Rebuild - No Start (No Spark)
 

So I've finished putting most of the car back together and am trying to start her up for the first time. Engine turned over fine, made oil pressure fairly quickly, is delivering fuel (plenty of gas smell at the tail pipe) but will not fire up.

My timing light showed no indication of spark but I'm not sure if it's the light or the lack of spark (light's a few years old and has been banged up). It was too late to do some other tests last night (like coil wire to ground) but I did test the resistances on the coil. It's showing .9-1 ohm at the secondary, and 990ohms from primary to secondary.

the part number is 0 221 121 001, and it's an '82. Looking around on the site I see that the P-S resistance should be more like 790ohms max, but could this out of spec cause a complete no spark issue, or just a weak spark? For what it's worth the timing light registered nothing at all while cranking, and at no point did the engine even hiccup like the ignition was weak or timing was off.

New cams in the engine so I'd like to limit how much test cranking I do, so welcome to ideas. :confused::confused:

Oh, the CDI buzzed just fine but I haven't checked the static voltage to it or AC voltage while cranking from the green pulse wire.

Turns out my coil mount plate was too well powder coated and not grounding the coil. Fixed that, still no spark, so I think I may have just toasted the coil now that I can see the resistances are out of range. Hopefully nothing else...

Checked for pulse, not seeing any, but the pulse wires and shielding are continuous all the way to the dizzy. Brand new harness and wires too.

My volt meter is digital, I think, will it even see a pulse?

You are gonna need a scope to check out the CDI pulse. low duty cycle won't show on Voltmeter.

You might pull #1 plug, ground to cylinder and crank locking for a spark. This will confirm your timing is roughly okay as well if it matches timing light

Good tip, thanks, I'll look out for one.

use a plug and ground it as above to verify spark and that spark is strong
where are you checking for this "pulse"
is the tach moving (never noticed if it does but curious)
is the DIST in 180 out.
plug wires correct.
did you forget to put the rotor on (yes i have done that )

is the FV vibrating
can you push down on the sensor plate and hear the injectors
remove the connector from the top rear of the AFM so you know pumps are running.
CSV wired correctly (a little fuel from pressing the sensor may help)


this is what the signal from the dist looks like.
dont remember the pulse width but a MM wont see it.

one thing i like about the MSD is that it has an LED that lets you see that it has an input. also the adjustable rev limiter

http://forums.pelicanparts.com/uploa...1664103920.jpg

Actually, that signal is an inverted input signal with respect to the ground pin of the CDI, and causes timing problems.
The proper phase of the distributor input signal is this;

http://forums.pelicanparts.com/uploa...1664126865.jpg

I didn't have a chance to check the motor again--did a lot of body assembly while waiting on a coil--but thanks for the input.

On fuel, it's definitely delivering as I get a strong odor of gas out of the tailpipe when cranking, and can hear everything working away when I lift the fuel plate.

Haha the rotor is in and the plugs are all wired properly, what I really need to do is check the line from the coil to ground to see if I get anything.

I was checking for the pulse across the pins, but saw in another thread that someone had better luck checking for pulse from the signal pin to a ground. I think the Bentley may be wrong in its directions as it shows checking pulse from signal to shielding? Not sure.

I'm confident the dizzy is in properly. I had it 180 out a few years back and even with that it would still hiccup, right now it's just dead.

yes it may be. dont remember. when you install an MSD on a 911 after 80 or the 930 you have to "flip" the signal. the CD/MSD is "suppose" to be triggered by the very steep vertical slope. if it is "upside down" it gets triggered by the slower changing signal that is curved. and whats worse when it is triggered by that part is that it actually will advance the timing as RPMs go up because it moves.

i dont remember which is which about the MSD/bosch unit. one needs the positive to neg transition to trigger, the other needs the NEG to positive transition.
i could look it up again if anyone really wants to know.

the CD sends about 400v to the coil.
i have looked at it with an Oscope but you need a high voltage probe.

i dont think you can "see" anything with a MM.

i had the same grounding issue with my coil. for some reason one of the lugs the coil plate was bolted to was not grounding, so i had to move the wire.

if you have a MM, check from continuity form the neg of coil to the CD unit.
make sure your ground strap from motor to body is connected, but i would think it would not turn over.

if i remember correctly i think there is a ground wire from that plate the CD is bolted to to the body.

verify spark with a plug, not the timing light.

ok. i looked it up. that is the pic for the signal needed for the MSD.
the MSD wants a NEG to POS transition.
bosch wants POS to NEG.

All really good info, thanks, I'll be doing some more checking tonight and report back what I can. I don't have a scope but I picked up an analog MM that might show a response, if not be totally accurate.

The distributor signal to the CDI (pin 7 & Grd) measured with a MM set to AC volts is .60 ACV while cranking. The ohm reading (not cranking) is 600 ohms.

Is the 600 ohms testing across the pins at the CDI itself or the pins in the harness?

Update, no spark at all from the main coil to distributor. Still can't see a pulse on my multimeter, digital or analog. Brand new harness and distributor connector (shielded green eye) though so I wouldn't expect them to be the culprit. Guess I'll need an oscilloscope to confirm though. ****.

Not seeing 600 ohms on any pin to pin on the CDI itself. Only 69.2 ohms from power to ground or shield wire pin. Of course 0 ohms from 31/d to 31/1. On the harness I'm showing an open circuit from 7 to 31/1.

If the pulse to shielding in the harness is reading open does that mean the wire is toast? Bad connection at the distributor?

This blows, my dudes. Even worse as every crank is one more crank on new cams. Oof.

The resistance across primary to secondary on the coil dropped down to 680 now as well. Curious.

No! The pins for the distributor pickup, i.e. the green wire going to the CDI.

Then you have a distributor pickup signal problem or a green wire problem. Don't waste time checking the coil now!!!!!!!!
The CDI won't spark without a distributor signal. Post #14 describes the test.

Okay got it, thanks!

I'll pull the distributor tomorrow to see where along the path I'm losing continuity. Any way to test the internal connections at the distributor with probes, i.e., jamming the probes in there to get 600 ohms?

Edit: of course I bought the Uro wire off eBay. I think I've finally had it with that supplier...