Need help, no spark on 70T.

[hotdogwater]

I am trying to start this 1970 911 T that sat for many years(14+). I replaced all the fuel components and rebuilt the carbs and now tackling the ignition system. I have no spark and trying to figure out how to resolve without throwing parts at it. Just a note, you can't search for the term "no" on pelican so this one was hard to research so if there are some good old no spark procedure/forum posts please point me to them.

- can hear hum(more like whine to me) from CDI but reading on PP forums this does not guarantee the CDI is good
- I get no 12v+ at the coil with ignition on
- replaced coil even though I have no 12V+ at the coil
- Car has a Marelli distributor so I was going to swap out for Bosch and electronic ignition but found the parts for the marelli for a reasonable price (not my issue but might impact overall resolution I though)

I was going to swap for Bosch and use Pertronix but I didnt pay close enough attention to the part numbers and ended up with a Bosch dizzy for a 2.4L engine (again prob not related to current issue). So without throwing parts at it, can I put my meter on the CDI and determine if it's functioning?
Recommendations to fix the issue and provide reliability (replace Marelli with Bosch and electronic ignition?)

Thanks in advance for any advice.
-Daryl

[jcambo7]

Have you checked the gap on the points? Did you make sure the distributor was installed at top dead center?

[BK911]

+1 for points.
Clean contact surface and verify gap.
Then set timing.

[Trackrash]

Originally Posted by jcambo7

Have you checked the gap on the points? Did you make sure the distributor was installed at top dead center?

Check the points.

You will not get 12 volts at the coil. You will get 12 volts at the points. Be careful, it is more like 300 v at the coil.

Since your CD box is making noise, I assume it is getting power.

Take the center coil wire and place the end next (1/ 8") to the motor to check for spark. Remove the cap and rotor from the distributor. With the ignition on manually operate the points and check for spark from the coil.

[hotdogwater]

Originally Posted by Trackrash

Check the points.

You will not get 12 volts at the coil. You will get 12 volts at the points. Be careful, it is more like 300 v at the coil.

Since your CD box is making noise, I assume it is getting power.

Take the center coil wire and place the end next (1/ 8") to the motor to check for spark. Remove the cap and rotor from the distributor. With the ignition on manually operate the points and check for spark from the coil.

I tried the coil plug wire near ground and got nothing. Also pulled a plug and wire and held it up to ground and got nothing there as well.

I just pulled the dizzy cap and rotated the engine by hand and see points moving but not very far, the gap is almost not noticeable. There is 12v+ on the arm of the points and ground on the base. The 12v+ seems to be cutting in and out as my probe chirps like a bad connection almost (registering 12v on and off and on and off. etc...etc..)
With the wire coming from the coil 1/8 in from ground on fan I moved the points arm as far as I could and got no spark on coil. (not sure I did that all right)

[jcambo7]

The gap for the points should be at 0.12 if I remember correctly and I've read that people put it at 0.14 too. I wasn't getting spark on my 2.2t either until I adjusted the points to 0.12.

[horizontallyopp]

Odd problem that bit me recently on a Marelli - check that the center pin in the distributor cap that is supposed to float on the rotor isn't pushed in and stock and no longer making contact with the rotor.

[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.

[T77911S]

if the points are opening and closing and you are verifying this with your probe.
as the dist rotates the 12v will drop in and out as the points open and close.
you have replaced the coil
then it looks like the CD unit is bad.

the large capacitor inside the CD is probably bad.

if you have a MM and want to open the CD and test the cap here is how.

set the meter ohms and on a low scale.
connect one lead to A on the input to the CD.
connect the other lead to "4" (CS/thya) on the right side of the diagram.

the meter should either increase or decrease,
swap the leads
the meter may increase or decrease.
it should not be a sudden change.

if the meter shows either very hi resistance or a short (it may not move), the Cap is bad.

[hotdogwater]

Thanks guys, I'm going to try some of this tonight and see what I get. Any recommendations on where to get the CDI or rebuild it? Would a Permatune CDI be just a good at half the cost?

