Slow starting issue has reared its head again, positive lead

So I thought I had got away with my slow starting issue, it had been fine for a while and was starting up easily hot or cold. I spent a week in the Alps and had a couple of hot starting moments again but it does always start up. It is just very slow on the first turn of the starter and then progressively gets faster and then fires up, it has never not started yet but I fear that it may let me down soon as it has started doing it on cold start now too? I'll upload a video to show how bad this has got again. This was originally covered in my engine rebuild thread but I thought it best to start another thread just for this so it doesn't get lost in that other thread. Last night I started researching my positive side cabling as I have already replaced the two earth cables from engine to body and battery to body, which originally did help the slow starting and also the battery is new. I also had my starter motor tested and rebuild and this had a new brushes ring fitted, I am thinking of taking that off again and having the solenoid changed just to eliminate that? I have found what I think is 4 positive cables, battery to bulkhead distributor, bulkhead distributor to under the car on the nearside, n/s under the car to distributor in the engine bay and from there to the starter and alternator. There is a difference between LHD and RHD cars and prices seem to vary widely depending on where you get them from. Battery to bulkhead distributor P/N 99661209010 £28.27 Bulkhead distributor to under the car on the nearside. P/N 99661209113 £72.36 n/s under the car to distributor in the engine bay P/N 99661209201 £69.74 Starter and alternator cable. P/N 99660701903 £62.30 I was planning on doing one at a time to save the cost of just replacing them all in one go, I was a little worried about getting to the underside of the dash connection as I've never seen this, there seems to be distribution block there? I know where all the other ones are so not too bad to get too. One other option is to make my own using the original plastic protection sleeving and I have the crimping tool to fit the lugs and heat shrink for the ends but I'm not yet sure what the wire gauge of the cable is to buy, doing it this way would let me replace them all without the cost worry, the only one I would probably have an issue with is the starter cable as it is spliced into at the alternator and has the cast aluminium/copper part at the starter, something I couldn't replicate unless I just use standard connections piggy backed instead? I'll try to find this issue (again) and further document as I go

My car also does the slow start thang if it is hot, always starts if the battery is in good condition so it's still on my list of things to do. From everything I've read over the years it seem as if the Starter & Alternator cable is at fault, I've seen pics of the old failed cables with corrosion creeping up under the sleeving. There are online guides to help replacement, I believe one of the tricks is to pour hot water over a black plastic block on the old cable so that you can peel the cover off and get to the fixing.

Re: Slow staring issue has reared it head again, positive le If I was going to do just one, I'd do the starter and alternator, as most likely to be damaged by heat. You could check and clean the connections of all the others as well.

Does your voltage gauge drop when the car warms up? Mine used to start around 13.5 and as car warmed up drop to less than 13v. I ask as this is a really good indication the starter / alternator cable is bad. After replacing over 2 years ago, I see just below 14v cold and perhaps 13.8v hot with all accessories on. If you have good voltages hot and cold showing on the dash, I would suspect you could rule out the starter / alternator cable or drop further down the list.

Is the starter and alternator cable the infamous "Y cable" which often seems to be the culprit of slow starting? I noticed my 98 C2 turned over slowly when hot the other day, so this in on my list to check when it goes up on stands for the gearbox removal.

