911 Not Starting !!! - Page 2

JG911 · 08-24-2009, 01:22 AM

Any other ideas guys ?

kkinzli · 08-24-2009, 06:31 AM

I had a similar thing happening where my lights were dimming when I was trying to start the engine. It turned out to be the alternator. I would check your battery voltage, transmission ground strap, and the strap that grounds the alternator to the engine case. Another thing to check would be the voltage regulator but I am not sure your car would have one externally mounted. It might be part of the alternator. Good luck

JG911 · 08-27-2009, 04:16 PM

Another friend has suggested the Spark Box which could have gone ..... would this kill the power to the coil

widgeon13 · 09-08-2009, 03:58 AM

Did you ever get your car started, I'm having a similar problem.

JG911 · 09-08-2009, 04:12 AM

No not yet and to be honest iv not done any more with

but iv got next week off work next week so ill have a play with it then

widgeon13 · 09-08-2009, 04:18 AM

Thanks, very frustrating, let us know if you make any progress. I will advise if I find any solution on my car.

Greedy_Jones · 09-08-2009, 04:27 AM

Hi JG! i had a similar problem on my older 76 911S i changed the Coil and it started right away. Give it a try, hope it helps.

orange260z · orange260z's Garage

Maybe a similar problem with an older car.

My '70T (with a '72T motor and Webers) was running fine, and then suddenly one day shut off like a switch was flipped, and could not be restarted.

A friend came over yesterday, and after a lot of testing with a multimeter and a substitute CD box and transformer, we concluded that my problem is likely either in wiring harness between the distributor, coil and CD box; or an internal short in the distributor. We did manage to get the car running at times yesterday.

Tomorrow we'll have to check the wiring harness and distributor. I'll let you guys know what we find...

cheers,
Ayan

JG911 · 05-11-2010, 03:18 AM

Update

Last night we changed both flywheel sensors and put a new battery on and checked the coil and all working ok there

BUT

It's still not firing,just keeps turning over,rev counter very very slightly bonces,alarm bleeps ok,smell petrol aswell and can hear the fuel pump

Any more ideas please

steely · 05-11-2010, 06:40 AM

try swapping the sensors at the connections? - just in case - ask me how I know.

ischmitz · ischmitz's Garage

Sounds like you have fuel and the sensors are working. Next, make sure you have a spark.

To check for spark: Disconnect one spark plug wire, and use an old spark plug. Ground it to the engine metal while and assistant is cranking. There should be a nice spark. I don't like taking a spark plug out of the engine for several reasons:

- the open cylinder will spray fuel mist and that can ignite with rather unpleasant consequences
- taking a plug out always releases carbon and stresses the threads

You might want to wear a leather glove for better isolation when holding the plug or use plyers.

Ingo

JG911 · 05-11-2010, 04:00 PM

Quote:

Originally Posted by steely

try swapping the sensors at the connections? - just in case - ask me how I know.

How do you know lol

JG911 · 05-11-2010, 04:02 PM

Quote:

Originally Posted by ischmitz

Sounds like you have fuel and the sensors are working. Next, make sure you have a spark.

To check for spark: Disconnect one spark plug wire, and use an old spark plug. Ground it to the engine metal while and assistant is cranking. There should be a nice spark. I don't like taking a spark plug out of the engine for several reasons:

- the open cylinder will spray fuel mist and that can ignite with rather unpleasant consequences
- taking a plug out always releases carbon and stresses the threads

You might want to wear a leather glove for better isolation when holding the plug or use plyers.

Ingo

Hello we have checked for a spark and there not 1,we have tryed my coil on my friends 911 sc and it work perfect,my friend say the coil has 12v going in but nothing coing out,could it be the alarm/immobilizer

jimbauman · 05-11-2010, 05:41 PM

With a 3.2, IF you have fuel, and IF you have spark, get out the Bentley Book (mandatory) and do a check of all the sensors. You'll need a multimeter....

JB

JG911 · 05-12-2010, 01:53 AM

Quote:

Originally Posted by jimbauman

With a 3.2, IF you have fuel, and IF you have spark, get out the Bentley Book (mandatory) and do a check of all the sensors. You'll need a multimeter....

JB

We have fuel but no spark,the coil has 12v going in but nothing coming out

bezza911 · 05-12-2010, 05:10 AM

Have you got a car alarm/immobiliser? I had a similar issue, ended up ripping the thing out. 1 it was old and faulty 2, if it was stolen I would be happy to get a 993!

Also the new DME relay, make sure the one you have, even though it's new actually works, as it happened to my buddy here, we swapped his supposed new one with mine, his started fine all of a sudden, and mine did not with his new one. Problem solved, 4 days of chasing and a 30 Euro part fixed it, Oh how we cried!

bezza911 · 05-12-2010, 05:21 AM

Depending on your alarm system, there should be a key like mine (similar to those that opened the cash box on a space invaders machine) had that will hopefully bypass the system, but as they get old all hell breaks loose. It sounds to me you have trouble shot everything else but the immobiliser, ring the company who made yours or search for the alarm unit on the net, you may find some gremlins fault founded on there.

I can imagine your alarm was put on the porsche at an early age when they were more desirable for theft, just like mine, and once a fault happened, like mine, was never used again. Back up battery maybe shot if your system has one.

Just trying to give you food for thought here, sounds as though you are nearing wits end there!

JG911 · 05-12-2010, 05:38 AM

Could it be the air flow meter playing up ..

And yeh getting to crying stage myself .... all of these ideas people are suggesting are being noted and pass on to friend to start them ....

Thanks for the ideas and keep them coming :-)

ischmitz · ischmitz's Garage

If you have fuel but no spark this leaves only a few possibilities:

1. The DME is bad. (most likely)
2. Your coil is bad (you more or less ruled that out)
3. Distributor installed wrong or damaged rotor (check)
4. Bad harness (pin from DME to coil, unlikely)

Yiur condition can not be caused by an alarm unit since the fuel signal also comes from the DME and is present as you concluded. Also AFM or CHT can not inhibit spark. They change mixture.

Ingo

scarceller · scarceller's Garage

If you have fuel then the DME is alive. It also means the ref and speed sensors are also working. The DME then also creates ground pulses to the coil '-' terminal it does this via a high powered transistor the simply grounds the coils '-' terminal. Then the coils '+' terminal MUST always have +12V on it.

The best way to test for the ground pulses is with a LED test light (a normal test light may not work) you can get a LED test light at WalMart for less than $5.00 this light can also be used to test Ref and Speed Sensors.

Connect the ground clip of the light to the coil's '-' and the tip to the coils '+' then crank the engine and see if light flickers. If it does then you have ground pulses, if it does not disconnect the coil but leave the test light on the harness connectors and try again, you do this because you could have a shorted coil.

Next, the bad news: a shorted coil will almost always kill the large transistor in the DME. I have seen several DME's with the transistor blown. Also, sometimes the transistor just goes even if the coil is still good.

The AFM will never stop spark, even if the AFM is disconnected you will have spark.

Lastly, I'm assuming you know 100% that you have fuel? This assumption is very important, if the injectors are spraying then the DME is alive and running. But be certain they are spraying.

Also, another quick test for DME alive is to turn the key to 'RUN' and feel/listen to the IdleControlValve you will feel and hear it hum if the DME is alive.