Help! Why would it just die like that?

[Kenda11]

I'm relatively new to the 911 world and need some help. I have been the proud owner of a 76' 911s since this past spring. It was a barn find with complete records and up until this past week I have felt pretty fortunate.

I regularly drive it at least once a week. This past week I fired it up and it started right up like it always does. It had been idling for about 10 minutes and as soon as I sat behind the wheel, it died with no warning. It didn't sputter or anything that would indicate there was a problem. I immediately tried to start it back up and it was sluggish to turn over and that is where I'm at. Where do I start the trouble shooting? I appreciate any advice!

[ischmitz]

Well, welcome to the Porsche "experience". Answering your question is not easy. You need to start with the basics: Your engine is a CIS fuel injected version and like any engine it needs fuel, spark and air to run. The first thing is to figure which is missing and then why it is missing:

- no fuel could be due to fuel pump, fuse, filter, CIS injection, etc. Testing can be done by providing "fuel". In other words if spraying starter fluid into the intake makes the engine run for a short time this would point you toward missing fuel.

- no spark makes an engine stop pretty sudden. Checking can be done with a tester that plugs in-line with a spark plug wire. While a helper cranks you observe the tester to confirm there is spark. Alternatively you could use an old spark plug, ground it to the engine and connect it to the spark plug wire. Then have the helper crank. Be careful not to get shocked. Removing a spark plug is not a good idea for a couple of reasons. 1.) it's difficult to get to them 2) fuel spray out of the open spark plug hole can ignite. 3) removing a plug dislodges carbon and stresses the aluminum threads.

- no air or too much air can be a third reason. However, this sounds unlikely in your case.

If the engine stopped all of a sudden my first instinct would be no spark. Make sure the CDI box makes its high-pitched sound with the ignition ON and engine not running. Inspect the cap and rotor and the trigger wire from the distributor.

Good luck and report back what you find.

Ingo

[racerboyrt]

Sounds to me like alternator is bad. When it was idling it was running off battery and now that it died it wont turn over. Check battery voltage then maybe jump start and see if it's charging. Could also be alt warning light has blown.

[Kenda11]

Thanks for the quick replies!

My first thought was alternator. I tested the battery and it was pretty low. I charged it and tried…nothing changed. Then tried jumping it and still nothing. The alt warning light comes on when I turn the ignition on and promptly goes out.

I do still get the whine of the CDI box when I turn it on. I'll look at the spark next.

Thanks again.

[racerboyrt]

So now it just turns over very slowly?

[ossiblue]

Since you tried it with a charged battery and a jump and it still didn't work, the "sluggishness" makes me think you might have some mechanical issue that is causing binding inside the engine. Try turning the engine over by hand, using the alternator pulley nut. Can you do it? Loosen all the plugs so air enters (but not debris), and try rotating the engine. Can it be done easily?

IMO, it's not likely you have a binding but it's something to eliminate if you are certain you're getting proper voltage to the starter and your electrical system is in spec. It's strange the engine would stop suddenly at idle if it's not electrical or fuel but high resistance to turning could do it.

[spuggy]

Originally Posted by Kenda11

This past week I fired it up and it started right up like it always does. It had been idling for about 10 minutes

IMHO, there's nothing good for the car in doing that (minimal oil flow/pressure, minimal air flow from the fan so localised hotspots/poor cooling, minimal alternator output) - probably why the owner's manual explicitly says to start it when ready to drive, put into gear and pull away.

[Kenda11]

The turning over slowly is similar to that of a dying battery, however the battery has a full charge.

Yes, I can turn it by hand, but it is tough. I hadn't loosened the plugs when I tried it. I typically don't let it idle that long, but it was 10 degrees out and I let it run it while I was moving other vehicles out of the way.

[GaryR]

An off chance, but does your car have a pop-off valve? Be sure it didn't pop open and get stuck in that position... Happened to me, when I removed the air box cover I heard it snap back into place. Never did see how it managed to stick, never happened again since.

[ClickClickBoom]

Simple things first!
Battery, if not fully charged, start there!
Have the battery tested by a shop, a bad cell will not charge fully and initially seem ok, how old is the battery?
The worst thing for a battery is to store it not fully charged. Battery technology is not Space Shuttle difficult but they do require minimum handling processes.
My shop is full of batteries, all on Battery Tenders, 5-6 of them.

[pors1968]

Have a look to ground cable from trans mount to the body .

[boyt911sc]

Kenda,

Do you have a CIS in your car? Keep us posted.

Tony

[porsche930dude]

check the starter connections too

[ruizyouxiey]

The alt warning light comes on when I turn the ignition on and promptly goes out.

[Kenda11]

I realized that I hadn't posted the verdict. I also have come to realize that it bothers me terribly when I am searching for solutions to problems in any forum and I find a similar issue and read all the way to the end only to be left hanging. None the less, it turned out to be the ignition. After my 3rd faulty Permatune, my local shop loaned me their Bosch test box until the issue is resolved with Permatune.

[al lkosmal]

+1 on the ground cable from trans mount to body.

regards,
al

[ischmitz]

Realize, OP just told us root cause was no-spark due to a bad Permatune. He got a Bosch CDI and the engine runs, case closed