safulop

I've noticed for some months that my S4 starter sort of struggles to get the first turn done, then the cranking speed is good and start-up sequence completes normally. With the arrival of chilly weather here in Fresno (down near freezing overnight) the morning start is getting a bit interesting. That first turn from the starter almost seems like it won't make it all the way around, and then she does and everything goes fine after that. When the car is warm the problem is hardly noticeable, there is maybe a slightly slower first crank. The car runs perfectly, cold or warm. Engine oil is 5W40, some fancy synthetic (AMSoil I think).

Is this just a soft battery? I thought I had a fairly new battery with this car.

-Sean

Dave928S

It'd be worth going to an auto electrician or battery supplier and get them to do a high discharge test. That'll tell whether the battery is on the way out or not. Cold weather can often accelerate the death of a battery.

Nicole

First thing I would do is clean the contact surfaces on the ground strip from battery to trunk. I have experienced corrosion in that area, and have seen 928s fail to start because of it.

There is another ground strap from the right front frame rail to the engine. It's kind of hidden from view until you get under the car with the belly pan off.

I don't remember what the ground looks like at the starter itself, but that might be another place to check.

This is all assuming that your battery is still good.

Dave928S

+1 on what Nicole said .. bad grounds can also be the reason a battery fades away in the first place, because of poor charging.

T_MaX

Water in a cylinder(s)?

WallyP

As above - most likely cause is dirty main battery connections. Poor connection, then the high current draw "burns thru" the crud and you get a better connection for a short time.

Less likely, but it can also be a broken connector inside the battery, which can be really bad news if it causes the battery to explode.

Also possible, but less likely, is a worn starter.

17prospective buyer

Could be within the starter itself. Starters generally develop high torque and demand the highest amperage when the field windings and armature are first energized. I would do all the simple things first. Clean all ground points and terminals on the starter. Check the starter circuit wires for corrosion/voltage drops.

You can't diagnose a starter circuit properly without a fully charged good condition battery though, so make sure it's up to scratch.

Lizard928

Grounds then starter in that order.

safulop

OK thanks, this gives a track to run on at least. I never thought of the grounds for this issue, but I have seen loose battery connections cause all sorts of problems and shops frequently overlook it and want to replace the alternator.

-Sean

T_MaX

Lets us know what you find or don't find.

safulop

OK, well, this problem was apparently caused by this problem:

https://rennlist.com/forums/928-foru...smog-pump.html

The old smog pump bearing was so hard to turn, it was disturbing the ability of the starter to crank the engine.

kelanel

if ground points are ruled out, it might be due to ground strap corrosion underneath the jacket. is the ground strap original? Voltometer might read lower as a symptom. You could use jumper cables to bypass the strap and see if that provides a positive change.

safulop

Read my latest post, it is not an electrical problem.

Speedtoys

safulop

Yeah well, on the other hand my voltmeter has always read too low, can't figure out why. My mechanic suggested it is caused by the main "kill switch" that was installed in the rear, the ground now has to travel through a switch. We'll see how it does when the colder weather arrives.

-Sean