Slow Cranking, full power to everythiong else

need RX7 · 01-01-2009, 09:19 PM

I went out and tried to start my car last night, it cranked very slow. I put it on a charger for about 4 hours, let it sit overnight and tried starting again today. It still cranked slowly today, but I tested the headlights and they pop right up and shine bright. As soon as I try starting it, all the lights dim and the voltmeter needle plunges.

Any ideas what could be wrong. The starter was replaced in February. I'm thinking about the wires running from the battery to the starter, what should I look for when I'm looking at them? Any other ideas?

RotaryProphet · 01-01-2009, 09:44 PM

Sounds like the engine ground, or possibly corrosion or loose battery terminals or the starter positive line.

rx7 FC TII · 01-01-2009, 10:48 PM

im having this problem along with the 3rd gen that i hang out with. i havent started to work on it and figure it out yet but if i figure it out ill report back.

EDIT: ive done a bit more research on this and its sounding like its most likely the starter.check all the connections and grounds for it and if not then you can try to replace the brushes on the starter if you go to napa and order them. ill be doing it this weekend so ill let you know.

http://www.napaonline.com/MasterPage...=Starter+Brush

RETed · 01-02-2009, 12:09 AM

Sounds like a bad battery...

What is the voltage with everything off?
Ideally it should be over 13.0VDC.
What is the voltage while cranking?
Ideally it should be over 10.0VDC.

The engine can crank down to 9.x VDC, but if it gets any lower than that, the battery is no good.

-Ted

need RX7 · 01-02-2009, 03:06 AM

It sits right at 12v with the key turned to on and the parking/dash lights on (I couldn't see anything without them ha) I walked away for a couple minutes (with the parking lights on) and it had dropped to about 11v. So I guess I'm off to get a new battery...

I'll still check out the grounds and stuff just in case... Thanks for the help guys.

RotaryProphet · 01-02-2009, 09:33 AM

12 volts is normal for a battery on a non-running engine. 13.5 is about where you want the voltage in a running car with the alternator working.

djmtsu · 01-02-2009, 11:44 AM

Forget about voltage when the battery is idle (no high amp draw).

Check the voltage with a GOOD METER (no dashboard gauge) when you are cranking the car.

The battery might have a 'dead cell'. They can show a normal voltage when idle, but when load is applied the voltage drops significantly.

I used to be a DC power technician, so I have a clue.

need RX7 · 01-02-2009, 02:46 PM

Alright, the battery's at Murray's right now getting tested. Whether or not the battery is the problem, I think it's about time for a new one anyway. It's not even the right one for the car, it's effing huge.

Hopefully I can get an Optima.

Whizbang · 01-02-2009, 02:51 PM

dont be so sure about the too huge. The rx7s (FB and FCs) usually speced D28 batteries

need RX7 · 01-02-2009, 03:00 PM

Quote:

Originally Posted by Low Impedance

dont be so sure about the too huge. The rx7s (FB and FCs) usually speced D28 batteries

Yeah, I know the battery's supposed to be pretty big, but this one doesn't even fit right in the battery tray (and the PO told me it came from a truck

)

Fidelity101 · 01-02-2009, 03:59 PM

optima red/yellow top are good batteries but pretty damn heavy and since their solid state if you leave your lights on or something overnight and you drain your battery, tough luck you need another one.

djmtsu · 01-02-2009, 04:27 PM

Quote:

Originally Posted by Fidelity101

optima red/yellow top are good batteries but pretty damn heavy and since their solid state if you leave your lights on or something overnight and you drain your battery, tough luck you need another one.

Not solid state, Absorbed Glass Mat.

And yes, once they are toast, they don't come back. I recently had my Red Top go down, form lack of driving. It charged back up, but only lasted another 2 months before it died all together. Now I have the 1000 CCA Red Top in it.

need RX7 · 01-02-2009, 04:33 PM

Alright, the battery I had turned out to be toast, so I picked up a DieHard from Sears. I don't want to drop $150 for an Optima on a car that I probably won't keep for much longer. I haven't hooked it up yet (need to put my trailing coil back on) But I'm pretty confident that the battery will fix the problem.

Fidelity101 · 01-03-2009, 02:03 AM

Quote:

Originally Posted by need RX7

Alright, the battery I had turned out to be toast, so I picked up a DieHard from Sears. I don't want to drop $150 for an Optima on a car that I probably won't keep for much longer. I haven't hooked it up yet (need to put my trailing coil back on) But I'm pretty confident that the battery will fix the problem.

Thats the spirit!

rx7 FC TII · 01-03-2009, 02:22 AM

i wish that was my problem. my starter is fucked. itll barely start so thats my project tomorrow.

congrats on fixin yours.

01-01-2009, 09:19 PM	#1
need RX7 Clean S4 Nutswinger Join Date: Mar 2008 Location: Sterling Heights, MI Posts: 485 Rep Power: 18	Slow Cranking, full power to everythiong else I went out and tried to start my car last night, it cranked very slow. I put it on a charger for about 4 hours, let it sit overnight and tried starting again today. It still cranked slowly today, but I tested the headlights and they pop right up and shine bright. As soon as I try starting it, all the lights dim and the voltmeter needle plunges. Any ideas what could be wrong. The starter was replaced in February. I'm thinking about the wires running from the battery to the starter, what should I look for when I'm looking at them? Any other ideas? __________________ -Ted -1986 Mazda RX7 Sport [DD/beater]: engine finally let go at 205k. parts car status. -1986 Mazda RX7 base [resto-mod project]: S5 n/a swap in progress.

