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Old 08-15-2012, 11:31 PM   #1
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Default Battery Voltage Question

1995 Bonne SE

Quick question...
With the car running what should the voltage be at the battery? I tested and voltage fluctuated quite a bit but seemed to settle in very low at around 9.4v Battery is a good one and is about a year old but I plan on having it load tested so I can rule it out. Cables were cleaned and in good condition also.

Another question...possibly related??
I had to change out the factory fuel pump last month (went 220,000 miles!) with a Carter. Within 3 days anytime I ran the a/c the pump would start to howl loudly. I noticed that my voltage dropped every time this happened. I swapped out the Carter with another one, same thing. Decided to get a Delco pump, no howling so far (been about a week) but I haven't needed the a/c much. Thoughts???

Is it possible that a failing alternator could cause the fuel pump to fail?

Thanks in advance

Drew
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Old 08-16-2012, 07:44 AM   #2
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dont beleive your gauge for exact numbers but measured with a meter at the battery it can be from 13.5 for a battery that is pretty charged been running for a while to 14.5 if you just cold started.

some of the poor quality pumps make a bunch of noise. i woulnt buy anything but delco fuel pump for gm.
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Old 08-16-2012, 09:06 AM   #3
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Should be 13.5 to 14.5 volts. Pull the alternator and have Autozone test it, but it sounds like that is the problem. A failing alternator and the resulting low voltage will cause a fuel pump to underperform, but should not cause it to fail.
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Old 08-19-2012, 01:45 PM   #4
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UPDATE

Ok, so I pulled the alternator and had it tested, checked out good in 4 tests (guy at Autozone wanted to test multiple times to be sure)

Pulled battery for load test, cleaned the cables and connections again. Load test on battery showed battery was good too.

Reinstalled, still slow starting. Sounds like when the battery is low. Retested voltage after putting new batteries in multimeter. Now I can get good readings that don't bounce around as much. With car running it'* at 13.5 - 14.3 at the battery. With Car not running battery is at 12.6v.

I'm guessing the starter'* bad, probably drawing too much power. Going to have it tested today. Any other ideas?

Drew
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Old 08-19-2012, 07:13 PM   #5
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High resistance in the cables.
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Old 08-20-2012, 01:07 AM   #6
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You would be surprised what problems a loose batt connection or even corroded cables can cause. You might have corrosion inside the cables that you can't see unless you strip the insulation off. I had all kinds of electrical problems in my Bonnie and they were all solved when I replaced all of the cables in my charging system, I would even upgrade to larger cables for less resistance
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Old 08-20-2012, 10:43 AM   #7
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Do this test, a starting system voltage drop test.



All reading should be in DC Volts, and nothing should be higher than 200 milivolts (0.2 volts). All tests have to be done while cranking the car, so disable the fuel system so that it will not start.
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Old 08-20-2012, 11:12 AM   #8
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UPDATE FIXED

Pulled the starter and took it in to Autozone for a test. It passed the test but sounded weak, I decided to pick up a new one and some new cables. Removed existing cables and they looked to be in good condition, reinstalled. Tested old starter with it not installed, again sounded weak but did "function". Hooked up new starter and noticed a huge difference, gear was spinning at a significantly higher speed and engaged faster. Installed new starter and now it'* good as new.

Thanks to everyone for your help and ideas.

Drew
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Old 08-20-2012, 11:14 AM   #9
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Did you turn your old starter in for core, or did you keep it?

Glad to hear you got it fixed.
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Old 08-20-2012, 07:38 PM   #10
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Glad you got it figured out!
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