I have never worked upon a water cooled Porsche electrical circuit, other than on a 928. Using base principals if we start by proving the battery is well up to the task in that it`s voltage does not drop considerably WHILE the engine is being cranked (measured directly on it`s terminals and NOT on any part of the clamps), then unless the battery has an internal issue at least you have hopefully established a foundation from which to base your test regime..? Why not measure from the clamps...? As the clamps are the first CONNECTION in the system the issue could lie there..? . Each and every connection has the potential to introduce RESISTANCE to the flow of electricity and more so if it is in any way loose or showing signs of corrosion, the corrosion often not being obvious at first glance, but still existing between the faces at the point of contact. The electrical term CIRCUIT is just the same as a race track in that it starts and ends logically enough at the start/finish line, and in this case the start and end are both battery terminals, thus the EARTHING side of the circuit must be regarded as an equally important part of the circuit as the positive insulated cable side. For sure we all know that Earths are important and a likely cause of issues, but bear in mind that the earth is required to carry the same amount of POWER as the heavy battery lead, and never more so than when cranking the starter...Once again every connection on the route back from the starter motor`s casing, all the way back to the battery negative terminal has the potential to introduce RESISTANCE, and those earth connections can be exposed to the elements a tad more than the equally important connections on the positive side. Of course cleaning off protective paintwork at the point of connection to ensure it is clean and tight to the chassis exposes the chassis to corrosion, however if once the connection is made clean and tight, you could paint over the whole area or slobber it with grease to keep corrosion at bay..? Corroded bolt threads into the chassis, and corroded washers clamping an earth lead, can introduce RESISTANCE. Running a tap down chassis threads to clean them up can improve things a bit..? How many connections are there between the starter and the battery on the positive and earthing side of the whole circuit..? Any one of which can create RESISTANCE to the flow of electricity, and wherever there is RESISTANCE, the voltage will drop across that resistance, and each and every connection in the whole CIRCUIT has potential to introduce resistance, if beginning to loosen due to vibration or corrode to ANY degree.. When looking for starter problems the four key terms would seem to be, POWER which the battery supplies, RESISTANCE at poor connections, which generates HEAT when under LOAD, all of which together equates to a drop in voltage available at the starter motor. causing it to turn slowly There have been pictures available where a heavy starter cable looks to be in good condition but on closer inspection when the heat shrink is peeled back at the point of connection it can be seen that there are signs of heat being present, enough to begin to melt the edges of the insulation, or discolour the copper cable it`s self..? This decolourisation due to the presence of resistance and the heat generated, can work it`s way along the length of the cable in time until it eventually introduces ever increasing resistance to the extent that the starter will reduce in it`s ability to turn the engine over... I appreciate that it would be time consuming to check every connection, though when fault finding discounting the earthing circuit as the source of the issue can be relatively simple by providing a temporary earth using jump leads to link all the way from the earthing point near the battery to the metalwork of the engine at some suitable point capable of carrying the LOAD of the starter, and not some thin bit of tin.. An ASSUMPTION being made here that the battery has been proven capable and that connections between the negative terminal and the earthing point are also clean and tight. tThe fewer assumptions made the better when tracing faults.. Unlikely that any single jump lead might be long enough, but hopefully simple enough to join two together using their spring clamps. As ever a bit long winded though the issue can be the seemingly intermittent as a loose/dirty connection can have a variable effect, and the effect of more than one less than perfect connection can be cumulative in that the voltage can drop at each connection in turn and if you add the variability to that, you can understand the possible difficulty in determining the actual cause..? For example if one bad connection is found and replaced things will show a sign of improvement, yet there may be other connections part way along the route to failure. Using a simple meter to try to determine the resistance of the circuit(using OHMS) seems less than ideal as it is only really when under LOAD (starter cranking) that the resistance can build producing heat. I guess accessibility can determine that replacing more than one lead at a time may be less than ideal when trying to determine the slow cranking issue using a replacement process as opposed to looking for the actual fault(s) The solenoid mounted on the side of the starter has a few connections and it acts as the switch controlling the the heavy action of the starter via internal contacts and which can and do burn internally over time, but are well up to the task for many many operations without introducing fault. The solenoid is available as a separate Bosch part for many starter motors, and in the grand scheme of parts for Porsche, seems relatively inexpensive..? All of which can be further complicated by the reality that determining the battery condition/voltage at any one time does not equate to it being in ideal condition the next time the starter fault arises , given the many variables in terms of the number of different systems making demands on the battery and the length of time they have been doing so, equating to the voltage available dropping, and creating yet another variable to contend with..? Perhaps best to ever start of by measuring the battery with a stand alone voltmeter across the battery terminals when attempting to trace a slow starter operation..? Hope I have not muddied the water any and I am more than happy to be corrected.

How do you know it's the starter side of things that's the problem? I had a problem with my scooter turning over. I disconnected the ignition system and it'd turn all day long without a problem. As soon as it had to generate a spark, it'd be sluggish again. I've also tested starter motors on various cars I've owned by shorting across the starter posts and had them spinning the engine fine. Soon as the ignition system is reconnected, back to slugish turnover. That way you can eliminate anything else that may be causing the problem. Just a thought.

I get where you are coming from Alex, though I imagine if the battery is in serviceable condition it should of course handle all the normal loads placed upon it, however if there is some other fault drawing a high current when the ignition is switched on, then that equates to less power available for the starter..? There are so many electrical variables at play, and ever more so since the inception of digital programming. In my 991 when I touch the door handle all sorts of circuits come into play, and if I open the passenger door and open the glove box I hear a digital whine which could be thought to be the fuel pump, but unless I know the programming it`s anybody`s guess..? Measuring the battery voltage at the start of fault finding would seem to be key, and in the sort of case you mention Alex, it can be worthwhile to can be repeat the voltage checks after the ignition is switched on, and the difference noted..? A quick check could be to switch the headlights on and then try cranking the engine to note the possible change due to a drop in battery efficiency...?

