MSD in a GTD

I'm in the process of installing an MSD 6AL in my GTD.
Im a bit confused with the wiring that wnt to the + side of the coil. There are three wires, a white, a white with a grey stripe and a white with a yellow stripe. When the ignition's on, I have 12v at the white wire and white and yellow wire but not at the white and grey wire. The white and grey gets 12v when the ign is switched to the start position only.
Now I understand that the white/grey wire bypasses the ballast reiston to give a full 12v to the coil on start up but the MSD does not need this. What do I do, and where do I wire the tacho to?
Any advice gratefully received.
Thanks
Simon

Hi Simon -

From the MSD:-

Thick BLACK to Chassis Ground. (Good Earth is important)

Thick RED to Permanent +12V eg back of Alternator (Do NOT use a fuse - the MSD is internally protected and another fuse will introduce a resistance into the circuit)

The thin RED is then used to switch the MSD on when +12v is applied to it - so connect to the switched +12v that normally goes to coil.

The long ORANGE and BLACK pair connect to the coil (Blaster2?) - and as they can have SEVERAL HUNDRED VOLTS! between them - DO NOT TOUCH or CONNECT ANYTHING else to coil terminals.

There is a Tacho output (recessed Spade connector) on the end of the MSD unit which may drive your tacho providing it is of the correct type. If not, MSD sell a Tach adapter (8820 ? i think) that should sort it.

To trigger the unit, i.e. timing, EITHER a magnetic input can be connected to the MSD via the PURPLE and GREEN pair, OR, the WHITE wire can be used to fire the MSD and can be grounded via normal points (although I suspect your MSD distributor will probably have a magnetic output). Do NOT connect the white if you use the MAG input pair - but grounding the white can be used to test-fire the coil to test spark from coil 'king-lead'.

Hope the above makes sense and is useful.

regards

Thanks Paul,

The problem I'm having is with the GTD end of the wiring.
I presumed I would find a switched 12v from the ignition which I would connect to the red MSD wire and another that was connected to the tacho. However, I wasn't expecting the tacho wire to have switched 12v running through it. Is that right? If so, is it ok to connect the switched 12v tacho wire, to the tacho out on the MSD? /ubbthreads/images/graemlins/confused.gif

Thanks
Simon

NO NO NO NO, you will just burn the MSD out. Identify the wires from the GTD loom, white is live feed from ignition switch, white/yellow is the Ballast resistor wiring, white/silver is the rev counter feed. Connect the white/silver to the recessed terminal in the MSD, but even then the rev counter still may not work, there are two types of instrument, only one will work with the MSD, junk the white/yellow wires - do not connect them anywhere, and use the switched live feed white wire to feed the smaller of the two red msd wires.

Thanks Frank,

I have isolated the white/yellow that originally went to the ballast resistor and disconnected/isolated it from the rear of the started. I have the white ignition feed that gives 12v when the ignition is on, but the white/silver rev counter feed also gives 12v when the ignition is switched on. I understand the instruments have to be powered, but is it ok for 12v to be coming down this line and do I connect the tach feed to this?

Simon

Simon,

On GTD wiring there can be a White/Slate (white/grey) and/or a White/Black wire used for the tacho. If you have the white/slate then disconnect it from the back of the tacho and check that you no longer have 12v where it arrives near to the coil. If the white/slate is only connected to the tacho input then it shouldn't affect the MSD. It might show +12V but this will be as it will have a fairly high resistive 'pull-up' within the tacho itself.

Having said all that the tacho may not work as there are at least two different types. The voltage detection ones should work with the MSD but current sensing ones may not. I have a Smiths (Caerbont) with my MSD and that works fine.

Anyway I hope I haven't confused you further!

Simon
I'm looking into MSD ignitions as well at the moment. MSD's website seems full of info. There is a huge forum and also a download section with what appears to be instructions and wiring diagrams for everything.

Website is
msd website

I have a crank trigger with two wires coming off it and a distributor which has no wires. I guess the advance on the dizzy is locked or it hasn't got one, so I'm looking for a system incorporating rev limit and retard system. MSD 6 Digital with Blaster 3 coil looks favourite currently.

