Not so sure on the starter draining the battery but a bad diode in the alternator can drain the battery. The bad diode can cause the circuit to charge even with the engine off, draining the battery.
Can an alternator be bad if it is charging correctly ?
YES
Can a starter draw so much power that it drains a battery just by sitting?
Normally no, starters don't draw any power unless it's cranking... There is no power passing through the wire that triggers the solenoid... But there is a big battery wire supplying power that in theory could drain the battery, But I've never seen one do it...
Yeah, the battery is in the trunk. The positive cable runs to a Ford solenoid then across the axle hump and to the left side. Inside, it runs along the left rocker inside and up through the firewall to the starter. It isn't exposed to the elements except in the engine bay.Trunk mount Battery? Have you checked your cables?
Do not discount the starter motor.This wasn't the problem.
The problem persists. With a battery over 12.6 volts, the car spins over. Below 12.4, it drags like there is 20 to 1 compression!
I put the starter in in 2008. When the engine is cold, the starter doesn't spin that fast. When the engine is warm, it seems to spin faster. When the engine has been run awhile, it turns over slower but still enough to start. It never seems to crank over fast like I have heard other big block cars with the Denso mini starter. I am wondering if this starter is a contributing factor.
Last time I was going around with this problem, I found the map light to be A problem. It obviously is not THE problem.
I did not disconnect the alternator. It is charging. The voltage at the relay and battery is higher with the engine running. Can an alternator be bad if it is charging correctly ? Can a starter draw so much power that it drains a battery just by sitting? That makes no sense to me but who the heck knows. I have another new mini starter here to try. It requires unbolting and moving the header so I'd rather save that task for later if I can.
I am going back to square one tomorrow. Pulling the alternator wire, fuses and who knows what else. I have been intending on correcting a few errors with the wiring anyway. When I changed to these aftermarket gauges, some of the lighting wires got grouped together and connected to the wrong power feed. The trunk light only comes on with the key ON. The radio won't hold a memory.
Lots to do !
Maybe last time I quit looking too early and didn't
Are you running a factory style gear-reduction starter motor? This will make the car sound more sluggish than others if they are running a direct-drive (1:1 ratio) starter motor. And the fact that you have the battery in the trunk, probably accounts for at least 1 Volt of loss at the starter under cranking conditions....and remember you are lucky to see 9 Volts at the starter under cranking conditions.Thank you.
I have heard other Mopars with high performance engines and they seem to crank over much faster than I do. It has almost always been this way with this car. When the engine has been warmed up, it fires up quickly...The starter spins pretty fast and the engine fires up right away. I run a 10w40 oil so it isn't as if I'm trying to crank over a cold engine on 60 weight Harley Davidson oil!
This is interesting! My 94 GT Mustang does the same thing. As I was reading previous posts I said, "it sounds like my Mustang problem" unfortunately I have not been able to fix that either. But I would consider the Ford solenoid??Yeah, the battery is in the trunk. The positive cable runs to a Ford solenoid then across the axle hump and to the left side. Inside, it runs along the left rocker inside and up through the firewall to the starter. It isn't exposed to the elements except in the engine bay.
I did check the voltage reading at the starter relay and the number is almost the same as the battery. It is hard to test the alternator stud for voltage with the car running since it is so close to # 2 header tube.
Yeah, the battery is in the trunk. The positive cable runs to a Ford solenoid then across the axle hump and to the left side. Inside, it runs along the left rocker inside and up through the firewall to the starter. It isn't exposed to the elements except in the engine bay.
I did check the voltage reading at the starter relay and the number is almost the same as the battery. It is hard to test the alternator stud for voltage with the car running since it is so close to # 2 header tube.
Good idea.
I just went out to check on it. To charge this AGM battery, I have to use a conventional battery as a go-between.
First, I disconnected the negative cables from the battery and bridged them to the post with the test light. There is no spark and the bulb does not light up.
I connected the cables and checked voltage. Sometimes these AGMs charge to 13 volts or slightly over, sometimes the charging unit shuts off in the 12.6 range. This time it was at 12.5. The car would barely turn over. I used jumper cables to the other battery and it spun over fine, actually faster than usual. Is it the AGM battery to blame?
No. I disconnected the cables from the AGM and connected jumper cables directly from the good battery. The starter spun over just as slow as it did with the AGM battery alone.
In short, neither battery on its own can adequately spin the engine over despite having adequate voltage. The batteries together work just fine. I do suspect the starter now or at least the connections at the starter.