Issues with Starting (Page 1/2)
87PontiacFGT NOV 19, 04:19 PM
For the past few months I've been replacing my dashboard, which includes, in my case, disconnecting and removing the instrument cluster. While the cluster has been worked on, I decided to try to start the car to attempt to burp any air out from a coolant change, and I just got really loud speaker buzz. It didn't make sense for the car to not run without the instrument panel, but I plugged nearly everything back in, and while it isn't as bad, it still really doesn't want to start. You can hear the solenoid clicking, and its attempting to crank, but something else is obviously taking power. I've looked at the starter circuit diagram, but I cannot tell what the problem. I even plugged the battery up to a 12v, 200 starting amp battery box, and it doesn't really help. A short video I took of the starting attempt is linked.

https://youtube.com/shorts/...dJKHLY?feature=share

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In a world where you can be anything, be a financially unstable owner of a pile of fiberglass titled; “Pontiac Fiero GT”

Vintage-Nut NOV 19, 07:44 PM
Did you measure the battery, and it has 12.8 volts or better?
theogre NOV 19, 09:25 PM
The engine doesn't need the Dash to run.

Sound system is picking up 60hz AC power noise from something & hard to hear anything else.

As to "Dead" battery.... see https://web.archive.org/web...ierocave/battery.htm
If the starter is/was Good... low or "dead" battery can wreck the starter & cables because tries to pull more amps to makeup for low volts. see Electric Motors page too.

If you have bad battery charger or anything plugged to wall outlet connected to car can cause that noise & way worse like killing the ECM & nearly all electronic parts.
Or sound system is just On & picking that from whatever.

Not sure what you use as "I even plugged the battery up to a 12v, 200 starting amp battery box, "...
Many old 120VAC charger/boosters are bad for several reasons & AC gets out from them. Many die because people use them wrong & rectifier etc can Fail shorted & AC gets out to wreck the battery & more.

Most "portable" Battery boxes uses "gell cell" lead battery & don't work after a year or three many because the battery are bad even if may put out "12v." Only in last few years small units have LiIon batteries but they have their own problems.

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(Jurassic Park)

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87PontiacFGT NOV 19, 09:38 PM
The battery itself reads at about 11.7 volts, but this vehicle has always had a habit of killing batteries. With the battery charger hooked up like it was when I tried to start it, it was reaching a steady 13.7 volts.
87PontiacFGT NOV 19, 09:45 PM

quote
Originally posted by theogre:

The engine doesn't need the Dash to run.

Sound system is picking up 60hz AC power noise from something & hard to hear anything else.

As to "Dead" battery.... see https://web.archive.org/web...ierocave/battery.htm
If the starter is/was Good... low or "dead" battery can wreck the starter & cables because tries to pull more amps to makeup for low volts. see Electric Motors page too.

If you have bad battery charger or anything plugged to wall outlet connected to car can cause that noise & way worse like killing the ECM & nearly all electronic parts.
Or sound system is just On & picking that from whatever.

Not sure what you use as "I even plugged the battery up to a 12v, 200 starting amp battery box, "...
Many old 120VAC charger/boosters are bad for several reasons & AC gets out from them. Many die because people use them wrong & rectifier etc can Fail shorted & AC gets out to wreck the battery & more.

Most "portable" Battery boxes uses "gell cell" lead battery & don't work after a year or three many because the battery are bad even if may put out "12v." Only in last few years small units have LiIon batteries but they have their own problems.




I used an old wall charger, which I've used before to start the car, and the vehicle doesn't start without it at the moment, since the battery isn't doing the best, even though its only about a year old. I'll hook it up to the charger, off the car, and see if I can't get it back up to a better voltage.
If the charger essentially just shot a bunch of the electronics, what's a good sign I can look for?
theogre NOV 20, 12:44 AM
any Charger needs 13.5-14.7 DC volts. No AC volts.
Most "dump" "dumb" chargers just has transformer & rectifier & optionally a meter. Little or nothing to smooth out the DC like capacitors because of batteries don't need it.
"Smart" chargers add "logic" like won't charge a "dead" battery < ~ 11-11.5 volts that can cause dangerous problems.

New battery won't last long because ECM etc uses some power 24/7 & will kill it after days to a couple weeks deepening on battery type etc. You might charge it after but damage is done & never work @ 100%.

[This message has been edited by theogre (edited 11-20-2023).]

Vintage-Nut NOV 20, 10:07 PM

quote
87PontiacFGT:
The battery itself reads at about 11.7 volts...



First, slowly charge the battery (~12 hours)
If the battery won't hold 12.5 volts (or higher) AFTER fully charged, it is dead.....

I suggest checking the generator/alternator output if "the vehicle has always had a habit of killing batteries".
87PontiacFGT NOV 20, 10:21 PM

quote
Originally posted by Vintage-Nut:


First, slowly charge the battery (~12 hours)
If the battery won't hold 12.5 volts (or higher) AFTER fully charged, it is dead.....

I suggest checking the generator/alternator output if "the vehicle has always had a habit of killing batteries".



After taking it off the vehicle and putting it on a trickle charge for a little under 24 hours, I got it to around 12.5/12.4 volts. I put it back in the vehicle, and it started as well as a vehicle sitting for several months should start. I don't suspect the alternator to be the problem, since the battery usually dies after the vehicle sits for over a week. I plan to start checking for parasitic draw soon, but I'm gonna need to get a new ammeter since mine doesn't want to read for some reason. It's what you get for going cheap I guess.

Thanks for the help.
87PontiacFGT NOV 20, 10:33 PM

quote
Originally posted by theogre:

any Charger needs 13.5-14.7 DC volts. No AC volts.
Most "dump" "dumb" chargers just has transformer & rectifier & optionally a meter. Little or nothing to smooth out the DC like capacitors because of batteries don't need it.
"Smart" chargers add "logic" like won't charge a "dead" battery < ~ 11-11.5 volts that can cause dangerous problems.

New battery won't last long because ECM etc uses some power 24/7 & will kill it after days to a couple weeks deepening on battery type etc. You might charge it after but damage is done & never work @ 100%.



After getting the battery up to around 12.5v outside the car, the car now starts without much issue.
I assume what you're saying that since the charger, despite having a "crank" setting, probably messed with the electronics since it lacks the components necessary to smooth out the AC current well enough. Makes sense I guess. Should I be checking for any specific ECM codes?
The ECM and other components killing a battery in only a few weeks seems kinda short, since the "normal" range of draw, is around 30-50 milliamps on most vehicles.
Vintage-Nut NOV 21, 09:40 AM

quote
87PontiacFGT:
I don't suspect the alternator to be the problem, since the battery usually dies after the vehicle sits for over a week.




quote
I still suggest checking the generator/alternator output....



To me, I would want to know and it is easy to check with a voltmeter....

With the engine running, measure the generator/alternator output at the battery at idle and ~2k RPM. Then place a load on the alternator by turning on the headlights.

Normally you want to see 13.5 to 14.5 volts. Lower voltage isn't charging the battery / Higher voltage will 'cook' the battery.

BTW: IF the engine/trunk deck is open and the parking brake is 'Off', current will flow even though the ignition is 'Off" which will drain the battery fast.....