911SC No start

[Nitrometano]

Hi, I have in 1979 911SC with a starting problem.

The old problem was the following: The old pick up coil fail and there is no spark from the coil. I replace it with a new one from Pelican Parts.

Now this is the problem: I install the new pick up coil. The spark only jump 1/16" (no more) from the coil-distributor cable to ground. The engine not run. The spark color is blue.

This are the info that I found:

Coil primary resistance: 0.5 ohms
Coil secondary resistance: 0.678 ohms
Pick Up Coil continuity between terminal #7 and #31d from CDI: 606 ohms
Pick Up Coil volts at terminal #7 and #31d: 0.500
CDI volt pulses: 0.045
I clean the terminals.
The CDI make a humming sound.
Good grounds in all conections (CDI ground, coil ground)
Fuel pump is working.
Battery volts are 12.45 DC
I don't find the RPM limiter in the back of the gauges to clean the connectors.
I replace the coil to distributor cable of this car and put another cable from another Porsche and the problem are the same is the same car.

The CDI can make the humming sound and only puts 0.045 volts AC at the coil cables? That means that the CDI fails? Can a new pick up coil come damage from the auto parts store? What can cause the problem.

Please help me with this problem.

Thanks,
Nitro

[Jim Smolka]

Jumper the FP sound it runs with the key switch on. This is possible at the front trunk fuses. Then, remove the air cleaner and push up on the air metering valve, it should squeak as fuel goes through the fuel distributor for a second. Then try to start the car. It should fire if there is spark

[Nitrometano]

The fuel pump also controls the spark?

[Jim Smolka]

Just trying to help. On some CIS cars, the fuel pump is activated when the car is started and air is moving through the fuel distributor assembly.

If a CIS 911 does not fire, the first thing IMHO, is to ensure that the FP is operational and gas is going into it. This accomplished by forcing the FP to run continuously. Then, giving a little squirt of gas via the fuel distributor is another quick check. They checks are very simple to do and helps to trouble shoot the systems.

[Nitrometano]

The fuel pump is ok and I heard the squeak sound of the injectors when I lift the CIS plate.

There is another test that I can make to the CDI to check if they are working properly?

[Lorenfb]

"The spark only jump 1/16" (no more) from the coil-distributor cable to ground. The engine not run. The spark color is blue."

Why are we focusing on the fuel system????????????????

A 1/16" spark doesn't get it! It should be about 1". Don't throw darts are the problem.
Or maybe it could be a bad brake adjustment keeping it from starting.

Check out this web site (www.systemsc.com) on the Diagnostics page under No-Start.

[Nitrometano]

Hi, I check the systemsc web site. Is great.

But, I want to know if there is another tests that I can make to the CDI because if the problem are the coil, why the specs of the coil that I obtained are between the correct specifications?

[Lorenfb]

You need to get a basic coil (old VW type) for testing. Don't try to measure the
CDI signal at the coil. More than likely, the CDI is O.K. Hopefully, you don't have
a silver Bosch coil (not good).

[Nitrometano]

Yes, I have the silver coil. Damn!!