| Author | Message | ||
| Gerrit Visser (Gerritv)
Junior Member Username: Gerritv Post Number: 175 Registered: 6-2001 |
Hi Dom, My car is Euro, 1976. The unused wires in the photos are for R1/R2 points from a relay in footwell and those extra ones near the coils are the Start relay wires, to bypass ballast resistors on startup. (more spark). Neither are in use altough I will be fixing things so the wiring looks as if it is connected. | ||
| Dom Vitarella (Dom)
Junior Member Username: Dom Post Number: 111 Registered: 11-2002 |
Success! I installed the MSD 8910 tach adapter last night, and connected the black "mystery" wire to the MSD as per the directions, and Voila! everything seems to be working. With a warm engine, my tach reads just below 1000 rpm at idle, and about 3500 RPM in 5th gear at 60 MPH. Gerrit, thanks for the photos. But, my wiring seems to be slightly different than yours. I'll have to look and take some more photos. Is yours a Euro model? At least for now my tach seems to be working. Dom | ||
| Gerrit Visser (Gerritv)
Junior Member Username: Gerritv Post Number: 172 Registered: 6-2001 |
The wire near the tank, coming out of firewall' is for the second set of points bypass relay. Tach wire should come out of bundle near the rear most coil. Brown, although diagrams say brown/black. Last picture shows harness where the sub harness comes from. The subharness you want is the one running across the bolt to right of RH coil.    | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 974 Registered: 4-2002 |
I'm going to hook one lead of an ohm meter to the "Mystery Wire" and poke around with the other lead to see if it is connected to anything. There are two black wires leaving the triggered side of one of my coils, while the other coil only has one such wire. I'm assuming that the extra wire on that coil is for the tach. Would make sense, but....... | ||
| Dom Vitarella (Dom)
Junior Member Username: Dom Post Number: 110 Registered: 11-2002 |
Hans, MSD tech support told me not to attach the tach wire to the coil, but to the white wire of the MSD unit. The MSD installation manual also states that there should only be 2 wires attached to the coil, 1 orange and 1 black which both lead to the MSD unit. Perhaps the MSD coil voltage is incompatible with tach? When I get my tach adapter tonight, I will try what MSD recommends. i.e., tach wire spliced into the white wire of the MSD system. The white wire in the MSD unit goes from the MSD unit to the distributer. The tach adapter is also spliced into that white wire. Hopefully all will work and I will be in happy land... Dom | ||
| Dom Vitarella (Dom)
Junior Member Username: Dom Post Number: 109 Registered: 11-2002 |
Peter, the wire in the bottom photo is blueish (azure)in color with a black stripe. It has a black covering over it, though. If the back wire in the back is also for the distributor points, then why is the tach working when I connect it to the MSD tach output? If, as Hans suggested, that this wire is connected to the tach wire, then somewhere along the line I should be able to find where the tach wire is spliced into this one. I'm going to have to do more searching I guess. Presumably, though, it should be OK to run the tach through this wire? I'll be picking up my tach adapter after work today, and will see if I get a chance to install it tonight. I'm really looking forward to having a functioning tach. It seems like nothing is easy on these cars. But, little by little, I feel like I'm picking up tons of knowledge. Maybe in a few years I'll have a Ph.D. in the Ferrari Dino 308 GT4! Dom | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 970 Registered: 4-2002 |
Steve/Peter: My wiring diagram shows an "MN" color code, but the letters are in such an ambiguous place that I really would not place bets that it is meant to label the tach wire. My tach wire *might* be black. | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 969 Registered: 4-2002 |
