Many owners of Porsche 996's will have encountered or will encounter at some point the problem of slow engine cranking.
The symptoms will be slower than normal engine cranking when cold and exacerbated when engine hot. Typically this will be sluggish cranking when first starting the car in the morning and then even slower cranking after the first stop and restart when the engine is hot.
It is logical to think first to a battery alternator or started motor problem and whilst any of those could of course be the culprit it is actually much more likely to be a different and common 996 (And even later 997) problem. I know that many 996 owners will have been told 'It's the wrong battery" 'It's your alternator" 'It's a tired starter" only to have replaced them and found that although initially there might have seen some improvement in the cranking performance it fairly quickly reverts to the same problem of slow cranking particularly with a hot engine.
What seems to be strangely less commonly diagnosed is the much more likely and much more common culprit that was even recognised by Porsche who issued a bulletin to dealers concerning the issue and that is the combined alternator/starter battery cable assembly. I have highlighted the part on the attached drawing – see item numbered 21.
The cable has a crimped joint at the starter connection and for some reason this crimped joint degrades. It oxidises quite badly and creates a point of high resistance which leads to the problem. So if you have this slow cranking issue and have already changed alternator starter or battery or had them checked and no fault can be found and the problem still exists then it is highly likely to be this cable that is at fault.
This cable can be fairly easily changed and is available through OPC's for around £60.00. When this faulty cable is changed the improvement to the cranking performance is quite dramatic as long as battery starter and alternator are in good order.
Before commencing any work you MUST disconnect the battery. Place the key in the ignition at position 1 and then disconnect the battery making sure the cable is placed well out of the way to avoid accidental contact as you are working on the car.
Now you need to remove the alternator. To do this you have to first remove the ancillaries drive belt. Use a 24mm socket and bar on the tensioner pulley and rotate against the spring to take the tension off the belt then remove the belt from the pulleys. If you are not familiar with the routing of the belt then take a picture first to aid you when refitting (Diagram attached)
If your alternator bearings are showing signs of wear then now is also a good time to fit a replacement unit. Also check the idler and tensioner pulleys for bearing wear at this stage and if necessary replace them before reassembly. Check the condition of the drive belt also. It is relatively cheap so why not replace now.
Once the belt is off you can begin to remove the alternator so as to gain access to the cable connection on the back. Slacken the top (Long) mounting bolt with a 15mm socket (The bolt is the one in the middle of the idler pulley) just a couple of turns first then give the head of the long bolt a sharp straight line tap with a mallet to loosen the clamping sleeve then fully remove it and the second 15mm mounting bolt at bottom left.
Now work the alternator out (Sideways to the left and back towards you) It can be an extremely tight fit but with a little patience it will come out. In some cars it seems to be easy just pot luck which you encounter.
Disconnect the large cable terminal and the smaller cable terminal from the rear of the alternator and place the alternator aside.
Note the slot that controls the orientation of the large cable moulded into the rear of the alternator. There are two as this alternator is also used for other vehicles so be sure to replace the new cable in the same slot position for correct orientation!
To access the starter motor you now have to remove the throttle body and front plenum.
Slacken the clamp holding the rubber intake duct from the air filter box to the throttle body disconnect the MAF plug and unclip the wiring remove the retaining bolt and remove the air intake box and put aside. To remove the throttle body unscrew the four 10mm hex head bolts and one 10mm nut fixing the lower bracket. For earlier cars with cable throttle you now remove the throttle cable from the plastic cam on the side of the throttle body by opening the throttle and rotating the cable out. For later cars disconnect the electrical connector to the body. There is also a hose coming off the throttle body that goes to a solenoid at the left press in the wire retainer and disconnect this hose. Now remove the throttle body and place somewhere clean and safe. Inside a ziplock bag is a good idea.
Now remove the front plenum. First disconnect the Air/Oil separator hose attached to the left of the plenum by squeezing the connector and pulling off the plenum.
Now loosen the outer hose clamps on the left and right of the plenum rubbers where they connect to the intakes. Slightly rotate the plenum back and force to break the seal between the rubbers and manifold. Now re tighten and do the same with the inner hose clamps to break the seal between the rubbers and the plenum. Slacken off all four clamps and you will now be able to push the rubbers over and slide out the plenum.
You now have access to the rear of the starter. If replacing the suspect cable only then use a socket and suitable extension to remove the nut retaining the large cable. You have to pull the boot back down the cable to access this nut. If you intend to replace the starter at the same time then also remove the nut securing the smaller cable the two starter mounting bolts and remove the starter.
Next job is to undo the nut under the cover on the jump start post at the rear right of the engine compartment. Once this nut is removed pull off the cable end that goes forward to the battery. Now remove the complete stud assembly that is left and that is attached to the cable we are replacing from its mount on the post. The new cable comes complete and attached to the stud assembly. Wriggle out the old cable from where it is routed behind the AC compressor and with a lot of cursing and a couple of coffee breaks to calm your nerves you will get the whole cable assembly out! Note the routing and replace the new cable in the same way.
Reverse the disassembly process as described to connect the new cable. Be sure to route the cable back exactly as it was when you removed it (Replace the starter If removed) plenum throttle body and alternator then reinstall the drive belt. I don't advise using any anti-seize on the cable connections to jump start post alternator or starter although you may do so on the starter motor and alternator retaining bolts.
After reconnecting the battery do the following. Turn on ignition for sixty seconds WITHOUT touching the throttle. Turn off and leave for at least 10 seconds before starting the engine If the battery alternator and starter are in good condition then it hopefully will crank at a speed that will please and astound you!
Now reset the electric windows by pressing once to fully close then press the close button once again briefly. Do the same to set the fully open position.