[T77911S]

someone here rebuilds them.
if it is for the 70 I would rebuild it.
if you want to go another route get the MSD and Msd coil

[HarryD]

Our host offers the service to rebuild the CDI unit. This is the link: Bosch CDI Repair Service ** CUSTOMER MUST SEND THEIR CDI UNIT IN FOR REPAIR ** ATCDIREPAIR - AT-CDIREPAIR | Pelican Parts

[reachme]

+1 on read up on the earlier threads on this. Before jumping right to rebuild the CDI-the most expensive part of this, there are many ways to unit test each component and dispell the magic behind how this works. I hope to walk you through that. sorry if I am confusing or you already have a grip on this.

Here are some things to consider testing first:
Disconnect that fat plug below CDI and check for actual 12V to CDI

Disconnect battery!
Then check for good CDI ground with ohmmeter (bad grounding happens). I believe it grounds to where I have disconnected this ribbon cable for cleaning


check CDI to distributor for resistance
Check CDI to coil for resistance
Check good coil to ground (brown curly wire)


Once the basic stuff is done then the fun:
Battery reconnect:
You have 12V to the CDI and get the whine, that is good:
See that black wire that plugs into the bottom of the distributor? Inspect it because they both corrode and beg for mouse chewing. As distributor turns that wire goes on and off ground and triggers the CDI to fire. unplug that and put a whistling probe tester tip touching that and clip the "ground" to the distributor (where it would have plugged in). That puts the whistling tester in line between between the CDI box and the distributor to test for trigger.
Now rotate the crankshaft clockwise by hand (not the bolt in the middle of the fan, the hard to reach one below that) and you should hear the whistle turn on/off as it rotates. If so that means your distributor trigger is OK. You can measure voltage when it goes high or assume you are good here. My video of this are too big to upload.

Next unplug the coil completely and do a resistance test with said ohmmeter. I had trouble finding what resistance should be, also what is good/bad range but I skipped this because I bought a new one after searching for 20 minutes. be smarter than me and look up proper value.



since cable to center of coil is already unplugged, unplug distributor side and check resistance of coil to distributor cable with ohmmeter. It should offer little resistance


So we have 12V, we have trigger, coil, cables all good. plug black trigger wire back into distributor and do simple test for spark. First disconnect battery. Then connect the one side of that cable back into the coil center. The other side connect to the tip of a known good single spark plug and clamp somehow. Then ground the spark plug threads with an alligator clip or old wire like I did. Then let go and make sure it stays connected (dont hold the spark plug). set this test up with battery disconnected since that coil wants to kill you!

Once you no longer need to touch it, reconnect battery, turn key to 1st position, hear CD whine and turn the engine crankshaft by hand (or have assistant turn the key and run engine). You should see that spark plug firing several times per revolution.
Regardless of test result disconnect battery next -to undo this setup (remember coil wants to kill you and assume assistant is in cahoots with the coil)

If it does not fire get a new coil first, they are like $30 and test again. If still not get CDI rebuilt.
If it does fire get new spark plug wires (cheapest). then distributor cap (still get those for Marelli?) if still doesn't work rebuild distributor.

I hope this helps and applies to your year, I did not have Marelli and had a 71. This recollection is from top of my head from a few years ago.

[hotdogwater]

Wow, thanks for all this detail and write up reachme, can't thank you enough. My knowledge of electrical stuff is limited, please excuse my ignorance. I don't know that my meter has the chirp mode so I used the power probe I just bought. It displays ground or 12v+ and it's doing something weird on the inline test you proposed. When the CDI is connected it switches back and forth between ground/and 12+ over and over without moving engine or starter. I made a video to show what I am talking about.
So with ignition on, the CDI to dizzy wire is chirping (showing 12v+ on and off) but not ground signal. The other weird thing is the 2nd fuse in the engine compartment (dosen't appear to be connected on both sides of the fuse block either) has this same intermittent 12+ signal. The meter shows 12+ continuous and the fuse above doesn't have this chirping 12v+ signal. At the end of the video I unplug the CDI and the modulating 12v+ stops on that 2nd fuse down.
https://www.youtube.com/watch?v=GyP1zfW9P3Y <-- probe test video

Guess it's time to pull CDI and try some of the tests that T77911S (TY for posting) before I replace/rebuild.

