Voltage drop during cranking
#1
Voltage drop during cranking
This is the story, i was getting pretty slow cranks recently, so i had my buddy check the volts while i cranked my car over and it dropped around 8.2 volts, so i assumed it was my battery and decided to relocate my battery at the same time. So i relocated the new battery behind my pass. Seat in the tub and i am still having slow cranking issues, now when i crank its around 8.7. It still starts fine but it floods easier now and id like to avoid this if possible. Any help is appreciated.
#2
Are you experienced?
iTrader: (18)
check positive cable to starter (and negative cable going under the oil filter bolted to the engine/bellhousing bolt) and battery terminals. look for corrosion and loose cables.
something ill let you read:
http://www.aa1car.com/library/voltage_drop_testing.htm
something ill let you read:
http://www.aa1car.com/library/voltage_drop_testing.htm
#3
whats going on?
iTrader: (1)
so you decided your battery was bad, purchased a new battery but then decided "**** it" and throw it in the storage bin? did you not at least check out the new battery first? or check to see if the fault is your wireing? you introduced more variables into your problem.
#4
Rotary Freak
All our cars have a large voltage drop when the starter is engaged. I'm pretty sure mine drop into the 8-9 volt range when the starter is engaged. Normal to me. Starters require a lot of amps/voltage when turning an engine over.
Go have your friend monitor the voltage drop on his Yugo when starting. I bet it drops low also when the starter is engaged.
Go have your friend monitor the voltage drop on his Yugo when starting. I bet it drops low also when the starter is engaged.
#7
My battery was a 4 year old valuecrap battery so yea i assumed it was dead and replaced it. my plugs and wires are brand new, i just replaced them, and my old battery cables were all chewed up and had the wires exposed and some parts were rusty or corroeding, so that was my main reason for relocating it. I should check my engine ground, its probably overdue for replacement. I have a new battery, with new terminals, the ground is a 9 gage wire for about 8 inches to the bolt hole in the tub area, my positive is a 5 gage wire for about 8 inches into a 100amp circuit breaker and then the 5 gage countinues to the engine bay when it splits into another 9 gage for about 8 inches to the main fuse box, and another 9 gage wire for about a foot then i have it connected to the power wire that went to the starter.
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#9
Sharp Claws
iTrader: (30)
8.7volts is a little low but ~9v during cranking is pretty common and normal.
relocating the battery was a bad idea in an effort to diagnosing a slow cranking issue, you introduced more resistance into the starter system with longer battery cables... the end result is actually less cranking volts, hence even slower cranking on a car with the same starter/battery.
if you want faster cranking the opposite is what you should have attemped to accomplish which is the shortest large gauge wiring to the starter as possible, the stock battery location is as close to the starter as you can physically move a full sized battery to. also the battery itself has an effect on cranking speeds, smaller utility batteries like some people put in that are made for watercraft for example, have less cold cranking amps and less reserve battery power than larger batteries do. the larger the battery is, generally, the faster and longer it will turn the starter. thicker battery cables will do the same also, by allowing current to flow more easily. smaller longer battery cables do the reverse, they bottleneck the current flow which results in slower cranking speeds and the cables themselves will start to get hot from it.
the negative terminal on the car should be as short as possible to a solid chassis ground and then you can "spider web" the ground cables to the rest of the car from there. i would run a ground cable directly to the starter from your main grounding point though, which will allow it a more direct path to the battery(also basically how the original negative battery cable was routed/designed). you basically can't have too many ground cables to various points on the car.
relocating the battery was a bad idea in an effort to diagnosing a slow cranking issue, you introduced more resistance into the starter system with longer battery cables... the end result is actually less cranking volts, hence even slower cranking on a car with the same starter/battery.
if you want faster cranking the opposite is what you should have attemped to accomplish which is the shortest large gauge wiring to the starter as possible, the stock battery location is as close to the starter as you can physically move a full sized battery to. also the battery itself has an effect on cranking speeds, smaller utility batteries like some people put in that are made for watercraft for example, have less cold cranking amps and less reserve battery power than larger batteries do. the larger the battery is, generally, the faster and longer it will turn the starter. thicker battery cables will do the same also, by allowing current to flow more easily. smaller longer battery cables do the reverse, they bottleneck the current flow which results in slower cranking speeds and the cables themselves will start to get hot from it.
the negative terminal on the car should be as short as possible to a solid chassis ground and then you can "spider web" the ground cables to the rest of the car from there. i would run a ground cable directly to the starter from your main grounding point though, which will allow it a more direct path to the battery(also basically how the original negative battery cable was routed/designed). you basically can't have too many ground cables to various points on the car.
Last edited by RotaryEvolution; 03-17-11 at 07:02 PM.
