Starter turns over very slow but battery is full

[Jeff5678]

I have an 87 911 cab and the latest problem is the starter turns over slowly. I tested the battery and it is full, it is also new, and the alternator is putting out 14.5 volts at idle. If the car sits for a week the battery goes down to about 9.6 volts and the starter will not turn over at all. I have cleaned the battery terminals and put a small amount of grease on them for better contact...that did not help. I am not thrilled about trying to get to the starter but I think I will have to. Any tips on how to get to the starter? It looks like a major ordeal. Any help would be appreciated.
Thanks,
Jeff

[dicklague]

You need to do a load test on the battery. I had the same thing happen to my 1973 with two batteries up front. I would leave it for a few days and it did not have the power to start up. I could put a charge on then and they would last a few days.

So I took out my trusty Harbor Freight battery tester and on battery would go from 12.5 to 8 volts in 30 to 40 second. The other would drop to about 12. I disconnected the bad battery and am running on 1 battery which you can do on these cars because they are wired in parallel.

So get the battery load tested. I bet the battery is your problem because my alternator was putting out 14 vdc.

Batteries are quite finicky and fragile. can last 4 years or 4 months.

that Harbor Freight tester is one of the best test tools I have....great $20.00 investment.

[dicklague]

Be sure the battery is thoroughly tested before messing with anything else. Load test is vital

[rfuerst911sc]

In my opinion if after only one week your voltage is that low you have something pulling current when it should not. You need to figure out if that is the case. If I am right you have to correct that condition. Once that is fixed you need to fully charge your battery and monitor how well it works over a few days or so. If it still turns over poorly it still may not be the starter. Could be as simple as a bad ground. Or an ignition switch or possible other items including the starter/solenoid.

[crustychief]

+1 on the load test.

[dicklague]

You don't know anything until you do the load test, Charge the battery up with a good charger for a few hours and then see it passes a load test. I have found the battery is the most unreliable part of the system. Too many people spend too much time and $ replacing other components and then find out it was the battery after all.

When you say the battery is full, do you mean the water? My bad battery was full on water, but would not hold a charge.

[Jeff5678]

When I said full I meant a full charge. I will do the load test this weekend and see what i find. The battery is a race battery and it is only abnout 6 months old. I always keep it on a battery minder when it will sit for more then a few days.