the key trying to crank, then the battery is probably bad. There is a slight chance there is a short in the starter that is sucking the battery down abnormally, but not likely. If you still don't trust a FLAPS to do a (free) load-test on the battery, try a battery from a different car or boost cables from another car or try the "start" boost function on you charger, if it has one. If any of those provide some cranking, then your battery is almost certainly bad. Frankly, the fact that the battery quickly dropped down from 14V to 11-12V in this process is another hint the battery is bad. What is the year code on the battery? That is another clue, batteries only last 5-10 years at best. If it is even approaching 5 years, it is likely to be tired.

As to test #2; yes you should get near-zero volts between bat negative and engine if the grounding is OK. But not because there is no current, because a good ground will provide very low resistance. The current, when cranking should be well above 100A.
 

grcauto

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Test #4 is the definitive one, if voltage is dropping from the 11-12V range down to 5.4V when you turn the key trying to crank, then the battery is probably bad. There is a slight chance there is a short in the starter that is sucking the battery down abnormally, but not likely. If you still don't trust a FLAPS to do a (free) load-test on the battery, try a battery from a different car or boost cables from another car or try the "start" boost function on you charger, if it has one. If any of those provide some cranking, then your battery is almost certainly bad. Frankly, the fact that the battery quickly dropped down from 14V to 11-12V in this process is another hint the battery is bad. What is the year code on the battery? That is another clue, batteries only last 5-10 years at best. If it is even approaching 5 years, it is likely to be tired.

As to test #2; yes you should get near-zero volts between bat negative and engine if the grounding is OK. But not because there is no current, because a good ground will provide very low resistance. The current, when cranking should be well above 100A.
If you were to short the battery out with a metal bar it would not drop voltage to that level for several seconds. That much current through even a battery cable will smoke in just a few seconds.
 

josiah

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Billr,
Your question above->" If you still don't trust a FLAPS to do a (free) load-test on the battery, try a battery from a different car or boost cables from another car or try the "start" boost function on you charger, if it has one".

Reply-> The only available battery is in my wife's suv, but I better not (chicken).
Yes my battery charger has a start function but I have NEVER used it to start a car (chicken again). I will decide to use the charger, if you are sure it won't harm the ole car, or jump it. Or when time allows I plan to pick up a new battery at Walmart or used at PicknPull.
Or I may even go ahead and take battery to parts store, get free test, they will tell me it's bad and then try to sell me a new one;: all I lose is time.

grc,
Your question above-> "what is the year code"

Reply->8/17

I plan to let know that happens.

Thanks for your help, Joe
 

billr

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Trying a different battery would be safer than using the charger's "start" function. I have used the "start" with no problem for many years, but know output has a lot more AC ripple on "start", with peaks that get up well past 15V. Neither the ripple or higher voltage should be a problem for well-designed auto systems, but who can be sure if a specific M/M/Y vehicle is "well-designed"???
 

josiah

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bill and Grcauto

billr, now I wish I read your last message because this morning I tried to crank engine using the charger start engine function and it DID NOT crank.
But now I have another problem no power seems to be coming from the battery, and it does have voltage. Inside that are no dashboard lights, nothing. As. If no battery in car but there is.

please help. Thanks joe
 

billr

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Don't panic, I doubt you hurt anything trying the charger-start. More likely is that you forced a poor wiring connection to become an open connection. Actually, that is good news; as now it should be easy to find.

You have about 12V at the battery terminals, correct? Turn on the head-light switch and verify the lights don't come on but you still have 12V at the battery terminals. If the battery voltage has dropped way down (to what voltage???) then the battery is bad. Otherwise, it is a wiring problem.

With the head-lights "on", check voltage between the battery negative terminal and several places that are supposed to be ground; like the engine block/head and car frame. These should all be near-zero volts.

Then, if the grounding is OK, check voltage relative to ground at the battery cable terminal where it connects to battery, then where the cable connects to the starter. Again, with head-lights "on" to provide a load on the system. I think you will quickly find a bad battery cable.
 

josiah

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billr,

thanks for attempting to warn me about using the charger start engine. i wish I had read it sooner. now I wonder what did I do wrong with the charger.

answers to your questions below:

voltage at battery=14+
turned on headlights=no headlights
after turning on headlights voltage at battery=same appx 14+
voltage between battery negative to engine block=0
voltage between battery cable where it connects negative battery post to the starter nut (located on starter side)=up to 4.6. Please let me know if I did test incorrectly.

question. The battery appears to have a fuse compartment near the positive terminal contains 3 fuses. Is lt possible a fuse blew?

thanks, joe
 

grcauto

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billr,

thanks for attempting to warn me about using the charger start engine. i wish I had read it sooner. now I wonder what did I do wrong with the charger.

answers to your questions below:

voltage at battery=14+
turned on headlights=no headlights
after turning on headlights voltage at battery=same appx 14+
voltage between battery negative to engine block=0
voltage between battery cable where it connects negative battery post to the starter nut (located on starter side)=up to 4.6. Please let me know if I did test incorrectly.

question. The battery appears to have a fuse compartment near the positive terminal contains 3 fuses. Is lt possible a fuse blew?

thanks, joe
Negative to the starter?
 

billr

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Post a picture showing all the wire/cable connections to the starter. We are confused because there is usually is no discrete ground wire to the starter, it grounds through the engine block.
 

josiah

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Billr,
appreciate the reply. I think have access to the tech but do not know how to send picture.
But the starter has 2 connectors that I can see. one wire clips into a plastic connector on starter side. Next, just below, there is the other thicker stiff wire held to starter with a nut. The the thick wire I assume is the current; and other wire above I do not know what it does.
above you mentioned you were confused regarding ”there is no ground wire to starter”. I do not recall that I said there was A ground wire to the starter. I know nothing about a ground wire to the starter.
also if I said anything confusing to you please let me know And I will re-check.
thanks, joe
 

billr

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"...cable where it connects negative battery post to the starter ..." (reply #24)

That statement. The negative battery post is connected to ground on most vehicles; probably this one too. There should be a large cable from the positive battery terminal to the starter, and a small wire to the starter that is energized only when cranking.
 

josiah

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Billr,
Basically, I was trying to say in reply#24 was that ->I took volt reading between the battery negative post to the starter(nut on side).
I edited #24 to make it hopefully clearer.

In my replies to you I try to be complete,that is not just providing the volt readings but how I got them ; however in some cases I may have said too much .Please pardon.
Any further confusion regarding my replies, please let me know.
thanks,joe
 
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