Sorry, still have 911 running issue

[1upracing]

1980 911sc (T) sat from 99 until now in my father-in-laws garage.

Ok, so after replacing the alternator, fuel with clean fuel tank, fuel filter, spark pugs, and vacuum lines the car ran great six consecutive times in a row. Then all of the sudden it started running rough, I shut it off and it wouldn't start for three days.
Its getting fuel, and when I went to check for spark on the third day it started. (ran rough, but ran) I did place the tester on the wires and sometimes it appeared less than desirable.
Would a coil going bad or wires going bad cause this behavior?

So now what???

I'm new to this 911 stuff, normally a chevy v-8 type, but I'm willing to learn.

[1upracing]

Someone must have some Idea?

[ruf-porsche]

During the 7 years that it sat in you father -in-law garage did anyone start it up occasionally to run the engine? When it ran badly was there a lot of black smoke?

The fuel system is probably contaminated with old fuel and some of the old fuel. The old fuel may be causing the piston in the FD to be stuck in a certain position (usually up) which will cause the engine to flood.

Do a search on stuck piston FD and you will find the answer.

If you Edit your profile and list your location, perhaps another Pelican member can assist you.

[1upracing]

it did get ran on occasion. No black smoke whatsoever. A smidge of white smoke, only after sitting for a couple of days.
The car was stored with less than a gallon of gas and that was flushed out.

Sometimes it runs great and sometimes it just runs like crap. It seems to be a bit moody.

[gabenheimer]

Did it just run rough or was it backfiring and popping? Did it smooth out with throttle or run worse? When it started last, did it start right up or did you crank it for a while? Is the battery new? Take off the distributor cap. Are the electrodes excessively pitted? Is there water inside the cap? Did you push the plug wires on all the way when you changed the spark plugs?

How many miles are on the car? With the engine running (if possible) at night, look in the engine compartment. Do you see sparks from the spark plug wires? This occurs often with bad wires.

Initially it sounds to me like a fuel problem, but lets try to eliminate other possibilities first.

My car has the later motronic injection but there are tons of members here with the CIS found on your SC.

Randy

[unclebilly]

My guess... plugged up fuel filter. Have a look inside the tank to see how clean things are in there.

I had a vehicle that sat for 9 years. When I got it running, I ran it for a week and everything was A-OK. Then I added some injector cleaner and it losened up all the rust scale in the tank and kept pluging fuel filters. I had quite an adventure cleaning out the tank and eventually installed a Racor filter that I could remove the bowl on to clean it out.

[1upracing]

Did it just run rough or was it backfiring and popping? Yes to both.

Did it smooth out with throttle or run worse? Smoothed out with higher rpm's.

Yes, New Battery.

Fuel tank is clean and installed new fuel filter.

When it started the non starting thing it would only turn over for three days. Then out of the blue it fired right up on the fourth day.

The cap looks fairly new with no corrosion.

[JohnKo]

On the theory that it's a fuel issue caused by lots of sensitive CIS bits sitting around too long in old fuel, it might be worth adding a bottle of Techron; since the situation sounds marginal and acts like intermittent, that may even be a fix. Probably can't hurt.

Good luck!

[1upracing]

Tried the fuel additive too.

Sometimes it runs like there is nothing wrong and then bam it starts running like crap.

Sometimes it wont start and then I come back and it fires first try.

I don't know.

[ruf-porsche]

Check the green wire.

Why was it park at your father-in-law's garage for all those years? Was there a problem before it was parked?

[1upracing]

No problem. Just no interest in driving it. Thats why I have it now.