#12
Rotary Enthusiast
iTrader: (19)
Im having these same issues with my rebuilt engine, i cannot seem to start her up ive tried 2 batteries, an interstate with 800cca and an optima redtop... the result however were the same, i got the starter tester and passed... it is a fresh rebuild and im wondering what the issue is i checked the ground cable and it seemed to get warm hot to the touch, while i cranked the car...its an s4 turbo II engine.... stock ecu 550 660 secondaries, ported turbo, i am using the NA wiring harness.
any suggestions???
im going to get the alternator tested tomorrow as well
any suggestions???
im going to get the alternator tested tomorrow as well
#13
whats going on?
iTrader: (1)
Im having these same issues with my rebuilt engine, i cannot seem to start her up ive tried 2 batteries, an interstate with 800cca and an optima redtop... the result however were the same, i got the starter tester and passed... it is a fresh rebuild and im wondering what the issue is i checked the ground cable and it seemed to get warm hot to the touch, while i cranked the car...its an s4 turbo II engine.... stock ecu 550 660 secondaries, ported turbo, i am using the NA wiring harness.
any suggestions???
im going to get the alternator tested tomorrow as well
any suggestions???
im going to get the alternator tested tomorrow as well
#14
Retired Moderator, RIP
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I hope that the New battery is a gel cell type battery(like Optima) and not a acid type battery.If you relocated the battery to the inside,the battery would be putting out fumes(if it was the old type).
#15
Rotary Enthusiast
iTrader: (19)
thats the way its set up, ibjust ran an extra ground from the other side of the longest starter bolt to the strut tower. im stumped. i tried the battery off my other rx7 and it did the same... i got my alternator tested and its in great shape! how can i cldtart breaking the issue down? i checked the main harness ground and in going to take it off and scrape it clean for a better ground....
#16
Rotary Enthusiast
iTrader: (19)
the battery is not relocated, its in its stock location its just acting up... there's a draw somewhere...i just checked the wiring to the battery and starter i even cleaned the main ground on the strut tower again and used a fresh ground bolt too. again its a TUrbo swapped GXL using the NA wiring harness with emissions deleted. on the ecu i Pulled 3 wires one from each plug, but i dont know if i the ones that I TRIED to pull where the correct ones for the swap. the ones i tried to pull are the power steering wire which is the knock sensor for the Turbo model (Pin 1R), I also pulled pin 2k(split air solenoid on NAs, but for the twin-scroll solenoid on turbos) and pin 3d(fuel pump resistor/relay on turbos, but is unused on manual NA)...
with that said the wires i pulled where:
The Light green wire with the black stripe off the biggest plug which is a 24 pin; then the Blue wire with a black stripe off the 18 pin harness; and finally the black wire with the red stripe off the smallest plug which is a 10pin( the injector plug)...
with that said the wires i pulled where:
The Light green wire with the black stripe off the biggest plug which is a 24 pin; then the Blue wire with a black stripe off the 18 pin harness; and finally the black wire with the red stripe off the smallest plug which is a 10pin( the injector plug)...
#20
Rotary Enthusiast
iTrader: (19)
i put a volt meter on the cables and seemed to be working fine.... i had some one turn the ignition on and start the car the see if there was some kind of a load and it seemed fine i had 12.15 volts on at the battery and 11.26-11.8 down at the wires... is that too much loss?
#23
Rotary Enthusiast
iTrader: (19)
okay i bought a new optima, new starter, new terminals and added; the volts drop while cranking to 6-8 volts....and the car cranks a tad bit faster but yet has a bit of a lag still. i finally got it to fire up, it was on running at 3k rpm for about 30 seconds and it died, i was able to start it up again for 5 seconds then it died again....i checked the wiring everything looks fine,
im running 550/660cc injectors, walbro 255 and all stock turbo parts...i pulled the 1r pin off the ecu and thats it...need help guys i want to move this car out of my driveway!
im running 550/660cc injectors, walbro 255 and all stock turbo parts...i pulled the 1r pin off the ecu and thats it...need help guys i want to move this car out of my driveway!
#24
I wish I was driving!
My battery was a 4 year old valuecrap battery so yea i assumed it was dead and replaced it. my plugs and wires are brand new, i just replaced them, and my old battery cables were all chewed up and had the wires exposed and some parts were rusty or corroeding, so that was my main reason for relocating it. I should check my engine ground, its probably overdue for replacement. I have a new battery, with new terminals, the ground is a 9 gage wire for about 8 inches to the bolt hole in the tub area, my positive is a 5 gage wire for about 8 inches into a 100amp circuit breaker and then the 5 gage countinues to the engine bay when it splits into another 9 gage for about 8 inches to the main fuse box, and another 9 gage wire for about a foot then i have it connected to the power wire that went to the starter.
Regardless, its too small.