Help, Won't turn over

jasonq · 11-07-2003, 10:38 AM

I have searched for starting problems, but haven't found anything that fits, so here's my problem.

73.5 911T 2.4 CIS, motor run really well.

usually, the first time i start the motor each day it turns over strongly, and takes 1-5 seconds to catch. the rest of the day, it starts instantly. same behavior at temps from 40-90 degrees.

I usually drive the car about once every 2-3 days.

Twice, once on a hotter day (about 85) in september and once this morning (about 40 degrees) the motor would not turn over. I last drove the car on the day before yesterday.

I turn the key, the motor turns sometimes, but only like 1/2 turn, then stops. When trying, It looks like voltage drops to nothing because the clock in my cd player resets. this may simply be due to the fact that current is flowing thru a stationary starter motor.

the batteries are not dead, head lights come on strong as long as i am not trying to start it (i turn them off while trying to start). But They may be weak, and not able to source enough current for the starter.

I had to get to work, so i drove my car from that other flat engine brand.

when i get home, if it is still happening, i'll use jumper cables to the subaru to make sure it is not the batteries. I'll also put a mulimeter in the cigarette lighter to see what the voltage is doing.

Last time it happened, after a 30 minute wait (walk to phone, wait for girlfriend to drive to parking lot with cables) i jumped it, and it turned over, but didn't catch. Towed to my wrench, where later that day, it started fine, no trouble found. the delays may have played a part.

batteries? starter? your idea here? what else should i do/check?

at least this time it is in the garage,
thanks,
jason

911pcars · 11-07-2003, 11:21 AM

Sounds like a borderline battery. It also could be something like dirty or loose connections or perhaps a circuit discharging it between use.

I'd check the battery connections and the ground strap on the gearbox mount. Trickle charge the battery overnight, then have it checked out at your local electrical shop. BTW, many shops now have state-of-the-art testers that can test a discharged battery to see if it's merely discharged or terminally ill.

There's also a chance the alternator isn't helping, but check the battery first. Once the car is running, connect a voltmeter up to the battery posts and monitor the charging rate at idle and off idle; should be between 13.5 and 14.5 volts. If everthing thus far is okay, check for parasitic. Get back to us if you have ventured this far.

Sherwood
http://members.rennlist.org/911pcars

rickeolis · 11-07-2003, 11:42 AM

"I had to get to work, so i drove my car from that other flat engine brand."
This means Ferrari, Subaru, VW, Corvair?

I would suspect corroded cabling and ground straps issues, because of when you said that the lights are bright. This makes me think that under a light amperage load things are fine, but under a heavy load they suffer, that really sounds like cabling issues to me. Good luck.

BTW- Does a jump start work well?

jasonq · 11-09-2003, 03:15 PM

Finally had time to my problem diagnose futher:

battery voltage, no load =12.25
wiith lights on=11.50

this made me think weak/dead batteries

all connections are tight and no coorosion, including the transmission ground strap.

jumped started off the subaru with the twin batteries still in, started straight off. once again i'm thinking dead batteries.

take batteries to tire/brake/battery place, they test, say dead but otherwise appear fine.

I charge both batteries, check specific gravity, all chambers are marginal. could use some more sulfuric acid. the batteries could use some maintaince, but are probably ok for now, but might not last so long. btw batteries are 2x interstate 911-50 or something close to that that are 4.5 years old.

with no batteries in the car, i try to jump start off the subaru battery. will not turn over again. try off an exploder, won't turn over. Install both freshly charged batteries, and it turns over and starts up.

So i guess alone niether the subaru or explorer batteries had enough amps to even turn over the motor. that seems odd to me, making me think again that while the batteries were dead, maybe the starter isn't in such good shape either.

Ok, now car is running, at idle (1500 rpm with throttle lever, car is cold, any lower and it won't hold steady). Voltage = 12.75. So that makes me think the reason for the dead batteries is a ailing alternator.

