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Porsche 928

Porsche 928 Care and Feeding – Chapter One – No Start Issues

There are several reasons why the Porsche 928 may not be right for everyone.  Compared to a similar vintage 911 SC, I would have to say there is more to go wrong and more to make right, maintenance-wise.  I knew this going in and was not very fazed.  After all, I’ve totally rebuilt a Jag E-Type and my 944 track car.  But to avoid immediate maintenance fun, I tried to buy a 928 in better than average condition, which I think I did.

My first months of 928 ownership were uneventful.  I bought a few backup keys.  I bought new wiper blades.  I drove it multiple times on my weekly commute from New Hill to Charlotte.  No issues.  Until… one Friday night I went out to fetch the car around to take my wife out to dinner.  It wouldn’t start!  It cranked and acted like it was trying to fire and run, but run it would not.  We wound up taking her dead nuts reliable Cayman S.  Oh, the ignominy.  The next day I started making some basic checks.  I fully charged the battery, which was getting pretty weak from all the cranking.  I cracked the nut at the front of the fuel rail to confirm pressure.  I had fuel.  I hooked up my inductive timing light.  I was getting a spark (or enough of a spark event to fire the timing light).  I eventually checked all 8 spark leads.  All were firing.  I began reading no start threads on Rennlist furiously, looking for clues.   At one point, Neal from the 928 Owners Club came over and we went through just about the entire drill:  Checked fuses.  Checked relays.  Injectors were clicking.  Fuel pressure was there.  We swapped out the DME and the ignition control unit into his similar car.  Both were fine.  We checked for a broken or skipped timing belt.  We checked basic ignition timing.  No luck!

The next day I wanted to do a better job of checking the ignition timing, since the car acted like the spark was very retarded.  On my 86.5, the timing marks on the flywheel are obscured by the bracket for the throttle linkage.  I took the bracket off so I could get a good aim with the timing light.  I had my wife come out to crank the car while I observed the timing marks.  15 seconds after she started cranking the car, it started up.  A little rough at first, then it settled into a smooth idle.  WTF.  As far as I know, I had done nothing different.  Maybe she is the Porsche Whisperer,  I don’t know.  I had her shut it off and try again.  Fired right up.  Wow! Strange happenings.

My confidence shaken, I left the car in the garage and came out randomly for several weeks.  It started every time.  Not happy with a non-diagnosis, I decided to clean all the engine ground points and to replace the battery ground strap.  I did this using an excellent tutorial that is on the Rennlist 928 forum “sticky” New Visitor.  This is a really good tutorial on many subjects regarding the 928.  In the process of cleaning the grounds, I found the closest thing to a smoking gun in the entire process.  The 3 way connector at the rear of the engine for the crank sensor pretty much fell apart in my hands.  It was held together with electrical tape and tie wraps.  I installed a new sensor, which got me a new plug.  Strangely, the connector on the engine harness side was in very good shape.  So I can conjecture that the poor connection at this plug was indeed confusing the ECU causing a random no start.  I also found the same type 3 way connector at the front of the engine for the throttle butterfly closed/WOT switches in similarly poor condition.  I replaced this one by buying a replacement connector from Roger at 928srus and wiring it into the existing harness.

Whatever, the sum of these various actions have resulting in no more no-starts since the initial episode.  My confidence is starting to return.  We’ll see how it goes.


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