Boy, you've got me really puzzled. The "Mystery Wire" that you photo'd is identical to mine. In my case, it was tucked behind the gas tank and was not noticeable until I pulled it out. "Eye"-type connector. I still think it goes up in that soft rubber conduit toward the back of the car - in the area of the coils perhaps. I can't find what might be the other end of the wire to try and hit it with an ohm meter for continuity. Here's a guess: The tach is connected to this wire at the coil end. It doesn't go directly to the tach. This looks like how my car is set up, as there are two black wires hooked together at the coil. One is probably the "Mystery Wire", the other is the tach. In your case, these two black wires are probably hanging around loose somewhere. Your other "Mystery Wire" probably corresponds in function to the firewall "Mystery Wire". It may have gone into the rear distributor, hooking up to the points. Re: Tach - I wonder if you still couldn't use the connection on the coil itself, as in the stock configuration. However, I'm using the older Crane ignition (XR700??) that probably uses voltage/current levels that are similar to OEM, as I still have the original coils. Your system might use higher voltage levels. Perhaps a resistor in the circuit would be appropriate? | ||
| '75 308 GT4 (Peter)
Advanced Member Username: Peter Post Number: 2596 Registered: 12-2000 |
Ooops, you beat me to it Steve!  | ||
| '75 308 GT4 (Peter)
Advanced Member Username: Peter Post Number: 2595 Registered: 12-2000 |
That my friend are the stock wires for the points, that run in the harness (the front distributor points wire is black and is on the firewall and the rear, near the heater and brake-booster hoses, is "azure" with a black stripe). I'm not sure how it is on your car, but I think the MSD units would have their own wires to operate from the points. Yes, as Hans said, the stock tach wire is brown (I didn't notice, but the manual calls it a brown w. black stripe wire. All I remember seeing is brown...) and is a part of the harness that runs (or ran, since your car has been modified) by the coils. It needs to be hooked up to the ballast resistor of the 1-4 coil. | ||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1527 Registered: 1-2001 |
Dom -- Seems like you've got it figured out, but I just wanted to let you know that the "tach wire" on the 308 carb schematics I've seen is color-coded "MN" (brown/black) not "M" (brown) so depending on the shade of brown it could appear all black. | ||
| Dom Vitarella (Dom)
Junior Member Username: Dom Post Number: 108 Registered: 11-2002 |
OK, I decided to get brave and try some experimenting. The MSD unit has a tach output, and what I did was attach a wire from the tach output to the mystery wire. When I did that, nothing appeared to happen at the tach. BUT, when I hit the accelerator, the tach started moving!!! So, it appears that the mystery wire is the tach wire in my car. I'm guessing it was reading about 1/2 of actual readings. Why, I don't know, but hope the tach adaper will fix it. I tried hooking the tach wire to the white MSD wire, and got nothing. Hopefully, the tach adapter should fix this, as this is the recommended setup from MSD. This is a photo of the wire:  Incidentaly, Hans, I did some more searching, and hidden underneath some hoses was the following unhooked wire. I have no idea what it is.  Dom | ||
| Dom Vitarella (Dom)
Junior Member Username: Dom Post Number: 107 Registered: 11-2002 |
Hans, If that's the case, then mine should be disconnected at both ends. My coils were replaced with the MSD Blaster coils, and have only 2 wires going to them, which lead to the MSD 6A unit. The wire I have appears to be going into the firewall. That's why I thought it may be coming from the tach. I'll try to take a couple of photos tonight. Dom | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 968 Registered: 4-2002 |
Dom: I *think* I figured out the "Mystery Wire". It's probably the wire that runs from the points to the coil in the original setup. It's just the right length to go into the front distributor. I suppose it's remotely possible that the wire is still connected to the coil, but I seriously doubt it. | ||
| Dom Vitarella (Dom)
Junior Member Username: Dom Post Number: 106 Registered: 11-2002 |
Hmmm, so I gather the black mystery wire coming out of the firewall by the drivers side tank is not the tach wire. Maybe if I remove the wheel and look for it in that area. I wish I was there when he installed the ignition so that I could see how the original set up was set up. Dom | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 966 Registered: 4-2002 |
