Intermittent Start Problem

[driftguy]

Hello everyone,

I’m a long time lurker on this forum and am currently on my second Box. A beautiful black 99 with 32,000 miles. I had a 2000 but that’s a story for another time. Anyway, I’m having trouble locking down an intermittent starting problem that is just driving me up the wall. So far I have:

1. Replaced electrical part of ignition switch
2. Had battery tested (practically new)
3. Wired cable to cable clutch interlock switch to bypass it

My problem persists, and no, I have not experienced any wet carpets or water intrusion to my immobilizer box. Anyone have any ideas where else I can look? Thank you all for reading and any help you provide in advance. This forum rocks!

[Jamesp]

What are the symptoms?

[woodsman]

I've read here that the Crank Position Sensor can cause starting issues.

[driftguy]

All lights come on as normal. I have not lost function to any electrical item in the car. There is simply no crank. No noise, no clicks, nothing. Occasionally it will start first turn, but usually it takes several turns of the key. Locking and unlocking the car via the key fob seems to make no difference. The symptoms point me to clutch interlock, but now that I've completely bypassed I'm out of ideas.

[woodsman]

Originally Posted by driftguy

All lights come on as normal. I have not lost function to any electrical item in the car. There is simply no crank. No noise, no clicks, nothing. Occasionally it will start first turn, but usually it takes several turns of the key. Locking and unlocking the car via the key fob seems to make no difference. The symptoms point me to clutch interlock, but now that I've completely bypassed I'm out of ideas.

Did you check the fuses and relays ? EG. DME relay in trunk

[Spinnaker]

The first thing to check is all of the battery cable connections for corrosion at both ends. The starter draws a lot of current. If the connections have corrosion, there won't be enough amperage passing to turn the starter.
The starter might also be bad, they do wear out like any other part of a car.

[woodsman]

Check the voltage at the starter connections and compare that to the battery voltage.

[Deserion]

I'm going to say it's either the starter solenoid or the ECU not telling the car to crank (sensor). If it was the crankshaft position sensor the car should still (in theory) crank but not start.

[healthservices]

After removing the engine cover so many times now it's not a big deal but wire a test light to the starter solenoid at the starter. When the problem happens see if the light lights when attempting to crank, if it lights and does not crank, it is your starter solenoid. Replace the starter assembly

Another thing you can do is to use a large punch and give the starter a good wack, if it starts your brushes are worn out and starter should be replaced or repaired

[gavinyuill]

With a new ignition switch and battery, the only thing that could stop it from cranking would be power to the starter. Either a fuse or the starter relay in the rear.

Check the fuses first. B8, C1, C2, C3. If they are good then either the ECU isn't getting the w lead signal or the relay is broken.

To check the relay, it is number 7 in the rear relay carrier, jumper the 2 larger wires coming in, then try starting the car. If the car cranks, but no start it is the CLU not sending the w lead signal, or the ECU is broken.

If it starts, replace the relay. if there is still an issue, it is the clutch switch wiring.

With a broken CLU or ECU - time to start digging deep in the pockets.

[driftguy]

You guys are spot on about it NOT being the CPS. That was the issue with my previous Box, and it would crank but not start. I will check the relays in the trunk this evening. Today it has started flawlessly since this morning.

[woodsman]

Originally Posted by healthservices

After removing the engine cover so many times now it's not a big deal but wire a test light to the starter solenoid at the starter. When the problem happens see if the light lights when attempting to crank, if it lights and does not crank, it is your starter solenoid. Replace the starter assembly
Another thing you can do is to use a large punch and give the starter a good wack, if it starts your brushes are worn out and starter should be replaced or repaired

This is an excellent idea but if the light lights and the starter doesn't- then a voltage check should still be done in order to rule out a voltage drop problem.

[dghii]

Easiest this is to connect a volt meter to the battery (or into main at your fuse box) and monitor the voltage when you have the non-start condition (as well as normal starting). During non-start condition, a voltage drop when you turn the key, to ~9 to 11Vdc would indicate a bad connection or starter solenoid problem. If no drop is noted, the battery/starter circuit is not your issue and it's time to look elsewhere.

[driftguy]

Originally Posted by gavinyuill

With a new ignition switch and battery, the only thing that could stop it from cranking would be power to the starter. Either a fuse or the starter relay in the rear.

Check the fuses first. B8, C1, C2, C3. If they are good then either the ECU isn't getting the w lead signal or the relay is broken.

To check the relay, it is number 7 in the rear relay carrier, jumper the 2 larger wires coming in, then try starting the car. If the car cranks, but no start it is the CLU not sending the w lead signal, or the ECU is broken.

If it starts, replace the relay. if there is still an issue, it is the clutch switch wiring.

With a broken CLU or ECU - time to start digging deep in the pockets.

Checked all the fuses under the dash, everything was good and snug with no blown fuses. I changed the cruise control switch on the clutch while I was down there as well.

Checked relay number 7, it had a small amount of corrosion on it so I cleaned it with alcohol. It has started easily since then, but since the issue is so intermittent I can't be sure that mended it.

[driftguy]

Besides Porsche San Antonio, does anyone know of a good shop to take my Box to troubleshoot this problem? It did not start again on Thursday afternoon.

[Sailbrah]

Hi when you turn key on ignition did you see engine check light come on, did you get it fixed what was wrong my car is doing the same thing. If my engine check light come on car starts, if no engine check light comes on car does not do anything. Please help me to figure out the problem.

[Chris B]

Just started having the exact symptoms and issue, came across this thread when searching the forum... all electrical working, but turn the key and there is no crank, no response. Remove the key and repeat a few times, it eventually fires right up. Good to know I'm not the only one... Will check relay 7.

[DJG45458]

This is really frustrating, I have been trying to nail this down and have changed the switch and bypass...now I guess its time to try the relay or dig into the pocket!!!

[Gilles]

Originally Posted by DJG45458

This is really frustrating, I have been trying to nail this down and have changed the switch and bypass...now I guess its time to try the relay or dig into the pocket!!!

DG, this is a very old tread..

But, could you please provide more details on the symptoms and what have you done troubleshooting wise?

[Turbodad]

My problem turned out to be a weak "positive" ground in the engine compartment. It was rusty, and if I wiggled the cable and turned the key the engine would start. Disconnect the battery. It is located in a black plastic box next to the power steering reservoir. Use a screw driver to pop the box open and a 14 mm socket to remove and clean the nut.