Remeber something about an alternator and the PO, i go look at the records. 1.25 years ago, our wrench installed a new alternator and voltage regulator. Doesn't seem like they should go bad so fast (5k miles). here are the part numbers installed. This mechnic is pretty good, i don't have any reason to believe he would do something stupid.

alternator=p# PMX 13025
VR=P# 91160320613 marchal 55W

So summing up, i think:
my batteries not the root of the problem, but probably should be replaced (leaning toward single odyssey)

my starter must take serious juice to turn over. This too is probably no the root of the problem, but replacing might not be a bad idea. (i just always have had a bad feeling about it, but no reason why)

my alternator seems to be weak, but could one die so fast? I'll call the wrench tomarrow about this, maybe its still covered by a parts warrantee.

What have I missed?

and how hard is it to get at the starter in a 73? I've heard semi horror stories about getting at the bolts, lower transimissions, etc. If its all that, and i decided to get one, i'll pay to have it doe. And lastly my P-car guy is about 40 miles away, but there is a pretty good air cooled VW guy about 5 miles away. I am assuming, they could do a starter no problem if i went there.

thanks muchly,
jason

jasonq · 11-09-2003, 03:26 PM

Oh yeah,
I checked the current draw when off, 5ma. sounds about what it would take to run the clock.

with the batteries out, i check the resistence between the positive lead and ground with the clock disconnected, 8 megaohms.

so basically, i don't think i have an shorts draining the batteries while parked.

later,
jason

makaio · 11-09-2003, 06:39 PM

Battery(s). Possibly one or more bad cells.

911pcars · 11-09-2003, 06:49 PM

Jason,
As you discovered, the batteries won't charge properly when the charging system is only putting out 12.75 volts. Try putting a load on the system while monitoring the charge voltage (highbeams, A/C fan, rear window defroster, etc.). If the charging system is okay, the alternator output should compensate for the added current draw of these accessories.

Don't condemn the batteries until they show they can't hold a charge.

Sherwood

jasonq · 11-09-2003, 07:14 PM

Sherwood,
yeah, i don't think the batteries are to blame, i think they may need some maintaince. I am only really considering replaceing them they are showing their age, but as far as i can tell they are ok now, and still functional. I don't think they are not holding change, since i have let the car sit for a week two weeks ago, and it started no problem.

I also tried one more thing. Car at idle, removed the ground straps from the batteries. the alternator should put out enough power to both run the engine and charge the batteries, so i figured the car should keep running since the load was lightened by not having to charge. Nope, stalled right away. one more piece of evidence that the alternator is weak.

I once had a 72 toyota with no battery at all that ran fine, once it push started it...stalling in traffic just wasn't an option.

I think the problem is the charging system. I'll try looking at the voltage to the batteries at idle with headlights on/off etc, but at this point i'm pretty sure its the charging system.

I'll call my mechanic tomarrow, see what he thinks.

thanks,
jason

rickeolis · 11-10-2003, 08:57 AM

As far as the starter goes, you don't need to worry too much, it is easier than you think. I can take my '69 starter off in about 15 minutes.

All I have to do is have the car jacked up, with stands, and undo the battery first. Then while under the car reach one arm around the tranny for the top bolt, it looks harder than it is, the lower bolt is very easy, then you're done!

Good luck-

Rot 911 · 11-10-2003, 09:02 AM

have you tried something as simple as putting the battery from one of your other cars temporarily into the 911 and see if it starts. sounds to me like you have two failing batteries.

jasonq · 11-10-2003, 09:43 AM

Kurt,
while i did not actually put another battery in the car, while the batteries were out, i did use jumper cables to the batteries in my subaru (cheap exide, but starts the subaru no problem), would not turn over. Same thing with a battery in an explorer.

two freshly charged interstate u911-50 (2x 300 cca i think), and it turns over and starts.

