1976 911 2.7 dizzy curve for 123 Tune 6

[47silver]

That seems logical and easy to nake that mistake.
Make sure #1,is at tdc on compression stroke. Then pull out the distributor, reinstall with rotor pointing to #1. Should start.
Clean around the distributor before you pull it with a magnet and rags , cover the hole when you remove it. If you don’t chances are you will drop a nut or washer into the distributor hole.

[icarp]

Originally Posted by SunburntLobster

So i popped all plugs out and checked the timing mark, I lined up Z1 expecting the rotor arm to point to plug 1 but it points to 2!
I tried 360 to see if it aligned with 4 but it lined up with 5.
Is my logic correct the PO may have got the timing 1 out and tried to compensate with 20deg of advance on the 123?

SBL, sounds like a good place to start. Once the car i idling it is important to set the 123
internal curve to 0* through 3000rpm, that way you know that you can't make a mistake setting the distributor to TDC and 0*, then put a timing light on the pulley, you must then turn the distributor to match the Z1 mark to TDC, now you know the timing is correct . 0* on the crank and 0* in the distributor . Now you can set the curve that i suggested or any other . I know my curve is a great starting point . The rotor info is very important as well.
Ian

[SunburntLobster]

So i set the 123 by disconnecting the plug to the MSD (the black wire connects to white MSD) and in doing so noticed both loop wires are in place! According to MSD manual one should be snipped for 6 cyl?

[Jonny H]

Please re read my post. You must confirm that the 123 is the ONLY device with a map.

Btw, if the MSD was set to 4 cylinders, effectively you’d be higher up the map ( at 4K you’d have the settings for 6k). If a limiter is set then this would come in early too. This may not matter if the MSD is not running a map.

That’s another reason why you have to know what devices have a map....

[SunburntLobster]

Hi the megasquirt is a basic fuel only with no ignition map. The MSD also doesn't have map it is triggered by the 123 using the point style connection (black wire from 123 / white wire MSD)
I have messaged the MSD helpline.
Uncut MSD loops results in 8 cylinder setting. Cut 1 loop for 6 and both for 4cyl.
Hopefully this is part of the issue!

[Jonny H]

=Hopefully this is part of the issue!

Doubt it. Usually if there is no map the box is just firing the spark as a soon as it sees the trigger. In this ‘mode’, It doesn’t care what the RPM is. Number of cylinders is used to calculate RPM which is used for maps and rev limit.

What is your total advance measured off the timing light?

[icarp]

SBL, you are in good hands with Jonny H.
I'll watch from the side lines
Ian

[icarp]

Just thinking, Do you have the correct MSD coil?
Do you have the correct plug wires for an MSD?
Is the grounding correct for the MSD ?
in these last few posts I have the Idea that you did not set this system up and any part could have been improperly installed , am I correct? I think I would go over EVERY SINGLE STEP,
FOR FOR SET UP, FOR EACH AND EVERY PART NOT PORSCHE
just trying to get you to a fun running car
Ian

[Mr Beau]

Isn't this all easily verifiable by disabling the vacuum advance and revving the engine? Set the curve to 10 degrees everywhere and make sure it doesn't move. Then adjust and test.

[SunburntLobster]

So I set the TDC (Z1 line up with fan housing notch and confirmed rotor arm pointing to #1) rotated body of dizzy until the green LED did it's thing, installed new diz cap and arm, new plugs but get no spark so I reinstalled old cap and arm still no spark.

The MSD box LED all indicate no fault and light on each 'fire' which is showing the 123 is at least triggering it.

I wonder if my coil is incorrect and stopped working, it should be a 1.5OHM however is a MSD blaster which is only 0.7OHM

All part of the fun!

longterm plan will be to ditch the 123 diz and MSD AL6 and look to get my Megasquirt 1 modified to work with a Ford EDIS-6 and trigger wheel.

[SunburntLobster]

I heard back from the MSD helpline and one of the loops should indeed be cut, whether it makes a difference I don't know but has made me check all of the previous installations.

I am currently researching the EDIS-6 which seems a reasonable option.

[47silver]

get an old spark plug
take off the coil wire that goes to the distributor and connect it to the spark plug
ground the plug from the threads to a good ground.
have someone turn the key and see if you have spark.
if you do
get a timing light
connect it to number 1
have someone turn the key and see if the light is close to the timing marks.

[SunburntLobster]

Thanks tried that last night, I have ordered a new coil with the correct ohm rating, wasn't expensive and would have needed doing eventually! Hopefully the old one was failing hence the misfiring that got progressively worse.

[icarp]

The OHM rating is very important , coils must be paired to ignition systems .
keep at it
Check everything
Ian

[SunburntLobster]

Thanks to every one who contributed, especially Ian and Jonnie. She now runs like a champ! Went back to basics and reset everything and stuck new coil in. Super pleased to have sorted it and learning along the way!

[mysocal911]

Originally Posted by icarp

The OHM rating is very important , coils must be paired to ignition systems .
keep at it
Check everything
Ian

Actually, the resistance, "OHM rating", of the coil primary of a CDI (capacitive discharge ignition) is essentially of no concern versus an (IDI) inductive discharge ignition system.
With a CDI system, energy is just transferred to the coil, versus an IDI system where spark energy is developed based on the primary resistance and inductance.

[icarp]

Originally Posted by mysocal911

Actually, the resistance, "OHM rating", of the coil primary of a CDI (capacitive discharge ignition) is essentially of no concern versus an (IDI) inductive discharge ignition system.
With a CDI system, energy is just transferred to the coil, versus an IDI system where spark energy is developed based on the primary resistance and inductance.

He is running an MSD box , if the coil is not matched , the coil will burn out prematurely.

There are many nuances to high power ignition systems . Matching to OEM specs is important .
Ian

[mysocal911]

Originally Posted by icarp

He is running an MSD box , if the coil is not matched , the coil will burn out prematurely.

There are many nuances to high power ignition systems . Matching to OEM specs is important .
Ian

Really? Like what is high power? Provide detailed info. Just because the MSD provides multiple sparks that end at about 2500 RPM,
doesn't qualify as "high power".

Read here about "high power"; The MSD Ignition - 'Exposed'

[mysocal911]

Here are parameters from various coils being used by Porsche owners;



Found here; https://www.systemsc.com/diagnostic.htm

As can be seen from the parameters of the Bosch TCI coil (inductive discharge - 911 black/silver) and the MSD coils, they are very similar.

[icarp]

Sent to me from Sunburntlobster,
Hi Ian,
Yes it was mainly a knackered coil, the MSD didn't have the loop clipped for 6 cylinder and the diz needed reindexing and curve map bringing back to standard. Also the earth point was really poor which was causing intermittent issues with the MSD and Megasquirt controller!
New plugs and she is running strong and sounding great!
Thanks for all your help.

We are all happy for your success
Ian