83 911 SC died won't restart

[911 Camper]

Last week on my way back from lunch I was stopped at a stop light and when I let out the clutch to go the car just died, it was like someone turned off the key. When I tried to restart it it cranked but never fired. I towed it home and have started my search for answers. Here is what I know:

1. I am getting fuel, I can smell it and if I pick up on the air plate I get all of the injector Noise.
2. The CD box is singing away like usual.
3. When I pulled the coil wire ( the main one to the distributer) and hold it next to the bolt on the fan housing I get a slight spark while cranking over the engine. I almost have to touch the wire to get it to jump.
4. When I crank the engine the tach jumps to 3000 or so rpm's and slowly climbs to 3500 or 4000 and acts erratic(sp).
5. The distributor ignition trigger wires read 555 ohms and changes as I move the distributor, when it is out of the car.

I have started to believe that the CD box is bad but it is singing properly. The CD box is a Bosch 6 wire. I don't know what the volage at the A side of the coil should be when the engine is cranking and I don't have an ocilliscope, my fluke 73 reads less than 1 volt DC. I know I am missing something.....HELP.

[Joe Bob]

Fuel pressure?

[AngM018]

The green wire of death?

It is infamous for leaving SC owners stranded. If its not still green in color, and/or it is brittle, then replace it.

[911 Camper]

Fuel pump is working and I cracked an injuctor line and got fuel. I have not checked pressure with a gauge though. I have a hard time believing that the pressure could go out of spec in one instant swoop?

[911 Camper]

Which green wire?

[Superman]

The one that runs from the side if the distributor to the CD box near the fuse panel.

[Aurel]

Here ya go:

http://forums.pelicanparts.com/showthread.php?t=334432&highlight=green+wire

My money is on the green wire too. Let us know how it turns out.

Aurel

[911 Camper]

Guys, I appreciate all of the input!! I have tested continuity on this wire and it was good. I take it that this doesn't seem to matter. I went to the link that Aurel posted, great info. Has anyone figured out the best solutiion for building a cheaper green wire?

[Walt Fricke]

Camper

Pull a plug, hook the wire back up, and see if the plug is firing. This should tell you that spark is hot enough, the distributor parts work, and you are getting some sort of timing action.

Checking fuel pressure would also be good, but you've got to have the setup for that (not expensive, but will take a while to get to you from JCWhitney or other sources).

Pull an injector out, reconnect to the line, and stick it into a container. Turn on key, remove air filter, and press the air metering plate up. See if it injects, and if injection increases with plate height. If there is enough pressure to squirt past the spring loaded setup in the injectors, chances are good your fuel pump is putting out adequate pressure.

I assume you have checked the battery. I infer that it will turn the engine over. A wierd tach sometimes indicates low overall voltage.

A guy recently solved a similar issue by checking the connections to the CD box. One had crud on it, or one wire was manky, or something.

Good luck.

Walt

[AngM018]

I purchased the green wire from Pelican. it was about 60 bucks I believe. Then I bought a connector from eagle day and used television coax cable to run from that connector to the CD box.

[Superman]

Originally Posted by Walt Fricke

Camper

Pull a plug, hook the wire back up, and see if the plug is firing. This should tell you that spark is hot enough, the distributor parts work, and you are getting some sort of timing action.

It's even easier than that. Pull the wire from the center of the distributor cap and hold it near the any grounded metal. Hold it with a pair of insulated pliers. A snappy blue spark should jump the gap. If it does, then your green wire is not the problem.

Think of it this way. An engine just needs three things to fire.

1. Compression (should have this unless the engine internals are TOTALLY worn out)
2. fuel/air mixture
3. spark

If it gets all three, it will fire. The problem almost always #2 or #3. Usually #3.

[911 Camper]

Superman, I do get spark when I use your procedure, #3 of original post. I have an inline spark tester and it lights as the engine cranks to each cylinder and from the coil. What is making my tach go nuts; #4 of original post. the green wire looks good. no crack and it tests good for continuity.

[Ohio911]

I could be wrong but sporadic Tach signals sometimes indicate charging problems I.E. alternator and or voltage regulator or maybe even cdi? Thats where I might look.

[Superman]

Originally Posted by Ohio911

I could be wrong but sporadic Tach signals sometimes indicate charging problems I.E. alternator and or voltage regulator or maybe even cdi? Thats where I might look.

Sure, but during starting, before the alternator comes up to speed, the system is running on battery voltage, which is pretty stable.

I once had a spark that would occur at 1 atmosphere, but would not occur in the pressures of a cylinder. That is why we suggest you make sure it is a snappy blue spark. If so, it's got plenty of power.

If you've got spark, then you must not be getting fuel. Put the key in and turn it to "on." Remove the air cleaner and push the sensor plate upward. Briefly. Do you hear the injectors singing? They make a sort of whining sound.

[GothingNC]

Have you swapped the red fuel pump relay with a black one?

Also try what Supperman says, you should here the fuel pump kick in with the key on and the sensor plate lifted.

[911 Camper]

Superman, I think you may be on to something! The tach behavior baffles me and may be the key tell tale of the porblem. I have lifted the sensor plate and I do get the injection Chaos, and I do get spark, snappy I don't think so. I have to basically touch the coil wire to ground to get to arch. Could I have a bad ground to the tranny? Is there a ground strap to the motor? Is there anything behind the dash that may cause this? Could the CD box be sending a false Tach signal or be shorting the trigger signal to the Tach? Why arn't the Porsche Gods smiling on me? (sorry)

[Sapporo Guy]

errr, maybe just plain dumb, but I've had the pop off go and just putting back in place got me on the road again.

1 time though, I had nothing ... just idiot lights:P
I fiddled with the positive on the battery and it worked again.

Another time was no good and only idiot lights. A push start got me going for some reason ... ???

I hope it's just something simple!

[GaryDG]

Sorry all. but what is the "Green Wire".

The pressure teter refered to in a previous post is on JC WHitney at the following location for $60 +Shipping

http://www.jcwhitney.com/autoparts/Product/Pr-p_Product.CATENTRY_ID:2008126/c-10101/Nty-1/p-2008126/Ntx-mode+matchallpartial/N-10101/tf-Browse/s-10101/Ntk-AllTextSearchGroup?Ntt=fuel+injection+vacuum+teste r

[911 Camper]

It's the ignition trigger wire that runs from the distributor to the CD box. It is a sheilded green wire that tells your CD bos when to discharge and send voltage to the transformer (AKA coil) and ultimatly to the plugs

[911 Camper]

Thanks for the link Gary!!