Need Help diagnosing no-spark

[cfassett]

I'm working on getting the engine to fire on the 77 911. Car has been idle since mid-90s. Cap, rotor, wires, plugs and coil (MSD) have all been replaced. I've also quickly gone through the ground and fuse connections and cleaned those. Fuel lines and pump are also new. The car turns over freely.

I'm getting no spark, except sometimes a single spark when the key is turned to "on" position. No noise coming from the ignition box.

Trying to determine of this is an issue with the Perma-tune 11-75 ignition, wiring or grounding.
I'm not well versed in electrical. and in need of help.

How do I determine if the Perma-tune unit is any good? Or if it's a wiring problem?

[cfassett]

Anyone?

[Walter_Middie]

A 3-pin box can be tested fairly simply; remove the 3-pin connector and run individual wires to it. Pin B (center) is +12 volts, Run a wire from pin A to the coil (the other side of the coil is GND) and then hook a wire to pin C. Connect a spark plug to the output wire of the coil via a high voltage cable and ground the spark plug.

Once you provide +12 volts to pin B of the box you should hear the 3kHz whining noise. Once you touch the wire from pin C to GND you should see a spark being generated.

[cfassett]

Are you saying to leave the wires/ plug disconnected from the box? If so, this is to bypass the ignition box?

[Walter_Middie]

Yes - unplug the box. This is a test to see if the ignition box is working.

Do you still have points? Have you checked your points gap?

[cfassett]

Thanks! Will give it a try.

This is a 77, which I believe is the first year without points.

[Paulporsche]

77s are the last year with points. S model, 2.7L, green shroud.

[cfassett]

That's what it is. I'm sure the points will need to be adjusted in this case. Obviously I had the cap off, but didnt recall what I saw in there.

On the other hand, I've gotten no spark on the inbound wire to the coil.

[Walter_Middie]

On the other hand, I've gotten no spark on the inbound wire to the coil.

Pin "C" on your ignition box needs to be grounded for you to get spark. This won't happen if the points are not working correctly. You can ground pin "C" to see if the ignition box is working - but I bet your points are corroded and not making a good ground when they close.

[cfassett]

That's good info! Thanks for the guidance. If that turns out to be the case, It would have taken me forever to find it on my own.

Hopefully I can steal some time to tear into it tomorrow and see what the situation is.

[HarryD]

Lots of threads on this topic. Do a search. Here is one thread that may be helpful.

How do i check a coil with a timing light??

Originally Posted by HarryD

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.

[cfassett]

Points, check. Corrosion, check.

[Paulporsche]

I've never seen a set of points looking quite like those! You should clean out that distributor, make sure you can turn the shaft by hand and have it spring back on its own, drop some oil down onto the wick down in the shaft, and reinstall some new points set to a 38 degree dwell.

[cfassett]

What kind of oil should be used?

[HarryD]

Originally Posted by cfassett

What kind of oil should be used?

A light oil like 3 in 1 oil.

[Targalid]

I would remove that distributor, carefully blocking the hole in the engine with a clean rag, and give it a good cleaning. If it looks corroded where you can see it, you can only imagine what is below the advance plate. I did this with mine and was amazed at how much crud came out the bottom. You do not necessarily need to disassemble it to clean it. Various cleaning sprays are available that you can direct into the cavity and watch the dirt flow out. You can check your work by seeing the action of the advance plate improve. You can also soak the entire unit in a container of solvent if you remove it from the engine.

[gomezoneill]

That trigger wire going to the dist. looks like it's taped up. Does not look good.

[cfassett]

I agree. They were actually both bare and touching. Hence the tape. When I get the chance to dig into this, unless I go ahead and buy the MSD ignition, there will be some rewiring in this area.

[gomezoneill]

Check closely the connection at the dist where the post goes through the dist housing. Make sure the insulated parts are sound.