The symptoms will be slower than normal engine cranking when cold and exacerbated when engine hot. Typically this will be sluggish cranking when first starting the car in the morning and then even slower cranking after the first stop and restart when the engine is hot.
It is logical to think first to a battery alternator or started motor problem and whilst any of those could of course be the culprit it is actually much more likely to be a different and common 996 (And even later 997) problem. I know that many 996 owners will have been told 'It's the wrong battery" 'It's your alternator" 'It's a tired starter" only to have replaced them and found that although initially there might have seen some improvement in the cranking performance it fairly quickly reverts to the same problem of slow cranking particularly with a hot engine.
What seems to be strangely less commonly diagnosed is the much more likely and much more common culprit that was even recognised by Porsche who issued a bulletin to dealers concerning the issue and that is the combined alternator/starter battery cable assembly. I have highlighted the part on the attached drawing – see item numbered 21.
The cable has a crimped joint at the starter connection and for some reason this crimped joint degrades. It oxidises quite badly and creates a point of high resistance which leads to the problem. So if you have this slow cranking issue and have already changed alternator starter or battery or had them checked and no fault can be found and the problem still exists then it is highly likely to be this cable that is at fault.
This cable can be fairly easily changed and is available through OPC's for around £60.00. When this faulty cable is changed the improvement to the cranking performance is quite dramatic as long as battery starter and alternator are in good order.
Before commencing any work you MUST disconnect the battery. Place the key in the ignition at position 1 and then disconnect the battery making sure the cable is placed well out of the way to avoid accidental contact as you are working on the car.
Now you need to remove the alternator. To do this you have to first remove the ancillaries drive belt. Use a 24mm socket and bar on the tensioner pulley and rotate against the spring to take the tension off the belt then remove the belt from the pulleys. If you are not familiar with the routing of the belt then take a picture first to aid you when refitting (Diagram attached)
If your alternator bearings are showing signs of wear then now is also a good time to fit a replacement unit. Also check the idler and tensioner pulleys for bearing wear at this stage and if necessary replace them before reassembly. Check the condition of the drive belt also. It is relatively cheap so why not replace now.
Once the belt is off you can begin to remove the alternator so as to gain access to the cable connection on the back. Slacken the top (Long) mounting bolt with a 15mm socket (The bolt is the one in the middle of the idler pulley) just a couple of turns first then give the head of the long bolt a sharp straight line tap with a mallet to loosen the clamping sleeve then fully remove it and the second 15mm mounting bolt at bottom left.
Now work the alternator out (Sideways to the left and back towards you) It can be an extremely tight fit but with a little patience it will come out. In some cars it seems to be easy just pot luck which you encounter.
Disconnect the large cable terminal and the smaller cable terminal from the rear of the alternator and place the alternator aside.
Note the slot that controls the orientation of the large cable moulded into the rear of the alternator. There are two as this alternator is also used for other vehicles so be sure to replace the new cable in the same slot position for correct orientation!
To access the starter motor you now have to remove the throttle body and front plenum.
Slacken the clamp holding the rubber intake duct from the air filter box to the throttle body disconnect the MAF plug and unclip the wiring remove the retaining bolt and remove the air intake box and put aside. To remove the throttle body unscrew the four 10mm hex head bolts and one 10mm nut fixing the lower bracket. For earlier cars with cable throttle you now remove the throttle cable from the plastic cam on the side of the throttle body by opening the throttle and rotating the cable out. For later cars disconnect the electrical connector to the body. There is also a hose coming off the throttle body that goes to a solenoid at the left press in the wire retainer and disconnect this hose. Now remove the throttle body and place somewhere clean and safe. Inside a ziplock bag is a good idea.
Now remove the front plenum. First disconnect the Air/Oil separator hose attached to the left of the plenum by squeezing the connector and pulling off the plenum.
Now loosen the outer hose clamps on the left and right of the plenum rubbers where they connect to the intakes. Slightly rotate the plenum back and force to break the seal between the rubbers and manifold. Now re tighten and do the same with the inner hose clamps to break the seal between the rubbers and the plenum. Slacken off all four clamps and you will now be able to push the rubbers over and slide out the plenum.
You now have access to the rear of the starter. If replacing the suspect cable only then use a socket and suitable extension to remove the nut retaining the large cable. You have to pull the boot back down the cable to access this nut. If you intend to replace the starter at the same time then also remove the nut securing the smaller cable the two starter mounting bolts and remove the starter.
Next job is to undo the nut under the cover on the jump start post at the rear right of the engine compartment. Once this nut is removed pull off the cable end that goes forward to the battery. Now remove the complete stud assembly that is left and that is attached to the cable we are replacing from its mount on the post. The new cable comes complete and attached to the stud assembly. Wriggle out the old cable from where it is routed behind the AC compressor and with a lot of cursing and a couple of coffee breaks to calm your nerves you will get the whole cable assembly out! Note the routing and replace the new cable in the same way.
Reverse the disassembly process as described to connect the new cable. Be sure to route the cable back exactly as it was when you removed it (Replace the starter If removed) plenum throttle body and alternator then reinstall the drive belt. I don't advise using any anti-seize on the cable connections to jump start post alternator or starter although you may do so on the starter motor and alternator retaining bolts.
After reconnecting the battery do the following. Turn on ignition for sixty seconds WITHOUT touching the throttle. Turn off and leave for at least 10 seconds before starting the engine If the battery alternator and starter are in good condition then it hopefully will crank at a speed that will please and astound you!
Now reset the electric windows by pressing once to fully close then press the close button once again briefly. Do the same to set the fully open position.
