engine diagnostics

[scott.k]

I am trying to figure out the problem with my car. It is a 1980 911 sc. I just put the engine back in and when I try to start it the starter motor spins but the engine doesn't start. Just a little background. While the engine was out, I took out the ac, heater, and cruise control. I took out the ac parts but I did not do anything to the ac electrical unit. This is the same for the heater. For the cruise control, I took out the cylindrical shaped vaccum part from the engine comartment but that is all. The engine was out for about a month and a half to two months. Im not sure if the fuel in an injector could clog in that time? Any suggestions? or anything that I may not have thought of. Anything helps.

I am guessing that it is some type of wiring issue because the engine doesn't even turn over.
Thanks
Scott

[Steve@Rennsport]

Scott,

Some clarification is needed to help diagnose your car.

1) Starter engages but doesn't crank the engine?

2) Battery voltage above 12.7 vdc?

3) Battery terminals clean & shiny?

4) Battery cables clean & shiny at their respective grounds: one by the battery and one by the transmission mount?

After thats all done, will it crank the engine?

[stlrj]

"...because the engine doesn't even turn over. "

Try jumping it.

[Joe Bob]

The engine doesn't turn over but the starter does?

Didya fergit the ring gear on the flywheel?

[James Brown]

Nice one Joe, that's the first thing I though of when I saw this.
Scott, gremlins are most prolific when the engine is out of the car. they love to frolic around and breed in the cold engine. Best defense is a good offense, get that thing running as soon as possible!!

[scott.k]

The starter spins but the engine doesnt even try to start. I didnt forget the ring, im not sure why it isnt even making an attempt to start. Im guessing that it may be something with the ignition system wiring or something like that because otherwise the engine would be at least trying to start. Im not sure though. I think its something electrical

[James Brown]

Wait, the starter IS turning the engine but it's not starting? is that correct?

[scott.k]

I guess turning may not have been the right term. The engine is spinning shown by the fan but Im guessing that the ignition is the problem because it isnt sparking at all

any ideas what it could be?

[Joe Bob]

Turning at normal speed?

Have you pulled a spark plug lead, put a good plug in it and grounded it, checking for spark while cranking the engine?

CIS needs spark, fuel pressure and air.

Is the fuel pump cranking when you lift the flapper in the air box with the ignition on?

[scott.k]

Yes I believe that it is turning at normal speed and the fuel is being pumped in. I dont think that the plugs are sparking and I will definitely try pulling out a spark plug and starting the starter motor and see if it sparks. It it doesnt, do you have any idea what it may be. Any specific wiring/connections I should look to first?
THanks

[scott.k]

ok, thanks, I will test the plugs out of the engine for sure. Im not sure I follow the CDI box testing instructions because Im not familiar with all of those terms but I will see what I can do.

THanks for all the help

[Joe Bob]

Might want to get a Bentley manual...it helps.

[scott.k]

I agree, I will try to get one

[Bob Kontak]

Pull the connector on your CD box and examine all of the individual connectors in the female six pin socket. The individual connectors can slip back out of their resting points and lose the connection even though everything looks ok from the outside.

Also the 14 pin connector (far driver's side rear) can have the same problem. Un-plug it, pop it open and look at the leads. I do think there may be a pin or two in there that can kill the ignition.

From your original post you did not touch the distributor so ignition timing should not be an issue?

Your problem is simple. Just a matter of finding it and that can burn some time.

There are electrical diagrams for an 82 SC in the tech info center that you can view and trace down gremlins.

Permatune has a nice trouble shooting section that you can use to drill down in on ignition issues.

Perma Tune High Performance Ignition Systems

[scott.k]

No I did not touch the distributor and I agree with you. I think it a a pin somewhere that I will have to look for. THanks a lot for the help.
Scott

[lucittm]

Make sure you have +12V on your coil with the key in the "On" position, you can check this by pulling out a stop lamp and grounding one of the contacts on the bulb. It may need to be cranking on some models, I can't remember for the SC.

If you don't have the +12V, the ignition pulse from the CD ignition box won't matter. You may have a bad fuse, relay, or wire. Pretty much, they fail in that order.

Good Luck,
Mark

[scott.k]

I just tried starting the car with one of the spark plugs out and I left the ground attached on the engine (by the fan). It did not spark. In doing this, I found that the spark plug wires connect to a metal, rubber coated elbow shaped piece which connects to the plug. On the plug I pulled out, I first pulled out the elbow piece and found that the connection of the elbow piece to the plug wire was green and corroded. That can't be good! So I cleaned it out some and did the spark plug test. Did the corrosion cause the plug not to fire? Do you think all of the elbow pieces are life this? Also, there is a connector with 6 pins on each side that are housed in little rectangular black plastic boxes. This is located in the engine compartment by the drivers side shock tower. There are 6 wires on each side of the connection. A blue wire with white stripes, and blue wire with green stripes, a brown wire, two black wires with red stripes, and a green wire. Do these connect according to color? Because when I took the engine out of the car I accidentally pulled one side of the connections by the wire which made all six of the wires come out of the black, plastic housing so I could not see which one went where. I reconnected the according to color but there are two black and reds and I tried both possible connections and it did not start either way. But if they are not supposed to be connected according to color than Im way off.
Please let me know if you have any suggestions.
Thanks
Scott

[scott.k]

I dont have a multimeter but should probably get one now. Do I need to have the car cranking when I am testing for 12v in different places? Also, how do I test resistance on the plug wires? What would resistance on plug wires mean?
Thanks

[Joe Bob]

How to Test a Spark Plug Wire on a Car | eHow.com

Generic wire test proceedure. BUT Porsche uses a Capacitive Discharge (CDI) and various wire manaufacturers deal with it differently.

An ohm test WILL find one or more wires with a wide difference in range of ohm resistance. But you still need a range from the manufacturer to see if they are ALL in spec. As to 12v when cranking....depends on where you are testing. Again, the manual tells ya where and when to expect 12v.

Kinda like the Spanish Inquisition.....(Monty Python)....you never know when to expect.....

[RSWiser]

Is the starter engaging the ring gear?

I had a starter that would spin but would not engage the ring gear.