|
|
Losing voltage while cranking
|
|
|
| |
|
|
Moesouraya
Novice
Nov 16, 2015, 6:10 PM
Post #1 of 13
(1680 views)
|
|
Losing voltage while cranking
|
Sign In
|
|
Hi guys. So I have a 1987 bmw e30 I swapped the engine with a rb25. The problem I'm having is when I try and start the car my voltage drops down to around 7 volts and then continues to drop. Compression is good I have fuel I have spark. I checked and rechecked my wiring a bunch of times and I did have the car started before. So what could cause my voltage to drop so much.
And I have tried charging the battery and boosting the car as well. I will get 14 volts while the jumpers are connected but as soon as I try and start it I lose it all.
Can someone please help.
|
|
| |
|
|
Discretesignals
Ultimate Carjunky
/ Moderator
Nov 16, 2015, 6:23 PM
Post #2 of 13
(1674 views)
|
|
Re: Losing voltage while cranking
|
Sign In
|
|
Where are you measuring the voltage at?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
|
|
| |
|
|
Moesouraya
Novice
Nov 16, 2015, 7:36 PM
Post #3 of 13
(1658 views)
|
|
Re: Losing voltage while cranking
|
Sign In
|
|
I installed gauge.
And the car also sounds like it's losing voltage.
|
|
| |
|
|
Discretesignals
Ultimate Carjunky
/ Moderator
Nov 16, 2015, 7:40 PM
Post #4 of 13
(1654 views)
|
|
Re: Losing voltage while cranking
|
Sign In
|
|
Do you have a multi-meter? If so, measure the voltage on the battery posts with the key off and then measure the voltage on the battery posts with the engine cranking. What are the readings?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
|
|
| |
|
|
Moesouraya
Novice
Nov 16, 2015, 8:31 PM
Post #5 of 13
(1650 views)
|
|
Re: Losing voltage while cranking
|
Sign In
|
|
Ok I'll will do that tomorrow and let you know. Do you think it could be just a really bad battery?
|
|
| |
|
|
Moesouraya
Novice
Nov 17, 2015, 8:17 PM
Post #6 of 13
(1625 views)
|
|
Re: Losing voltage while cranking
|
Sign In
|
|
So I did the test 11.2 then while I'm cranking it drops to 2.7. And I also tested while boosting the battery it was 14 volts and while I was cranking it dropped to 5.9 and kept dropping. So what do you think.
|
|
| |
|
|
Tom Greenleaf
Ultimate Carjunky
/ Moderator
Nov 18, 2015, 12:24 AM
Post #7 of 13
(1621 views)
|
|
Re: Losing voltage while cranking
|
Sign In
|
|
Where are you checking exactly? Top post battery no doubt so are you checking the post or the "U" bolt that clamps to it? Do both while cranking and when not.
With a boost if it truly dropped that low starter is working way too hard, would or should go to rapid fire clicking of solenoid or wires get hot somewhere.
If you have all know how to re-enable any anti-theft or other control you should be able to start this car without it's own battery but requires super quality jumper cables most don't have for more info and check battery when charged up out of the car.
Is this battery in trunk or under back seat or something? Watch out if so. Those must have vents to outside of car which should come with a new proper battery or be in place now. That is for the gasses it could make if battery is not open to air like under the hood only and NOT the problem at hand but a total must to have or high risk of explosion! Know that,
T
|
|
| |
|
|
Discretesignals
Ultimate Carjunky
/ Moderator
Nov 18, 2015, 5:26 AM
Post #8 of 13
(1614 views)
|
|
Re: Losing voltage while cranking
|
Sign In
|
|
If you measured that at the battery posts, that battery is bad or you have a poor battery terminal connections. I'd say it is time to try a good known battery and see what happens. I've seen batteries shorted out internally that jumping wouldn't get the vehicle started.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Nov 18, 2015, 5:27 AM)
|
|
| |
|
|
Tom Greenleaf
Ultimate Carjunky
/ Moderator
Nov 18, 2015, 6:21 AM
Post #9 of 13
(1611 views)
|
|
Re: Losing voltage while cranking
|
Sign In
|
|
Better said than intended DS - thanks. OP, this smacks of bad connection even if it looks good. Testing volt drop while cranking is useful info at battery itself and the clamp.
The jumper cables I speak of are not easily available for power enough without a battery in low state so get another known good one as mentioned by DS. Batteries absolutely do short out inside. Tell tale is low volts when fully charged on a bench even after a good charge it's discharging itself just sitting there. At that point I put those OUTDOORS out of harm's way!
Other: Can't think of a reasonable way to "memory save" a battery in this being disconnected which is why you should really know any tricks of features it probably has even this old that require reprogramming. Radio, even some brakes maybe etc.,
T
|
|
| |
|
|
Hammer Time
Ultimate Carjunky
/ Moderator
Nov 18, 2015, 6:25 AM
Post #10 of 13
(1608 views)
|
|
Re: Losing voltage while cranking
|
Sign In
|
|
It's a 1987. I don't think you have much programming loss to worry about.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
|
|
| |
|
|
Tom Greenleaf
Ultimate Carjunky
/ Moderator
Nov 18, 2015, 6:28 AM
Post #11 of 13
(1603 views)
|
|
Re: Losing voltage while cranking
|
Sign In
|
|
OE Radio does even older than this, '87 BMW - it may think it's being stolen? T
|
|
| |
|
|
Moesouraya
Novice
Nov 18, 2015, 9:50 AM
Post #12 of 13
(1593 views)
|
|
Re: Losing voltage while cranking
|
Sign In
|
|
Thanks for you help guys. I will get a new battery today and keep you posted.
|
|
| |
|
|
Tom Greenleaf
Ultimate Carjunky
/ Moderator
Nov 18, 2015, 10:12 AM
Post #13 of 13
(1589 views)
|
|
Re: Losing voltage while cranking
|
Sign In
|
|
Suggestion: Go quality and find out if encrypted how old new one is. Place will know for sure. I just saw a mid 2014 being sold new on the shelf just peeking. They age from date filled not the day you buy or use it. Suggest less than 3 Mo. or so is possible if you wait a day to request that.
Sounds silly but new batteries are NOT fully charged! Charge it first on the bench so it should rule the dang thing out totally,
T
|
|
| |
|
Auto Repair Home
SEARCH
WHO'S 
LOG 
Drive Shaft Repair
2006 Toyoto Camry XLE Driver Side Electric Window Trouble
Grounding Cable, 2017 Jeep Renegade Trailhawk
equipment
Howdy
