An intermiten problem at best
 

I thought I'd try the forum and see if anyone has any ideas, my shop is just scratching there head. Ill turn the key to start, all the dash lights light up but no action from the motor, absolutely nothing, no cranking noise or anything. I'll leave the car for a day or two and try again and it'll fire up. This problem only happens 3-4 times a year and runs as per normal. My car is a 99 but had a 996 3.4l crate motor installed 6 years ago, the problem seems to happen at the most inconvenient times and does it even when the motor is hot or cold. If anyone has any suggestions I would greatly appreciate it.......

Has the ignition switch been replaced? When they go bad, they can cause all kinds of odd behavior...

Replace Ignition Switch

Yes, that was where my shop started, replaced the ignition switch, we thought maybe that was it because the problem only surfaces 3-4 times a year but then at my brothers wedding it happened again....lol

Clutch interlock switch (near clutch pedal). The switch signals that the clutch is depressed and allows the engine to start. When the switch starts to fail, the engine occasionally won't start even when the clutch is depressed. I spent 3 months tracking this down on my car. Its cheap and easy to replace.

x2 on clutch interlock switch. As stated above, it's cheap and easy to replace.

Until you replace if it happens again, just loosen plug on the back side and run a jumper wire between the contacts but MAKE SURE IT'S OUT OF GEAR BEFORE TRYING TO START or clutch is pushed in.

Good luck :)

Your car may be haunted?

Your moniker seems like you can handle it tho!

My guess would likely be a a ground fault somewhere within the electrical system. Most likely the casualty of the replacement engine. Easy to explain, hard to diagnose. Where are the Jaguar mechanics when you need them? They have horrible electrical issues - mechanics spend hours under there testing circuits. Those are the worst!

Start with the starter, then battery.

Just a guess.

I'm not a mechanic, but I did stay at Holiday Inn Express last night.

Maybe should try replace ignition switch again, there's different quality on them...
I replaced a new one 6-8 months ago, and went broke again.. it made AC heater run all the time and drained the battery..

Replacing the clutch pedal sensor was the only other thing that was replaced. I have had one other niggle that might help diagnose the problem and when it happens it coincides with the start issue, which happened yesterday. Got into the car, cranked it over, car started for a couple of seconds and then died. Tried to restart and nothing. As soon as the car has an episode and finally restarts I rush it over to the shop to read codes and of course, everything comes back as a healthy car...... Thanks for the input guys, really appreciate it, hope I can get to the bottom of it, my Porsche is taking a moral beating from my Audi and BMW neighbors.... Lol

Could there be something wrong with the immobilizer transponder in one of your keys? Or possibly an intermittent electrical issue with your central locking unit? I was just reading this thread which is somewhat similar to yours, except that his car suddenly went totally dead.

Then again this guy technically just had a short in his radio that caused all his problems...

Wow, thanks for the post, I read his story and it definitely sounds like my story. I'll be spending sometime tomorrow in the garage troubleshooting, I'll post what happens..... Thanks again......

Well, after 2-3 days of going through the paces, ignition switch changed, clutch switch bypass, central locking unit analyzed, dash pulled apart looking for problematic grounds. It looks like a sticky fuel pump relay was the culprit. Well, after we pulled it out and checked it, then re-installed it the car magically started...... It could be that my car just felt it was time to start but we are ordering a replacement and hoping that is it...... Thanks again for everyone's input.