'85 911 No Start

[GTGreek]

Okay,
I will start by saying I have read every forum post I could find on the subject and am still left scratching my head.

I have a 1985 911 Carrera with 63k miles. I have had the car for 1 year.

I believe the problem started at the beginning of the summer while driving the car after it had sat for more than a week, there was some hesitation in the throttle response most notably while taking off from a red light while cold then it got to the point where I would have bad response at speed. The car would run trouble free at lunch and on the way home though. I initialy thought this was just an issue with a little moisture build up in the distributor cap.

Recently I had let the car sit for about 2 1/2 weeks. I went out to install a new seat and decided to run the car for a few minutes while I worked on installing the seat. Well it would barely crank and the car ran really rough. It hunted for idle the entire time going up to as high as 1500 rpm and almost dying at 400. When I depressed the accelerator, it would take a few seconds to respond. I let the car run its course but it finally just died. I tried cranking, and it caught for a little bit but it just died. Thinking it was a lot of moisture build up in the distributor from sitting, I took the distributor cap off and let it sit. I reinstalled the distributor cap and it has not cranked since.

This is what I have done:

1. Changed spark plugs and checked for spark. I checked for spark by plugging in a spark plug to one of the wires from the distributor cap and grounding the plug. Plenty of spark.
2. Placed my hand on the DME relay and felt it click upon turning the key and then clicking a second time upon attempting to crank the engine.
3. Verified operation of the fuel pump. I jumped the fuel pump fuse and heard it run. I then had some one attempt to crank the car and heard the pump run.
4. Pulled the DME plug and check the reference sensor and speed sensors. Results as follows: Pins 25 & 26, measured 1.3 kohm and 0.1 VAC(when cranking), Pins 27 & 8, measured 1.3 kohm and 3 VAC(when cranking)
5. Borrowed a known working DME from an '86 911 and plugged it in, did not run.
6. Cleaned battery terminals.
7. Measured 12V DC at three of the corner pins to the DME.
8. All fuses have continuity.

I smell fuel at my tail pipe.
Car is cranking fine, no hesitation, battery measures 12V.

You can imagine how frustrating this is, so any advice will be helpful. I can try to find the tools to measure the fuel rail pressure but I do not know what this pressure should be.

Thanks
George

[Wil Ferch]

No need to go overboard on detail checks ( for now). Look at charging-up your battery or getting a new one first.

Fully charged battery = 12.6-12.7 volts
75% charged battery = 12.4 volts
50% charged battery= 12.2 volts
25% charged battery = 12.0 volts

Anything under 12V = "dead" battery.....

You are close to "dead" if you are measuring 12V across the main battery.

Also...check for standby current drain. Spec for 85 Carrera is 16 mA or so. Later 964's and such spec is 64mA. Some of our cars with faulty (stuck "on" relays..like PW relays) may draw more than 100-200 mA and can quickly draw down a battery after 2 weeks of non-use. To see if you have this problem, see if you can raise and lower your power windows when the car is shut down AND after you open and close the door. After you shut down the car after a drive, you SHOULD be able to raise/lower the PW as often as you like while sitting in the car. However, once you open the door...and then close it again( car all the while still shut down)...you should then NOT be able to raise and lower the PW anymore. If you can, you have a constantly-energized relay that will drain your battery.

[aston@ultrasw.c]

I feel your pain....here's some ideas

Try squirting a little easy start in the air box and see if the engine fires. This will help isolate a fuel or ignition issue.

Try changing fuel filter.

IIRC fuel pressure should be 40psi. This is a good test, try and rig something up. A jumper can be used to make the pump run, the Bentley manual will explain.

Make sure the flapper in the AFM is not jammed and can move freely. Take off the airbox and poke something in there.

Check engine grounds.

Check the injectors are actually firing take one out and watch it squirt into a bucket.

[Wil Ferch]

Sure...do all this.... but get a fully charged-up battery ( obvious easy problem) first.

[GTGreek]

I have charged battery and it is holding charge at 12.5-12.7 Volts.

I have checked the flapper in the AFM, it is moving freely.

I will start checking fuel system this week.

[E Sully]

Have you checked the cylinder head temperature sensor? 2.2-2.8k ohms?
Did you check to see what your alternator is doing? Do you get at least 13.6V at 2000 rpm?
What shape is your oxygen sensor in?
Heres a site so you can check your AFM with a 9V battery. Air Flow Meter (AFM) - from "The 944 Motronic DME" by FR Wilk

[csmab]

I 2nd checking the cylinder head temperature sensor. When mine was knocked loose during a tune up I had similiar problems like you. Once I securely attached it all was good.

CSMAB

[Tigerrat]

One more for the CHT if it has some age on it. Can cause some crazy symptoms. Also the insulation on the reference sensors. They disintegrate from heat and could cause some sporadic events.

[mackskibum]

1. Check the plugs on the left side for Reference, CHT and speed sensors. Loose CHT plug will cause a problem like you describe.

2. Check to see that the ICV is connected and functioning.

3. Check the plug on the AFM to make sure it is connected.

I know you say you have fuel and spark, but it is possible your alarm module is toast.

[GTGreek]

Thank you for all the suggestions, will start checking after work tomorrow. Will update with my results.

[GTGreek]

Okay,
Got a pair of jumper cables and connected to the battery from my truck, let the truck idle for a while and the car coughed to life. After numerous attempts the car finally cranked to life, sputtered a bit then died. This went on for about 5 attempts, each time dying after a few seconds. Finally I was able to sit in the car get in cranked and held the accelerator down slightly keeping it at 1200-1500 rpms. It seemed to want to run like this until out of gas, but when I let off the accelerator, the engine rpm would dip to about 500 and die completely. I have been able to crank it and do the same thing but each time not wanting to idle very long.

During the first few start ups there was a lot of smoke, more than my car has ever produced.

Now I am stuck with the no idle situation. Is this a symptom of a bad idle control valve? Or should I continue to check the cylinder head temperature sensor, air flow meter and anything else people suggest. Do you think I should still check the fuel pressure?

Thank you all for your help.

[GTGreek]

I am an idiot.

After many tests, a new battery, a new CHT sensor. The car would still not crank. At the end of the day yesturday I thought about checking the coil voltage again. And as I pulled the coil wire off, the wire and the plug came apart. I trimed the corroded wire back and re-inserted it into the plug and then plugged it back into the coil. The car cranked with just a bump from the key. New plug wires are ariving today.

I did get to learn alot about my car and have no fear diagnosing the next no start condition.(knock on wood)

Thank you all for your help.

[Drisump]

"Easy stuff first....always!" I don't always do this, (unfortunately) but it is almost always a mistake to jump from "A" to "H. Alls well that ends well however, and think of all that cherished Porsche time you've had. LOL

[ischmitz]

Is the idle control valve vibrating when the ignition is set to ON and the engine NOT running? If no, you have either a bad ICV or bad DME.

If yes you should feel an 80 Hz vibration with a little shake every second. That indicates a healthy idle control circuit.

Ingo