Jagtem

Car is a 2008 Cayenne S, purchased about a year ago.

The car was in great cosmetic and mechanical condition when I tested it. It started and ran flawlessly during the test drive and immediately after purchase.

The issue became apparent the next day when I went to restart the car after it had already been running/driving for a while. It just gave a half a crank and then a click and failed to start. I tried it again and it started up.

This issue got worse over several months. Basically, the car would start fine from a cold condition, but once it had been driven and brought up to temp, it would often refuse to restart on the first turn of the key. However, the car would always eventually restart. Sometimes this would require several attempts of turning the key, or waiting 5 to 10 minutes, then trying again (and again). This was particularly annoying when filling up with gas, as I'd often have to sit there for a few extra minutes trying and retrying the starter. But it would always eventually start.

I replaced the battery to no effect, and finally replaced the starter motor which seemed to completely resolve the issue. After replacing the starter, the car would start flawlessly in any condition for the next several months.

However, the issue is now returning. Again, it starts fine when cold, but now sometimes when the car is hot, it is requiring two or three attempts to start. It's not as bad as it was, but it seems like it will continue to get worse. As if the starter motor is getting weaker and weaker over time.

What could be causing this behavior? I did notice when replacing the starter that the one I removed seemed to be an aftermarket unit, so I think this may be at least the 3rd starter which has been put in the car. Is there a condition that could be causing this slow degradation of the starter motor? I'm at a bit of a loss and it's quite annoying to not be able to trust the car will start when I need it to.

Any help is appreciated.

Malibu955

The symptoms do point to a failing starter. It's possible that you got a bad replacement; pandemic parts still seem to be everywhere. Did you go with an OEM Bosch starter? If so, new or rebuilt?

Jfrahm

Voltage readings would help. I wonder if you have the dual battery setup and only replaced one battery.
It could also be a problem with the voltage regulator or alternator leading to undercharging. I had this issue with an Audi, the half-charged battery was not always capable of starting the car.
Other possible issues could be a bad battery/starter cable or cable end, poor cable to ground connection or similar.

Checking battery voltage when cold, when running and right before a hot start could tell us a lot.
-Joel.

Malibu955

Also, are you having the exact same symptoms, where you get half a crank and then a click when trying to start? Or are you getting long cranking times when hot, which can point to a failing crank position sensor and/or HPFP.

Jagtem

It's a Bosch unit. Not from the dealer, but I believe it is OEM- spec. I think it's a reman. Maybe the quality is questionable? I'm currently located in a sorta-former Balkan country (Slovenia).

Same symptoms. Half a crank, then click. Cycle the key again and it will usually fire up as normal. Again, only when engine is hot. It's happening maybe 10% of the time, but I suspect it will get worse over time. With the last starter and a hot engine, I would sometimes have to cycle the key upwards of a dozen times to finally get it to start. Super stressful when there's a line of cars behind me at the gas station.

Single battery. I'll try to get voltage readings at cold/ hot/ idle. I'm currently residing in Europe (Slovenia), so unfortunately I don't have access to my own garage and most of my tools.

I'm wondering about the possibility of a bad cable connection ground. Could a hot engine bay exacerbate such an issue? Any pointers on where to check for these cables/ connections?

Malibu955

I have a reman'd Bosch as well and it's held up great for probably 6+ years now, however people have had issues with them. Plus parts in general have had a shocking drop in quality since the pandemic, so it's very likely that your new starter is failing.



Yeah, that definitely seems like a failing starter. My Cayenne had those symptoms every once in a while prior to replacing the starter, and has never had them since. I also had an XJ Cherokee with symptoms exactly like you described (and the symptoms got progressively worse) and a new starter fixed it. So all points to the reman'd Bosch starting to fail.



Here's a diagram for all of the chassis ground locations.

theprf

Electrical connections to the starter are easy. The battery wire runs from the starter to the jump start pin. The starter is grounded to the engine, and the engine ground is below the alternator.
I don't think those are the source of the trouble, much more likely a failing starter. And they are really a joy to change.