Edited to add website address

The Tach used on my GTD is a Steward Warner. If your's has SW on it anywhere then thats what it is. Attach the output from the tach to the input on the end of the MSD box. Do not attach anything else to the MSD tach input. The small red wire needs to have 12v's attached to it whenever you want the car to run. There is both a start and run post on the key switch. Poke around the key switch with a meter and find the post that has 12v on it all the time once the key is turned on. Don't worry about the start posiston with a MSD setup. Ground the black wire to the neg - post of the battery and run the big red wire to the pos. + post of the battery. I needed to lengten both of these wires on my car.

If you use a MSD distributor then plug the cable into it and the other end into the MSD box.

Also if you leave out a rev chip everything will work but the MSD unit will not limit revs.

If you need help send me a PM and I'll give you my phone number and we can chat.

OK, heres a picture of the back of the tacho, which shows the white tacho wire going to the + side of the coil!!! Now I know I don't connect it to the coil, it goes in the tacho output of the MSD, but I just want to check this is ABSOLUTELY right. (not the coil/MSD end but the tacho end)

Run the white wire to the spade conector on the end of the MSD box. Do not hook it (white wire) up to anything else or hook anything else to the spade connector on the MSD box. If it works then cool then your are done. If the tach does not work then you will need a MSD tach converter. You will not hurt either the tach or the MSD box by trying this.

If you want to, post a picture of the front of the tach I'll confirm that you have the same tach as mine. My tach worked first time without drama hooked up with white wire to spade connector on MSD box.

Simon, do not get confused, the white from the rev counter connects to white/silver ( or grey depending on your colour vision ) and this wire connects to the msd rev counter output ( NOT the switched live white which is adjacent to the MSD unit, this one is connected to the small red wire into the unit ) Frank

OK, here we go....
The MSD wors fine, car runs well (tach wire disconnected, tach not working)
I got the MSD PN 8920 tach adaptor and connected it up and started the car, not only did the tacho still not work, but the car would not turn off!
Despite checking that the +12v wire fron the ignition is switched (I have checked with a test meter that it turns on and off with the key ok) to stop the car I have to physically pull the wires apart! Its as if its dragging 12v down the wire when its running.....what on earth causes that!!
If I disconnect the tach adapter and go back to how it was, it still runs on (although slightly stumbling as if the voltage has been reduced)
Have I busted the MSD unit?
Do you get the feeling you should have never started something? /ubbthreads/images/graemlins/confused.gif

Simon,
Have you downloaded MSD's installation booklet from their site, it covers areas like that.

Brett

I have all the instructions and I think I either need a diode to the charging light and/or a resistor to the red wire on the MSD. It seems there may be a small amount of "leakage" that's keeping the unit firing.
Any ideas what size resistor I would need?
Simon

OK, Sorted the diode and it's fine now. Still can't get the tacho to work though.
Simon

Here's a couple of things to check.

1. Is there 12VDC being applied to the tach? Check with meter when engine is running. Is the light on in the tach? Is the 12vdc sorce coming from the dash light circuit? It should not be. Its sorce should be on when the engine is in the run mode, not the start only mode.

2. Does the ground wire that comes out of the tach really go to ground? This wire should always be grounded, Check with meter. This should be zero ohms.

3. If 1 and 2 are ok, then run a wire, not the one in the car wire bundle, but a seperate wire from the tach input wire comimg out of the tach to the spadelug on the MSD Tach output.
Note: If the type of tach you have needs a tach adapter then this will not hurt anything it just will not work.

4. If 3 does not work then attach the wire from the tach in 3 to the tach adapter input and use the tach adapter as normal. If it works either way now then you are using the wrong wire in the bundle for the tach signal lead.

5. If none of this works then borrow a tach and hook it up outside the car and see if you can make it work.

6. If it does not work, there is special test equip made for MSD units that check them out. Ask around your area and see if you can get the MSD box checked out.

Lastly the MSD paperwork says to run seperate 12vdc and ground wires directly from the battery posts to the MSD unit. Anything else is just one more thing to troubleshoot when it does not work. This could be the cause of some of your earlier problem. If the car runs badly then try this.

Thanks Howard, I'll work my way through your checklist in the morning and let you know how it goes.
Simon

Simon,
Europa Spares do a MSD Tacho conversion piece of kit. I don't know if its on their website, but its in their catalogue.

Brett

Simon,

It'll be appreciated if you could share your findings w/ me as I intend to replace current ditributors/iginition control/coils w/ MSD products later? /ubbthreads/images/graemlins/tongue.gif

Thanks

Hi Yuji,

The MSD was easy to install, very simple and works fine, it's the tacho that's causing me the headaches. I'll let you know how it goes.
Simon