Easy Electrical Question

Mine goes from a bolt on the clutch spring support/cam cap over to a bolt on the frame near the throttle rod support. Omgjon has his in a different place in the pictures. Either will work. Mine is easy to get to. Made of very heavy copper braid that is about an inch longer than the straight line distance. About 3/4" wide and very flexible. Engine does rock some.
John

 

Steve - probably won't (solve your charging problem). Definitely install the ground strap, but the strap is primarily used to prevent frying of your throttle linkage, or choke cable, or other conduit providing high resistance ground back to the starter. When starting the car, the starter will pull 30+ amps, the positive cable is that 4 gauge wire running directly from the battery. Hence, you need a similar ground heading back to the battery. The engine mounts are insulated via the rubber or the paint of the chassis. The shift linkage will work, as will the choke, throttle, and clutch cable. None of these are great, large amperage conductors.

Let us know what happens when you add the ground strap, and then we can proceed with suggestions after that.

Jim S.

 

You also might want to connect the battery negative cable of the MSD box to the same ground connection as the grounding strap. The original ground wire going to the Dinoplex ground and coil is not a good reference ground, mine had a resistance of eight ohms against the chassis. As Jim said make sure that the battery negative also has a good ground reference, you should see less 0.1 ohm or less between battery negative and the engine.

 

Adrian - your intention is well founded and good, however, physically it is difficult to extend the wire from the MSD in the trunk to the ground-strap stud holding the oil-rebreather cannister on the firewall. This is a long traverse across the engine bay. While easily done, it requires extending the MSD wire, which by itself may add resistance to ground. The ground wire supplying the ignition system (Dinoplex) I believe runs above the right rear wheel-well to a stud on the right aspect of the engine bay. All grounds on the Dino terminate on the chassis via studs. An alternative to your ideal solution is to trace the ignition ground wire to its stud, remove the nut and wire, clean the chassis contact area at the stud with a wire brush attached to a portable drill, and spray with brake clean to clear residue. One should also apply sandpaper to the ring connector of the ground wire. Once these suggestions are accomplished the ground will be sound, that is, low resistance.

Your other suggestion, of refurbishing the ground connection at the battery, is right on, and quite important. I suggest that if this has not been done that all owners take the time to remove the ground wire from the battery to the chassis, and clean both ends. This includes wire brushing the chassis where it attaches to the chassis stud and sandpapering the ring connector.

Jim S.

 

I have installed the CD unit in place of the old Dinoplex unit and extended the ground/power cable using 2,5mm^2 wires soldered to the original CD unit cabling, measured resistance up to the soldering point was way below 0.1 ohm. Put the supply cables together in a protecting tube and routed the tube along the right side of the fender to the upper frame where the original tacho and ignition cables are installed. (See attached image, fat ground wire at bottom of ignition setup).
Didnt touch the original ignition ground wire for easy retrofit to the original Dinoplex setup. Another reason to leave it untouched was the somewhat small diameter of the original cabling.
You're right, it would be a more thorough approach to find the original problem and fix it, but i didnt really trust the existing cabling i guess
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Adrian - is that a Crane XRV700 optical pickup amplifier feeding the MSD? I found the wires to the distributor barely long enough to make it without splicing longer wires.

Jim S.

 

Steve - not at all counterproductive, but perhaps unnecessary. MSD calls for a positive and negative large gauge wire connected directly to the battery. A second red wire is connected to a switched positive. This is because the MSD draws approximately 1 amp per 1,000 RPM, hence, at 7,000 RPM the MSD box is pulling 7 amps. This is a good load, although not a really big load. While the MSD is connected to the power source continuously, it is not active until the smaller red wire is connected to 12 volts through the switch.

The wire feeding the Dinoplex, I believe, is adequate for the purpose. It is a 12-gauge switched positive source. As far as the negative, the chassis is always an adequate, if not desirable, ground. It does, however, force the issue of making sure that your ground wire at the battery to the chassis is well maintained.

