Sarasota Shark

1979 928 5 speed. Last time I took it out it ran great. Friday rolls around and I decide to take it out for my birthday. Beautiful Florida day at 76 degrees. Hit the key, it starts, then backfires through the intake and dies. It runs while the key is in start but dies in the run position. Well so it would seem. I wait a couple of minuites, put the pedal to the floor and hit the key. It starts, revs real high now with the key in the run position...backfires then dies, just not right away. So it can run in the run position. I even put a jumper wire from the post to the coil trying to eliminate any voltage drop problems, same outcome.

My first guess was timing belt but from what I can tell with the covers off, the belt is tight and no teeth are missing. I am still leaning towards a jumped tooth on the belt to cam gear throwing the timing off a bit. Messing with the belt is something I would not want to do based on possible bad guess. It cranks
fast, fuel pump cycles as it should. Just a side note, If I keep trying to start the engine I smell fuel at the exhaust tip. After four different days of trying, it is time to break it open. Before I do this, I'm open for suggestions.

Thanks, Bryant

Big Dave

Sounds like one or more cylinders are not firing, especially since you have the fuel smell. How old are your plugs/wires/caps/rotors?

Other than the backfire, what you describe sounds the same as what I experienced when I had two spark wires switched on one of the distributor caps.

perrys4

Odd that is was running great when you parked it last and now its not. It didnt slip a tooth sitting in the garage not running. Has to be something else...

Curt911

Hey Bryant, sorta OT but have you seen the black shark for sale on Bee Ridge at the little used car dealership (the one that has half a vette on the building)....

I passed by the other day and caught a glimpse, was not sure if it was worth checking out for the guys here...

As far as your prob. I don't think its a TB either... Do you know Scott at Scott's Shop? He may be able to help...

Sarasota Shark

Hello Curt,

Yes I did see the black 928 you speak of at the dealership. I went to check it out but didn't spend much time talking to the salesman. The car seemed to be ok, it had like 84,000miles. They wanted around 12 grand. He said it was an "S"
but it had an S4 wing. If someone wants more info I can check it out.

On my car the only reason I am leaning towards the t-belt is because of the backfiring. Runs flawlessly one day, horrible the next. It is protected to where nobody but my wife can mess with it. OK, stop what you are thinking. Kathleen loves the car...she would NEVER mess with it.


Thanks, Bryant

Curt911

If you need a hand with your shark let me know, I can drop by and help you troubleshoot... would be nice to get it running so you could do the W/C Fun Run with us...

jaycm

hey bryant, how long had the car been sitting since you last drove it? that is exactly how mine did when i first got it. it was sitting for about 3 years and the injectors were each clogged to different degrees.
jay

JP Rodkey

Sounds to me like too much fuel and/or air. If nothing else has changed and your belt checked out, you are having to open the throttle enough to allow air in the cylinders effectively diluting an already rich mixture. Are you seeing smoke/soot out the tailpipe? Have you checked your air bypass and cold start valves?

Sarasota Shark

No smoke or soot out the exhaust.

Curt, Give me a call (941) 780-2886

Thanks, Bryant

WER

Sounds like either the belt has jumped a few teeth or a broken camshaft... Something is allowing the spark back up into the intake where it's not welcome, and the usual path is an intake valve open when it shouldn't be. Good luck and let us know what you find out.

Big Dave

Does anyone think it's possible he may have a valve that is stuck at least partially open?

heinrich

Happy Birthday

Jim bailey - 928 International

how about the cold start injector ? the ninth fuel injector on the front of the intake .The temperature time switch in the thermostat housing tells this to shoot in some fuel to light the fire when the engine is cold. Perhaps it is leaking /stuck on or the temp time switch has failed. The VW Fox / Rabbit etc CIS cars also can have this failure.

WER

Jim, shouldn't the intakes be closed before the plug fires? So, even if the mixture in the intake was staying rich it ought to be ok unless it had an ignition source? If I'm missing something obvious, forgive me, but I'm just getting back to Porches after a 35 year break( I can still troubleshoot a 356, I'm sure).

Dennis Wilson

Try checkingthe inside of the distributor cap for cracks, sooting or signs of arcing. Did you check both cam gear marks or just the passenger side?

Dennis