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Simplified steps to dx no start?

I have not been able to start my 2.7 MFI. If I remember correctly you can test to see if you are getting a spark at the plugs by pulling one of the wires and holding it near the plug and watching for a spark while someone cranks the engine.

If I don't have a spark there at that point, can I pull the coil cable from the center of the distributor and hold it close to a ground on the engine and then watch for a spark?

If I don't get a spark there, then I have a bad coil?

Does this process sound like an quick and easy way to make a diagnosis of whether I am getting spark?

I know I have fuel because I can hear the pump and I can smell it, and the engine turns over quite quickly. I haven't done anything to the car except let the car sit for 2 weeks getting ready for an oil change and brake flush. It ran fine previously.

Sounds like you are getting fuel.

If you are not having a spark, try this:

Quote:

Originally Posted by HarryD (Post 4395758)

To get a spark to the spark plug in the engine. Several things need to happen. First, you need power to the CDI. Next you need to have a way to trigger the CDI (the points do this by opening and closing). Then the CDI will then send a pulse to the coil which will increase the voltage and send it through the high tension lead to the rotor and to the selected spark plug. You need to verify that each step in this chain is working.

1) Verify that the CDI is getting power. Do you hear it wining (if it is a Bosch unit)? If so, you are good to go.

2) Verify that the CDI is producing power to make a spark. You can do this with a "telegraph" test. Take the high tension lead off of the center of the distributor and put a spark plug on it. Ground the threaded part. With your plug attached to the center lead, open the distributor, remove the rotor, place your key in the run position, and manually open and close the points. Each time you cycle, you should see a spark from the plug. If you do not, you may have a bad CDI.

3) Verify that the coil gets a signal when you crank. Replace the rotor and distributor cap. Leave the plug on the center high tension lead. Crank the engine. Do you see a spark? If so, you are getting spark to the distributor. If not, your point gap may be off or there is some other problem with the connections.

4) Verify that the spark goes to the spark plug wires. Reattach the center lead to the distributor. Attach you spark plug to one of the leads going to the cylinder spark plugs and ground. Crank engine. If you see a spark you may have a timing problem. If no spark, you have a problem with your rotor or distributor cap or your wires are improperly seated.

Do a search here as there are many threads on this topic. Look especially for the ones by early_s_man. Warren (RIP) left a great deal of knowledge on troubleshooting this problem.

This thread may be handy too: http://forums.pelicanparts.com/porsche-911-technical-forum/474952-ignition-questions.html

CDI not something I am familar with. But I can see it next to the fuse box. I noticed I have a single red wire that goes from the fuse box to the CDI unit and another wire that is heavily wraped in electrical tape. When I switch the ignition to on position and I move the red wire, I can hear a click within the coil. So this is my problem because after I move the wire and go and try to start the car, it fires up right away. So I will have to see how is this wire connected to the bottom of the CDI unit and make it more secure.
In the fuse box I noticed slots for 3 fuses. I have the top 2, but the bottom one is missing. What does this missing fuse control?
Thanks

The red wire provides power to the CDI (Capacitive Discherge Ignition) box. The Black wire goes to the points in the distributor and when grounded, causes the box to discharge it's charged up capacitor to the coil via the blue/yellow wire. There should be a 3 prong connector that connects the wires to the CDI box.

You can see the wiring here: http://www.pelicanparts.com/911/911_Parts/Electrical/911_electrical_1973_CIS_Part2.jpg. The CDI box is item 9. The distributor is item 5 and the coil is item 6.

One of the fuse slots if for the Sportomatic transmission. That is the missing one.

carful there is high voltage at the coil wires (320v+-) it will knock your you-know-what right in the dirt

Without getting too specific, all internal combustion engines require air, fuel and a spark. Each has their circuit and circuit components. It helps to know how the system works so one can diagnose the system more accurately.

Lacking that knowledge, many attempt to repair by replacement. That sometimes works, but it can also become expensive, and one winds up with a bunch of spare parts. It's also not recommended due to a typical lack of sufficient funds to replace everything.

No spark? Work backwards in that system until your diagnosis confirms a gap in the usual process. The ignition system has a mechanical as well as an electrical component. Electrically, the source is the battery; the end of the circuit is the spark to ground. There are circuit elements in-between, each dependent on the other (switches, circuit paths, CDI unit, distributor, points, etc.). A good technician should be able to assist if you don't have the patience or the time to learn it this time. Forum advice is good too if you understand the jargon and can follow and perform the suggested diagnostic, repair and confirm steps.

Sherwood

Quote:

Originally Posted by James Brown (Post 7401570)

carful there is high voltage at the coil wires (320v+-) it will knock your you-know-what right in the dirt

How do I protect against accidental shock? Can I discharge the system, before installing the wire?

Quote:

Originally Posted by bcgreen (Post 7402776)

How do I protect against accidental shock? Can I discharge the system, before installing the wire?

Don't hold/grab any high voltage wires (coil, spark plug cables) while the ignition system is ON or while cranking engine. The wire insulation may not be up to snuff.

Sherwood

Simple enough. I just want to replace the one wire, so I find no need to turn ignition on or crank the engine.
Thanks