Jagtem

Slight update to this...

The car continues to exhibit the problem of sometimes being hesitant to start when hot. Although it pretty much always starts on the second turn of the key, I suspect it will get worse over time as it did with the last starter.

I took it to my buddy who helped me install the current starter. He's an auto-electrical mechanic but does not have much experience with higher-end stuff. He was really hesitant to even consider that the rebuilt Bosch starter could be going bad. He hooked up his volt meter to the jumper posts under the hood and took a measurement with the car warmed up and at idle. The meter showed around 13.4v, which he said is far too low. He believes that the reading should ALWAYS be at least 14.5v with the car running. He believes it's definitely either the alternator or a bad ground.

I did some quick searching and it seems that the alternator output on the Cayenne can fluctuate from 13 to 14.5v depending on conditions. So his assessment of the voltage output being low may not be strictly accurate. Does this check out?

I'm also hesitant to believe it's the alternator since the car has never actually left me stranded. It always would eventually start (even if it would take several tries), which indicates to me that the battery is being charged sufficiently. It also has a new-ish battery which I replaced about 6 months ago.

Perhaps the issue is with a ground connection? Something where it gets very hot and the connection becomes less stable? I saw mention on another forum post that there was an issue with 997.1 cars that would crank slowly/ not crank when hot due to a fragile ground cable.

The last thing I'll mention is that when he gripped the ground jumper post under the hood with his fingers, it was quite hot (I felt it as well). He told me that this could be indicative of a bad ground. I have no idea if this is true, or if the post was just hot as a result of being under the hood with a hot engine.

Thanks for everyone's thoughts on this.

BobcatBrian

The voltage output from the alternator sounds fine and you really need to test at the battery. You may get a bad reading at the jump posts due to resistance and corrosion.

My money is still on the starter failing. Rebuilt starters are always hit or miss, even with Bosch.

Jfrahm

13.4 is a bit low when the battery should be recovering after a start. More interesting would be the battery voltage before trying to start. A battery load test can also tell you a lot.
The starter seems unlikely, it could be sticky to the point of taking too much current to start the engine but two starters in this condition?

Any sign of coolant loss or something like that?

oldskewel

With battery, starter, and alternator concerns here, you might consider installing a voltage logger like this, to get measurement data to look through carefully:

https://antigravitybatteries.com/pro...ker-lead-acid/

I bought one of those recently and am currently cycling it through all of my cars, noting standard measurements while everything is working fine, as a baseline for comparison later. So one day, when I'm needing to wonder how much charging voltage varies (for example) or how long it takes for the starter to get the engine started, I'll have actual info for my car while it was working well.

It's pretty simple, providing battery voltage at a 2-minute sample rate for the preceding 31 days, so you can monitor any parasitic drain, charging voltage fluctuation, starting dip, etc. Has special high sampling rate test for the starter, and also for alternator idle/high-rpm voltage.

Really happy I got it, except that looking up the URL just now for this posting, I see there is a new version out. Main benefit I see there that mine does not have is the capability for exporting data.

Newer one: https://antigravitybatteries.com/pro...tooth-tracker/

I'm completely unaffiliated with the company, other than that they are also a site sponsor here on rennlist.

IchBautAuto

100%, I put in a logger and you get all the info you would ever want and more. Mine has a display mounted on the dash so I have the battery and it's health in my face 24/7.
Before getting paranoid about parts, do a very solid battery check. These cars are manic with electrical consumption when any doors etc are open or you have minor electrical issues so it is easy to have low battery voltage without really knowing. What you really need is a resting battery voltage without opening any door. I get mine from a Ctek battery sense so if you open a door, bonnet or whatever, control modules start to operate and the battery voltage is put under load. Assuming that is good, you need to get the crank voltage. Mine is between 10 and 10.5V. Into the low 9's and systems will not function correctly.

Only after you have confirmed your battery and crank voltages are correct should you think about equipment checks. Earths first.