[reachme]

Use the probe only as a quick test for power, then a voltmeter/ohmmeter for accuracy/consistency of signal. You are doing the opposite, don't expect consistency from the probe chirping.

With voltmeter inline and key at position 1, turn the engine clockwise like it says above and you should see that 12v on the voltmeter go to 0, then back to 12v as the engine keeps turning.

See as you turn the engine you also turn the distributor. When the distributor is lined up it signals the CDI on that wire you are seeing 12v. The CDI then begins sending power to the coil. The coil multiplies that which goes shooting out of the coil, into the center of the distributor which distributes it to the correct wire leading to a spark plug which sparks at exactly the right time in the cycle for ignition on that cylinder.

What you want to do is force a state change on that trigger line to make sure CDI is getting the trigger. That is CDI's input

If that is OK then test CDI output. CDI->coil->distributor->sparkplug connection.

Put the probe down, it's confusing

Good luck!

[hotdogwater]

So the saga continues.

I hooked the meter up (inline with red on wire from CDI and black on CDI connection on distributor. I get a 4-5volt reading at first that drops to under 3v. Then as I rotate the engine the voltage drops to .184 or something until the points close and back to 2.2V. Battery was just charged up.

I did find the cap, rotor, points and condenser and they are on the way so hope to eliminate those as issues. Car has original parts is seems to time to replace these 40 year old parts anyhow.

https://www.youtube.com/watch?v=ZnC7UtGrZi0

[911T70]

Originally Posted by hotdogwater

So the saga continues.

I hooked the meter up (inline with red on wire from CDI and black on CDI connection on distributor. I get a 4-5volt reading at first that drops to under 3v. Then as I rotate the engine the voltage drops to .184 or something until the points close and back to 2.2V. Battery was just charged up.

I did find the cap, rotor, points and condenser and they are on the way so hope to eliminate those as issues. Car has original parts is seems to time to replace these 40 year old parts anyhow.

https://www.youtube.com/watch?v=ZnC7UtGrZi0

You should measure voltage referenced to ground; they way you did it, the measurement was referenced to the input of the CDI. Reconnect everything, connect the negative lead of the voltmeter to a good ground and clip the positive lead of the voltmeter to where the red wire connects to the distributor.

[hotdogwater]

Originally Posted by 911T70

You should measure voltage referenced to ground; they way you did it, the measurement was referenced to the input of the CDI. Reconnect everything, connect the negative lead of the voltmeter to a good ground and clip the positive lead of the voltmeter to where the red wire connects to the distributor.

I tried this as well. I didn't see any change in voltage with the meter grounded and hooked to CDI wire (with wire connected to distributor or not connected). The voltage was same 12v as I rotated the engine.

The new cap,rotor and points are here today so I will install those. One weird thing, the kit came with a condenser but the one on my car doesn't have a condenser installed that I can see. (it should be attached to side of distributor like most I assume)

[hotdogwater]

Well one issue solved, on to the next one. I have spark now, replaced the points cap and rotor. Pretty sure it was points not opening enough or something.

Did the static timing, hooked the fuel pump back up and tried to start it. Got some pops and sounds like she wants to start but fuel leaks made me quit trying to start it and now pulling the carbs again. I just rebuilt these zenith carbs and both are leaking fuel from an accelerator pump it appears. The carb rebuild kits were horrible.

Thanks again to everyone who chimed in to help. I am going start something and offer a small gift to someone on these sorts of threads that offer to help. I think this thread had two winners so if reachme and T77911S will send me a PM with a good shipping address I would like to send a small gift of appreciation.

Anyone know where to get a good rebuild kit for Zenith carbs?

[doswald]

Glad to see you've got spark! Try Alfa1750 on eBay for zenith rebuild kits and carb parts-great service.

dho