Low charge rate problem
02-27-2015, 01:45 AM
#17
Three Wheelin'
If the alternator itself is OK, check voltage drops on both the power and ground side, and you will find your answer. Ohm's law does not lie!
Age has taken its toll on some 944 electrical components, but even newer Porsches can have electrical issues that lead to slow cranking or low charging voltage. Adding voltage to a high resistance circuit will force more current through and things will act like normal (though they may get very hot!).
A common issue on later 996 and early 997 cars have is a bad crimp connection in the alternator to starter cable harness that can cause a 0.5-1.0+V drop between the alternator and starter. Fully charging or jump starting at the battery or remote jump start posts in the engine compartment would mask this issue.
First and second gen Cayennes have failure-prone starter motors that live underneath the intake manifold. When they fail (either naturally or due to coolant intrusion from leaking pipes), the starter motor draws a LOT of current (over 400 amps) and the engine cranks slowly. Jump starting the battery at the remote jumping posts under the hood (the main battery lives under the driver's seat) adds voltage to the circuit nearer to the starter motor and the engine will crank more quickly, leading to the conclusion that the battery must be at fault. I recently had to spend a lot of time convincing a customer with a Cayenne that his slow cranking issue was not his nearly new battery but the starter.
I am NOT saying that your issue is with a starter or cable harness, but I am trying to illustrate the importance of Ohm's law and voltage drop testing at every point on the power and ground side of the circuit. This will reveal the cause of your issue!
02-27-2015, 02:49 AM
#18
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Good advice Chris, although i did read this after putting it all back in.
So i cleaned all contact points.
i also installed a 2nd hand bosch battery which is a little larger than what i have now. i just had it laying around. fits into the spot and uses factory mounting.
cranked over nice and strong. turned it on and off around 10 times. no loss in power.
For the first time my battery light comes on when i turn the key on to acc.
lets hope it goes well.
So i cleaned all contact points.
i also installed a 2nd hand bosch battery which is a little larger than what i have now. i just had it laying around. fits into the spot and uses factory mounting.
cranked over nice and strong. turned it on and off around 10 times. no loss in power.
For the first time my battery light comes on when i turn the key on to acc.
lets hope it goes well.
02-27-2015, 09:02 AM
#19
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slowly getting there.
Battery is staying charged. after driving ect. But for some reason. the starter motor struggles to crank the motor over some times.
It'll click and hum. like a nearly dead battery. But if i give it a little bump in 1st or reverse while holding the key in the crank position then dropping the clutch, it'll crank over like the battery is full.
Will be looking at starter wire issues.
Battery is staying charged. after driving ect. But for some reason. the starter motor struggles to crank the motor over some times.
It'll click and hum. like a nearly dead battery. But if i give it a little bump in 1st or reverse while holding the key in the crank position then dropping the clutch, it'll crank over like the battery is full.
Will be looking at starter wire issues.
02-27-2015, 02:25 PM
#20
Thanks for posting this info. I'm in the market for a canyenne within the year.
Paulyy have you thought about just building a new set of wires. pretty cheap and easy to do.
Paulyy have you thought about just building a new set of wires. pretty cheap and easy to do.
So, you are saying that your battery is discharging due to the low charging voltage situation and it cranks slowly sometimes?
If the alternator itself is OK, check voltage drops on both the power and ground side, and you will find your answer. Ohm's law does not lie!
Age has taken its toll on some 944 electrical components, but even newer Porsches can have electrical issues that lead to slow cranking or low charging voltage. Adding voltage to a high resistance circuit will force more current through and things will act like normal (though they may get very hot!).
A common issue on later 996 and early 997 cars have is a bad crimp connection in the alternator to starter cable harness that can cause a 0.5-1.0+V drop between the alternator and starter. Fully charging or jump starting at the battery or remote jump start posts in the engine compartment would mask this issue.
First and second gen Cayennes have failure-prone starter motors that live underneath the intake manifold. When they fail (either naturally or due to coolant intrusion from leaking pipes), the starter motor draws a LOT of current (over 400 amps) and the engine cranks slowly. Jump starting the battery at the remote jumping posts under the hood (the main battery lives under the driver's seat) adds voltage to the circuit nearer to the starter motor and the engine will crank more quickly, leading to the conclusion that the battery must be at fault. I recently had to spend a lot of time convincing a customer with a Cayenne that his slow cranking issue was not his nearly new battery but the starter.