Seems like the starter should be able to at least turn over on a single ~400 cca battery. Thats why i think the starter is suspect, but not the core of the problem. Then again, there was probably a reason they put 2 batteries in the car, so maybe the starter really does need all that juice???

thanks for the interest,
jason

Rot 911 · 11-10-2003, 09:48 AM

The two batteries were for weight equalization not more power. Unless you are in the concourse crowd most everyone just switches to using one battery. Using jumper cables is definitely not the same as swapping batteries. Why not try a battery swap before you convince yourself it is the starter? Not much work to do and definitely cheaper in the long run.

911pcars · 11-10-2003, 10:38 AM

Kurt V,
If Porsche just wanted ballest, I'd think some lead weight would have sufficed (in fact, they did in the first 911s). However, two wimpy batteries in parallel is better than one wimpy battery, that's why they put two in there (as well as for the ballest). I believe the rating of a single OEM battery is about 350 CCA. A single Optima, for example, is 750 CCAs. Later 911s use a single larger battery.

In general, it's cheaper (and better) to check out the entire system (charging and cranking) and pinpoint the source of the malfunction than to just start replacing parts, but since this is your car, you can replace any part whether you need to or not.

MHO,
Sherwood

Rot 911 · 11-10-2003, 04:55 PM

Quote:

Originally posted by 911pcars
Kurt V,
If Porsche just wanted ballest, I'd think some lead weight would have sufficed (in fact, they did in the first 911s).

From the Porsche 911 Redbook: In 1969 "The single 45 amp battery was replaced by twin 12 volt 35 amp batteries mounted in each fender before the front wheels.This was to increase handling balance."

In any event I would still swap out a good battery out of your other car just to see if it will start the car before I started spending money.

RoninLB · 11-10-2003, 05:19 PM

4.5 year old batteries are a problem waiting to happen

dis-connecting battery from a running engine is a problem waiting to happen

a current draw test of the starter while cranking is easy. the magnetic field current meters are cheap.

911pcars · 11-10-2003, 05:56 PM

Ron,
I've been living on borrowed time with an Optima since '96. Should I have jettisoned this in '00? IMO, the time to buy another battery is when the old one wears out. On a wet cell battery, you can monitor its general condition by taking specific gravity readings of each cell every so often. On a dry cell battery, an electric shop can perform a load test.

I concur. Disconnecting the battery from a running charging system is likely to fry something unless the charging system is not working well anyway.

Porsche went to twin batteries AND removed the lead weights. I'm pretty sure they never used both.

Sherwood

RoninLB · 11-10-2003, 07:45 PM

Quote:

Originally posted by 911pcars
Ron,
I've been living on borrowed time with an Optima since '96.

IMO, the time to buy another battery is when the old one wears out.

Disconnecting the battery from a running charging system is likely to fry something

Hi Sherwood
the optima doesn't take the routine battery crash as a wet one from a freezing out door start to my experience so far. Yeah you could monitor the condition. I bet your car is in great shape. But the routine is if it starts the car it's OK

I believe a diode could blow from the surge. I wonder about the internal regulators also blowing? I've never read nor heard anything about that?
anyway.......Ron

jasonq · 11-14-2003, 08:46 PM

Resolution:
took to wrench for charging system testing.

voltage at batteries when running was low because....corroded leads, but it was tricky to find. The corrosion was not at the battery connections, but inside the insulation. Water had seeped inside the jacketing near the battery and corroded the wires. It was not visible from without some digging. He says he has seen this before.

this keep the batteries from both fully charging and supplying full current to the starter.

only time will tell if the problem resurfaces...

thanks to all,
jason

911pcars · 11-14-2003, 10:37 PM

Jason,
Glad to hear you now have more $$ to spend on other parts of the pcar.

I believe many good batteries get replaced with a new one merely because it needed/wasn't getting a full charge due to bad connections, or just left the lights on.

I commend the tech who correctly diagnosed this for you. Many techs are, unfortunately, really good parts exchangers/salesmen.

Sherwood