Dom: My GT4 has a large soft plastic conduit running up the firewall near the left gas tank. Some wires exit at this point for the tank itself, and then the conduit continues somewhat hidden on an upper frame rail, where wires for the ignition system exit. The tach wire exits the wire loom there. Near the gas filler neck. The wire is black on my car. What is puzzling is that I also have a black "Mystery Wire" not connected to anything exiting the loom near the gas tank. ??????? | ||
| Ben Millermon (Brainsboy)
Junior Member Username: Brainsboy Post Number: 143 Registered: 5-2001 |
Yeah the MSD tach adapter should work for you. You may need to add a 2.2K resistor between it and the tach if the tach go's crazy over 5000rpm. Anyhow, for my Millermon Conversion distributors (and going from 2 to 1 distributors) I had to design a special tach adapter. By the way I have a MSD8910 tach adapter your welcome to have it, if you havent already bought one, im not going to need it. I would rather have someone use it then let it sit on my shelf for 20 years. | ||
| Dom Vitarella (Dom)
Junior Member Username: Dom Post Number: 105 Registered: 11-2002 |
But where is it entering the engine compartment? I've searched and searched, and this black wire is the only one I see not attached to anything. I can't find a brown wire for the life of me. Dom | ||
| Mitchell Le (Yelcab1)
Member Username: Yelcab1 Post Number: 503 Registered: 11-2001 |
It was originally attached to the 1-4 dizzy, probably running down and hanging loose near the coils. | ||
| Dom Vitarella (Dom)
Junior Member Username: Dom Post Number: 104 Registered: 11-2002 |
Hi Ben, I purchased the MSD 8910 tach adapter. The installation of the MSD was done at Veloce Speedesign in San Jose (I am currently in Orange County). It retains the original dual distributors, but has the pertronix triggering. So, I have 2 MSD 6A's, along with 2 Blaster Coils. The MSD's are hooked up with the white and red wire going to the distributor, and the orange and black going to the Blaster Coil. According to MSD, I need the 8910 tach adapter. But, I'm not sure where the tach wire is. According to MSD, the tach wire should be spliced into the white MSD wire (not at the neg coil where it was originally). Unfortunately, the tach wire is not hooked up to any of these locations, and I am trying to figure out if the tach wire is the wire I think it is. I'd hate to connect the wire and have it blow something because it is the wrong wire... Dom | ||
| Dom Vitarella (Dom)
Junior Member Username: Dom Post Number: 101 Registered: 11-2002 |
Hi Ben, I purchased the MSD 8910 tach adapter. The installation of the MSD was done at Veloce Speedesign in San Jose (I am currently in Orange County). It retains the original dual distributors, but has the pertronix triggering. So, I have 2 MSD 6A's, along with 2 Blaster Coils. The MSD's are hooked up with the white and red wire going to the distributor, and the orange and black going to the Blaster Coil. According to MSD, I need the 8910 tach adapter. But, I'm not sure where the tach wire is. According to MSD, the tach wire should be spliced into the white MSD wire (not at the neg coil where it was originally). Unfortunately, the tach wire is not hooked up to any of these locations, and I am trying to figure out if the tach wire is the wire I think it is. I'd hate to connect the wire and have it blow something because it is the wrong wire... Dom | ||
| Ben Millermon (Brainsboy)
Junior Member Username: Brainsboy Post Number: 141 Registered: 5-2001 |
Im curious to which tach adapter you purchased. Also was your car original duel distributors and converted to a single? | ||
| Dom Vitarella (Dom)
Junior Member Username: Dom Post Number: 100 Registered: 11-2002 |
OK, hope this isn't a dumb question, but... Where is the damn tach wire located? I have an MSD ignition previously installed, and should be getting the tach adapter tomorrow. The tach was disconnected upon installation because the mechanic did not have the tach adapter. There is a black wire coming out of the firewall that is not connected to anything, and I would like to assume that this is the tach wire. I've searched the archives, and descriptions of the tach wire is a Brown wire. Well, I'll be damned if I can find a brown wire, only the black wire coming from the firewall on the driver side. Can I assume that the black wire is the tach wire? The length of the wire does reach to one of the coils. Is there some way to test without damaging the system? Thanks, Dom (eagerly awaiting a functioning tach) |