01-01-2009, 10:48 PM	#3
rx7 FC TII Rotary Fanatic Join Date: Feb 2008 Location: hoover Posts: 161 Rep Power: 18	im having this problem along with the 3rd gen that i hang out with. i havent started to work on it and figure it out yet but if i figure it out ill report back. EDIT: ive done a bit more research on this and its sounding like its most likely the starter.check all the connections and grounds for it and if not then you can try to replace the brushes on the starter if you go to napa and order them. ill be doing it this weekend so ill let you know. http://www.napaonline.com/MasterPage...=Starter+Brush Last edited by rx7 FC TII; 01-01-2009 at 11:42 PM.

01-02-2009, 03:06 AM	#5
need RX7 Clean S4 Nutswinger Join Date: Mar 2008 Location: Sterling Heights, MI Posts: 485 Rep Power: 18	It sits right at 12v with the key turned to on and the parking/dash lights on (I couldn't see anything without them ha) I walked away for a couple minutes (with the parking lights on) and it had dropped to about 11v. So I guess I'm off to get a new battery... I'll still check out the grounds and stuff just in case... Thanks for the help guys. __________________ -Ted -1986 Mazda RX7 Sport [DD/beater]: engine finally let go at 205k. parts car status. -1986 Mazda RX7 base [resto-mod project]: S5 n/a swap in progress. Last edited by need RX7; 01-02-2009 at 03:09 AM.

01-02-2009, 09:33 AM	#6
RotaryProphet Rotary Fanatic Join Date: Sep 2008 Posts: 147 Rep Power: 17	12 volts is normal for a battery on a non-running engine. 13.5 is about where you want the voltage in a running car with the alternator working. Last edited by RotaryProphet; 01-02-2009 at 11:49 AM.

01-02-2009, 11:44 AM	#7
djmtsu My minds tellin' me no... Join Date: Feb 2008 Location: Murfreesboro, TN Posts: 4,043 Rep Power: 22	Forget about voltage when the battery is idle (no high amp draw). Check the voltage with a GOOD METER (no dashboard gauge) when you are cranking the car. The battery might have a 'dead cell'. They can show a normal voltage when idle, but when load is applied the voltage drops significantly. I used to be a DC power technician, so I have a clue. __________________ 1976 Mazda Cosmo RX-5 1976 Mazda Cosmo RX-5 2003 Toyota Tundra TRD 2015 Toyota 4Runner SR5

01-01-2009, 09:44 PM	#2
RotaryProphet Rotary Fanatic Join Date: Sep 2008 Posts: 147 Rep Power: 17	Sounds like the engine ground, or possibly corrosion or loose battery terminals or the starter positive line.

01-02-2009, 02:46 PM	#8
need RX7 Clean S4 Nutswinger Join Date: Mar 2008 Location: Sterling Heights, MI Posts: 485 Rep Power: 18	Alright, the battery's at Murray's right now getting tested. Whether or not the battery is the problem, I think it's about time for a new one anyway. It's not even the right one for the car, it's effing huge. Hopefully I can get an Optima. __________________ -Ted -1986 Mazda RX7 Sport [DD/beater]: engine finally let go at 205k. parts car status. -1986 Mazda RX7 base [resto-mod project]: S5 n/a swap in progress.

01-02-2009, 02:51 PM	#9
Whizbang Respecognize! Join Date: Jul 2008 Location: Δx = ħ/2Δp Posts: 3,190 Rep Power: 21	dont be so sure about the too huge. The rx7s (FB and FCs) usually speced D28 batteries __________________ For current updates and event coverage check out Follow on Twitter! @WhizbangRally Whizbang Rally's Webpage \| Facebook

01-02-2009, 03:59 PM	#11
Fidelity101 Reliable Source Join Date: Nov 2008 Location: Michigan/Illinois Posts: 336 Rep Power: 17	optima red/yellow top are good batteries but pretty damn heavy and since their solid state if you leave your lights on or something overnight and you drain your battery, tough luck you need another one. __________________ My Rx-7 Vids

01-02-2009, 04:33 PM	#13
need RX7 Clean S4 Nutswinger Join Date: Mar 2008 Location: Sterling Heights, MI Posts: 485 Rep Power: 18	Alright, the battery I had turned out to be toast, so I picked up a DieHard from Sears. I don't want to drop $150 for an Optima on a car that I probably won't keep for much longer. I haven't hooked it up yet (need to put my trailing coil back on) But I'm pretty confident that the battery will fix the problem. __________________ -Ted -1986 Mazda RX7 Sport [DD/beater]: engine finally let go at 205k. parts car status. -1986 Mazda RX7 base [resto-mod project]: S5 n/a swap in progress. Last edited by need RX7; 01-02-2009 at 04:35 PM.

01-03-2009, 02:22 AM	#15
rx7 FC TII Rotary Fanatic Join Date: Feb 2008 Location: hoover Posts: 161 Rep Power: 18	i wish that was my problem. my starter is fucked. itll barely start so thats my project tomorrow. congrats on fixin yours.