It was a faulty coil pack/lead on my scooter.

I've just been out in the dark tinkering a little as I wanted to make a start before the weekend. I removed the airbox, throttle body and inlet tube to gain access. I started at the Y cable as mentioned and that seems to be fine, I had cleaned all the connectors up when I had the starter off recently and also when I had the engine out so I thought I would have noticed if it was corroded, I pulled the rubber cover off and it looks okay? The only part of this cable I hadn't checked was inside the heat shrink on the jump post cables in the engine bay but again this looked fine, no corrosion like I have seen before on the negative leads I have already replaced, just shiny copper cable. I next looked at the battery to bulkhead distributor lead, I removed the heat shrink from the battery end but I was unable to get to the cover for the other end at the bulkhead. This did make me wonder though as I had blocked drain plugs around this area a few years ago and had water ingress into the cabin, The nuts for the distributor also look a little rustier than any other parts in this area. I'll have to look into how I can get this off but there are AC pipes and wiring all around this in quite a tight area, circled in red? @ Luddite, I do still need to do further testing of the system but I thought this may have been a quick win tonight but it hasn't highlighted anything as yet. I'll run through what you have written in daylight. Also @ 911-C2, I haven't checked whether the voltage drops when the engine is warm but that is something to check and I'll report back on this. @ Alex, I'm assuming I am now dealing with the plus side as I had good results with new earth cables, new battery and starter rebuild and now I'm guessing the positive side may be under more pressure to perform if failing with age?

First off, per the other thread, I had identical problems. Mine was a combination of a bad alternator where the regulator would get sick as it heated up. On startup, I had 14v and it would very gradually move to 12. The other issue was the tired starter. I would stall it, try to start immediately and it was barely turning, release it, give it 5 seconds and it would start a bit easier...very confusing and annoying. Eventually disappeared post rebuild with starter replacement although for obvious reasons, having a good alternator improved things a bit pre rebuild. Per the above posts, the well-known culprit here is the starter/alternator cable. Your problem per your initial post is hot starting. Resistance increases with temperature. The engine bay is where the temperature increases when you are driving the car, so for good order let's start in the engine bay. Ruling out the battery, Things in the engine bay involved in the starter motor circuit - Starter Motor Starter/Alternator Y Cable You have rebuilt the starter motor so while we shouldn't rule it out completely, we should look at the other option (and the usual suspect) - the Y cable. While it looks nice and shiny, the problem occurs inside the crimp where you cant see it. A possible troubleshooting workaround is to make up a temporary (cheap) cable and install it in parallel if the terminal bolts are long enough to facilitate a second eyelet. if the problem disappears you have found your culprit. I do think though, it's worth just replacing it as the hard part is the access, so if you are in there anyway... The troubleshooting way would be to check for a voltage drop on the Y cable when cranking by putting the multimeter in parallel its hot, but this is difficult and I'm not sure if the average multimeter can handle a starter circuit when cranking. The possible reason that the problem went away temporarily could be that the cable has always been the issue, but when you repaired the starter and replaced the battery, they were enough to overcome the resistance in the cable at that time. However, the cable is constantly corroding and getting worse at each start and now it is at the point where the resistance is too high for even the rebuilt starter and battery to overcome. Just something else to consider.

This was my plan for tonight, make up a cable to jump between the rear of the starter and joint for the jump start point in the engine bay, There may be just enough thread on the starter to do this? But I do also have my suspicions that the battery positive lead was submerged in water for quite a while so may be the one I need to remove next to inspect?

No harm in cleaning the battery lead. All individual resistance points will add up to the point where when you add in a hot engine bay, it becomes too much.

I also just checked using a multimeter - you won't fry it as you will be doing a voltage drop test. The dummies version is that you connect the volt meter from the positive terminal in the engine bay to the positive on the starter. Get someone to Crank the engine while you look at the meter. All of the volts should go down the starter cable and you should only see maximum 0.3V on the multi meter screen. If you see more than .3v on the meter it means that the full voltage won't fit down the starter cable because it's a bit blocked by resistance. Goggle starter motor voltage drop test https://www.aa1car.com/library/voltage_drop_testing.htm

A beautifully simple video - worth a watch Infrasilver - it will help you systematically with a process of elimination. 10 minutes watch and you'll be good to go https://m.youtube.com/watch?v=WMXENKujYtc