I am NOT saying that your issue is with a starter or cable harness, but I am trying to illustrate the importance of Ohm's law and voltage drop testing at every point on the power and ground side of the circuit. This will reveal the cause of your issue!
If the alternator itself is OK, check voltage drops on both the power and ground side, and you will find your answer. Ohm's law does not lie!
Age has taken its toll on some 944 electrical components, but even newer Porsches can have electrical issues that lead to slow cranking or low charging voltage. Adding voltage to a high resistance circuit will force more current through and things will act like normal (though they may get very hot!).
A common issue on later 996 and early 997 cars have is a bad crimp connection in the alternator to starter cable harness that can cause a 0.5-1.0+V drop between the alternator and starter. Fully charging or jump starting at the battery or remote jump start posts in the engine compartment would mask this issue.
First and second gen Cayennes have failure-prone starter motors that live underneath the intake manifold. When they fail (either naturally or due to coolant intrusion from leaking pipes), the starter motor draws a LOT of current (over 400 amps) and the engine cranks slowly. Jump starting the battery at the remote jumping posts under the hood (the main battery lives under the driver's seat) adds voltage to the circuit nearer to the starter motor and the engine will crank more quickly, leading to the conclusion that the battery must be at fault. I recently had to spend a lot of time convincing a customer with a Cayenne that his slow cranking issue was not his nearly new battery but the starter.
I am NOT saying that your issue is with a starter or cable harness, but I am trying to illustrate the importance of Ohm's law and voltage drop testing at every point on the power and ground side of the circuit. This will reveal the cause of your issue!
02-27-2015, 04:27 PM
#21
slowly getting there.
Battery is staying charged. after driving ect. But for some reason. the starter motor struggles to crank the motor over some times.
It'll click and hum. like a nearly dead battery. But if i give it a little bump in 1st or reverse while holding the key in the crank position then dropping the clutch, it'll crank over like the battery is full.
Will be looking at starter wire issues.
Battery is staying charged. after driving ect. But for some reason. the starter motor struggles to crank the motor over some times.
It'll click and hum. like a nearly dead battery. But if i give it a little bump in 1st or reverse while holding the key in the crank position then dropping the clutch, it'll crank over like the battery is full.
Will be looking at starter wire issues.
I wonder if you've just got a bad spot in the starter? Or something really odd, like the starter is binding against the FW (like the FW is out of round, or there's some gunk or something on the teeth?), and once you roll it just a smidge, it's enough to crank?
I wouldn't expect crappy wiring to magically fix itself just because the motor rocked slightly.... :/
02-27-2015, 08:18 PM
#22
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I wouldn't expect crappy wiring to magically fix itself just because the motor rocked slightly.... :/
Sometimes it wouldn't start, but would bump start instantly. Most times it started fine. Everything checked out perfect which was no surprise, as it was all new.
It turned out the ground cable was broken about a foot down inside the insulation, and would make contact or not depending on how the engine shook when it was shut down. Strangely it had zero effect on running, so it was a bitch to diagnose.
02-27-2015, 08:27 PM
#23
A long long time ago I had a Ford Falcon Sprint with a Boss 302 stuffed in it (I miss that car...)
Sometimes it wouldn't start, but would bump start instantly. Most times it started fine. Everything checked out perfect which was no surprise, as it was all new.
It turned out the ground cable was broken about a foot down inside the insulation, and would make contact or not depending on how the engine shook when it was shut down. Strangely it had zero effect on running, so it was a bitch to diagnose.
Sometimes it wouldn't start, but would bump start instantly. Most times it started fine. Everything checked out perfect which was no surprise, as it was all new.
It turned out the ground cable was broken about a foot down inside the insulation, and would make contact or not depending on how the engine shook when it was shut down. Strangely it had zero effect on running, so it was a bitch to diagnose.
I would have been chasing my tail a lot on that one. Then again I seem to do that a lot LOL....
"It can't POSSIBLY be this..." - famous last words spoken in the Omni garage