rickjaffe

I've been having some problems starting my S4,. Car has 94k miles. I've replaced the battery in January. I know I have a small draw on the current beyond what's acceptable (.83-84 mv which is more than the .5) Haven't troubleshot that yet, but because of that I keep the car on a trickle charger. Battery tender shows green when I disconnect and drive a few miles, then after I do an errand, the car won't start. some of the electronics come on but starter won't even engage, not even a clicking noise. I can't believe that driving 1.8 to 3.3 miles during the day w/o a/c (meaning not a big load) can fully discharge a bettery even if the alternator isn't working. Amy I incorrect about that?
It feels to me like the starter isn't engaging at all sometimes.
but I have conflicting data points or symptoms.
on the one hand, both times when it wouldn't start at a remote location, when I charged it with a car via cables, after 5 minutes or so, the car started immediately. That would weigh towards the battery discharging below what is necessary to even engage the starter.
fyi: I had the battery tested at autozone and it checks excellent in terms of cranking and storage.
conflicting data point pointing away from alternator: at home, even at full charge, it wouldn't start.

Had a similar issue with an 66 Lincoln. I changed out the cable between the starter and starter relay and changed the starter relay and that solved the problem.

does a Porsche have something similar? is it a relay in the fuse box and can it be intermittent as opposed to just working or not working. I don't know much about modern cars.

I'll check the alternator as well, but I don't think that's my main problem; for now seems like starter is intermittently not engaging.

I haven't tried jiggling the shifter in park. maybe it's not doing what it has to do to send info (close some circuit) that car is in park?

any ideas?

thx

SteveG

Well, it sounds like an intermittent ground, relay (fuel pump?), or injector wire. There is a diagram in the New Visitor thread of ground points to clean [post 33]. Some do this annually, depends on climate and storage conditions. The batt ground strap can have corrosion under the insulation and still look fine. If it is original I would replace it simply b/c it is not expensive. A batt can have a weak cell and not show unless it is load tested. These are the simpler, cheaper things I would start with.

Mrmerlin

As Steve suggested look at the battery connections ,
clean every connection in the battery well and the ground strap connection,
replace the ground strap if its original.

To see if you need a new starter relay open the hood remove the hot post cover.
then separate the 14 pin connector ,
with the top half touch the pin the furthest to the front and closest to the right fender to the hot post,
NOTE this is pin 14 in the top half of the connector the thick yellow wire.
the starter will run.
NOTE This will remove the ignition switch and the starter relay from the starter circuit.
NOTE make sure the trans is in park or in neutral and the E brake is on.

NOTE to start the engine,
turn on the key to run,
then touch the pin 14 to the hot post the engine will crank and start

NOTE you can damage the relays by trying to start the engine with a low charged battery,
the relays will not get a sufficient signal to close and start arcing at the contacts,
once the buildup is enough then the relay may close but the contact points will not pass current.

Taguid

There
is also a large ground strap from frame to engine under passenger side. Make sure it is clean and not corroded or broken and while you under check starter connections like the yellow one Stan referred to and the large red power from the battery.

rickjaffe

thanks, will check the battery ground first. so no starter rellay I can replace after I check the battery ground? a relay would seem the next logical step since I feel it's not engaging, unless a high amoung to juice is pumped into the battery and sometimes not even then.
but battery cable and surrounding area first and will clean with a wire brush and wd 40 I guess, right?

Mrmerlin

do you have to ask?

Deoxit my man.
Deoxit !

SteveG

I edited my first post to add "post 33" of New Visitor thread, to make it clear for all, called "engine ground strap" in the pic, that is not necessarily the culprit, but definitely something to clean. WD40 is a good general cleaning agent; it does leave a residue, but DeOxit is way better for electrical corrosion. Tools to have are small wire brushes and emery paper. This car is finicky about voltages especially for the ignition at start-up. Green corrosion on coil wires and grounds, and connections to distributors seem to attract moisture, which will give intermittent no-start, also sluggish, no-accel at cruise.

Farland

Sounds like a similar issue I had with one of my motorcycles. I went through 2 batteries in about 2 years. Success at cranking seemed to go from reliable to intermittent in about 6 months of having each battery and there seemed to be no rhyme or reason to anything. To make things worse, battery charger was showing fully charged each time before riding.

After griping about the problem to a friend, he gave me a lithium-ion battery to try out. I installed and was riding for five minutes on the highway before bike just turned off. I was not able to start the bike up after that and had to tow to the mechanic. When he tore everything down, we came to discover the problem all along was intermittent ground. It appears the higher voltage from the lithium-ion battery put just enough pressure to finish off whatever was left of the ground connection.