Another source for your positive voltage/current is the starter cable. This is difficult to get to, and requires a large ring connector and routing away from the manifold, but it is equivalent to the battery terminal. Finally, a 12-gauge wire from the battery or the positive bus at the relay board to the trunk and MSD is certainly an alternative. It does mean that you have to route the wire over the wheel well, through the engine bay, down the rocker panel and to the forward spare tire area or battery. Since you have this much of a run, I would fuse the wire at the battery or relay panel bus, thereby preventing catastrophe should there be chafing and subsequent short circuit. This would not deter me, but would drive me to be careful with the position of the wire and with the addition of the protective fuse.

Jim S.

 

Jim, its an E-coil from Mallory with heat sinks. I'm using a Pertronix MR-161 hall pickup with integrated op amp instead of the Crane Xr700 with the external amp module, no problem to lengthen the pickup wires way into the luggage compartment. The MSD is actually a digital Hyfire 6AL, uses less power (see thread Dino Ignition Alternatives).

Steve, sorry for hijacking your thread

 

My alternative approach was to connect the MSD units positive feed to the top connector of the alternator fuse box in the engine compartment, so its right at the source. From there the feed cable is the routed to the right top rail over the fender and then back to the luggage compartment. Use a protective plastic tube to route wires through the engine compartment, helps with the temperature and reduces the risk of chafing.

 

Steve, the MSD 6 series has an internal fuse according according to the installation manual (found on page 5, 'power leads'), so you wouldnt need to add one. Check your (new) regulator first: the MSD is spec'd to run up to 16 volts and can stand peaks up to 24 volts, a fuse wouldnt be of any help if the voltage is too high.

In the original circuit, the fuse inbetween the alternator and the battery has 60 amps. The smaller fuse has 8 amps and goes to the voltage regulator. For 60 amp fuses the easiest option is the readily available Maxi Blade type. If you still have the original fuse box, you might want to rebuild it to use a Mini ANL type fuse.

 

Steve - As Adrian suggested, there is an internal fuse within the MSD that protects the main wiring bus should there be a short within the MSD box. However, the fuse that I referred to in my previous post is not to protect the MSD, but to protect your car from catching fire should the 12-gauge wire supplying current to the MSD chafe against the chassis. If you are taking the current directly out of the alternator, with or without a 60 amp fuse, your wire will lead to a fire should it touch chassis. It would be wise to place a 20 amp fuse immediately at the takeoff of the MSD positive lead where it gets its power. That is, if you are connecting it to the alternator output wire, then this fuse should be located at the alternator (or wherever you connect to the bus). You can purchase a pig-tail slotted modern fuse holder at any shop. Crimp your connector on to one side of the pig-tail, and connect the other side to your MSD line.

In addition, as you have removed the battery ground wire and are cleaning all contacts, I might suggest that you do the same for the 8 gauge wire leading from the positive side of the battery to the relay board. On many old cars the positive bus wire is hanging by a few strands from the battery terminal. You might want to crimp a new connector on to this and clean all the contact points.

Hope this makes sense.

Jim S.

 

Which fuse blows, the one between the positive feed (large red cable) and the MSD box?
This happens as soon as you turn the starter? Any other symptomps?

1) Not sure that blown diodes would lead to this symptom, the fuse blows due to a too high current, a blow diode would lower the available voltage in most cases. This sounds more like a prolem with the voltage regulator or a grounding issue.
2) The condenser is for noise suppressing, its most probably not the fault here (come to think of it, i dont even have one on the E series). No harm removing it for testing.

- Please measure the voltage before and after the regulator, it should never exceed 14.2-14.6V after the regulator.
- Check the polarity of the voltage feed for the MSD (ideally the signal is checked with an oscilloscope to make sure no stray AC is coming from the alternator).
- You still might have a grounding problem, please measure the resistance against a reference point (battery minus to chassis) and several test points in the car (engine, different chassis grounding points etc). Resistance
should be below 1 ohm.