4JB1T big voltage drop on startup

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Gibbs
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Location: Western Australia
Isuzu vehicle(s): 95 Holden Rodeo 4JB1T

4JB1T big voltage drop on startup

Postby Gibbs » Mon May 28, 2018 10:29 pm

Gday guys.
I have a starting issue with my ute atm. The battery is only a fortnight old. I had to replace the old 1 because it died trying to start the car so many times.

The new battery was ok for about a week but now I'm having the same starting issues in the morning. Once the car is started it is good for the rest of the day.

The thing that I'm noticing is that the voltage displayed on the dash drops very quickly from 12 volts right down to about 9 volts and the engine cranks slowly. However on a cold start if I attach jumper leads to my wife's car and raise the voltage to around 13V my car will turn over and start almost instantly!

The alternator seems to be doing its job also. When running the voltage almost instantly jumps up to somewhere around 14 volts.

I'm thinking a voltage leak somewhere?
Has anyone ever had a issue like this that might be able to point me to a breaker or relay that might be damaged?

Cheers
Steve

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85PUPDSL
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Re: 4JB1T big voltage drop on startup

Postby 85PUPDSL » Wed May 30, 2018 5:04 pm

Quick test: Disconnect the ground cable after using the vehicle normally for a day (battery charged). The next day, reconnect the ground cable and see if it starts right up. If so, there is a leak somewhere when the battery is connected and in the loop.

Denny
Original owner/ 85 P'up DSL NA 5-Speed Long Bed 2WD and 2018 Subaru Outback 2.5 Limited

Gibbs
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Posts: 6
Joined: Tue May 22, 2018 2:01 am
Location: Western Australia
Isuzu vehicle(s): 95 Holden Rodeo 4JB1T

Re: 4JB1T big voltage drop on startup

Postby Gibbs » Wed May 30, 2018 9:37 pm

Thanks for the tip mate. I'll give that a go.
Iv got my battery out atm to check the cables and earth from the battery is a little green in places so I might get a new cable. Iv also looked at the positive cables on the battery side and some of those are looking a bit green also.

Gibbs
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Posts: 6
Joined: Tue May 22, 2018 2:01 am
Location: Western Australia
Isuzu vehicle(s): 95 Holden Rodeo 4JB1T

Re: 4JB1T big voltage drop on startup

Postby Gibbs » Thu May 31, 2018 11:17 pm

Disconnecting the ground cable definitely made a difference. Voltage sat up around 12.5 - 13 volts when key was turned and the car started on 1st turn after 3 or 4 seconds. It was cold overnight so I'm happy with that.

I think I might start by replacing the major cables running from the battery and keep working my way back.

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85PUPDSL
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Re: 4JB1T big voltage drop on startup

Postby 85PUPDSL » Fri Jun 01, 2018 10:41 am

Disconnect the neg batt cable and put an ammeter in-line between the disconnected cable term and the battery post to see how much leakage you have. Start pulling fuses one at a time until no leakage shows. That will give you a clue what circuit and what is on that circuit that is causing the leakage.

Denny
Original owner/ 85 P'up DSL NA 5-Speed Long Bed 2WD and 2018 Subaru Outback 2.5 Limited

Gibbs
Regular Member
Posts: 6
Joined: Tue May 22, 2018 2:01 am
Location: Western Australia
Isuzu vehicle(s): 95 Holden Rodeo 4JB1T

Re: 4JB1T big voltage drop on startup

Postby Gibbs » Fri Jun 01, 2018 11:19 pm

Electrics are so interesting!

When I disconnected the neg terminal and set up my multimeter it displays 0.20 on the digital display. Funny thing is something would then cycle from somewhere in the dash or at the back of the engine and I would get a spike of up to 0.40 and then it fade out to 0.01 once the cycle completed after a few seconds. Seems super strange that there is a leak of some sort but it then cycled itself out. I get this same cycle when I reconnect the battery terminals.

I traced this back to the interior light. Not sure if it is original because it is LED. Now that's a head scratcher. I think it might be easier to just live without an interior light.

Anyhow I will take the ute for a spin later to get the volts up and leave battery connected overnight to see if she cranks up. She started up for the second straight morning disconnecting the neg so hopefully this case is close to solved

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Quahlity
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Re: 4JB1T big voltage drop on startup

Postby Quahlity » Sat Jun 02, 2018 10:38 am

Be sure to check the ground between the frame and the engine. It can cause weird problems if it becomes disconnected. A simple test would be to ground the engine to the frame with a jumper cable.

Gibbs
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Joined: Tue May 22, 2018 2:01 am
Location: Western Australia
Isuzu vehicle(s): 95 Holden Rodeo 4JB1T

Re: 4JB1T big voltage drop on startup

Postby Gibbs » Mon Jun 04, 2018 4:02 am

I will check the ground to see what happening there. I did sand back the ground connection back to metal because that part ofnthe chassis was painted for some reason. I plan on replacing the entire grounding cables because they are a little green.

Car has now started 4 mornings straight without an issue, the last 2 mornings with the battery hooked up so fingers crossed.


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