beermanpete

The wire used is ordinary copper wire coated with silicone insulation. Like any fuse, it needs to have a smaller cross-sectional area to ensure it melts before the circuit it protects, hence the 4 wire gauges smaller rule of thumb. The silicone insulation is used so it does not burn and cause a fire. As a result, the fusible link can open (do its job) without damaging the insulation which is why they are sometimes overlooked when troubleshooting a no-power condition.

Great! The diode needs be installed a particular way. Try turning it around. As for the type of diode, any 50 Volt (or higher) diode rated for 6 amps or more should work. Also, diodes don't like high temperatures so be carefull when soldering it to the wires. Use a heatsink on the leads (by lightly squeezing the diode lead with needle nose pliers between the solder joint and the diode) to keep the heat out of the diode. Too much heat will short out the diode.

Did you replace the differential mount? If that fails you will get a clunk when pulling away from a stop.

Test the fuel pump for output. If that is good then look at the floats and float valves and the fuel filter built into the top of the float bowl cover. Also, check the hoses at the botton the carbs to make sure they are not pinched or blocked.

My suggestions were for the orignal alternator with the external regulator. They do not apply to the internal regulator type. The behavoir you describe is typical for a properly functioning internally regulated alternator. When you start the engine and the alternator begins to charge the light will go out.

It sounds like you are making progress, which is good to hear. The charging system draws about 2.5 amps maximum. The 1156 bulb is about a 2 amp load normally, so the bulb will light trying to power the charging system, but not at full brightness. To test the regulator and alternator separately, start by leaving the regulator connected but disconnect the 2-wire connector from the alternator. The 1156 should stay dark if the regulator is good. Next, with the 2-wire connector removed and the engine off, use the ohmmeter and measure the resistance from the F terminal (on the alternator) to ground. The resistance should be about 5 ohms for the 40 amp alternator and 4.5 ohms for the 60 amp alternator.

Yes, it is normal to have a resistance reading from the positive terminal to the negative terminal (ground.) It is through this resistance that current flows and the device works. What we are looking for when testing with an ohmmeter is the correct amout of resistance, whatever that may happen to be.

Ok, thanks. These readings look fine. There is no short and none of these readings indicate a condition that would blow a 20 amp fuse. You have said that when you install the gauges the fuse blows and when you remove them the fuse does not blow. The only thing I can think of to cause this is when the ammeter/fuel gauge is removed there is no power to the entire car and therefor no current can flow to blow the fuse regardless of where the short is. To test this try connecting only the ammeter (the large white wire and the large white/red wire) leaving all the other wires for the fuel gauge and other gauges disconnected and see if the fuse still blows.

That's magic smoke, just to be clear.

When you took these measurements how did you connect the ohmmeter? Was one lead on the greem wire at the fuse block for all of these reading and the other lead on each wire in your list?

I don't know the Mastech either. I looked it up on the internet and found the owner's manual. This meter does not have a zero knob for the ohms.

Ok. So now you need to install the gauges one at a time to see which one causes the problem. The Mastech meter you are using is not autoranging. This means you need to select the correct resistance range for what you are measuring. When you get the "1" reading on the 2k range it does not mean you have an open circuit, it means the resistance is larger than 2000 ohms. Try selecting the higher ranges to see if you get a reading. Also, when the reading is .057 or some other low number (below .200) you can select the 200 range and get better resolution.

All of the suggestions above are good. To help determine which it is try using a remote starter to start the car. If it will start reliably with the remote starter, especially right after failing to start using the ignition switch, it points to high resistance in the wiring going to the ignition switch and then to the starter solenoid. This particular problem is more likely in the '74 and up years with the ammeter shunt and multiple fusible links due to having many more connections that the pre-74 models.

Yes, the temp gauge has calibration trimmers. They are accessed through little holes in the back of the meter housing. However, it would be easier to characterize the meter the way it is and get to know it. Once you know what "normal" is you should be fine.

We had a distributor in our 73 that would float the points at about 5000 RPM due to the wrong points cam (to sharp). The problem was very stable with respect to RPM and frequency of occurrence. Your description indicates some variability as to if and when it occurs. I suspect weak spark. Look at the DC voltage at the coil, resistance of the ballast and coil, condition of the plug wires, cap, rotor, and so on. A lean fuel/air mixture is harder to light and will show up weak spark, so it could be a combination of problems.

It sounds like you have voltage drop in the wiring to the ballast and coil. There should be a solid 12 volts before the ballast and about 9 volts after the ballast (on the coil).

You could use a regulator from a late 60s Ford if you don't mind rewiring the connector to fit.

The SU is better? Possibly. Proper set up and adjustment is very important and the SU has the home court advantage. I had a 260Z with DGVs and it ran fine and (using the butt dyno) made similar power compared to my 240Z with SUs with either a 240 or a 280 engine. From my measurements the DGV is has the same total area at the throttle valve bores as the SU so the total air flow is propably similar. The down draft configuration does require an elbow in the intake but on an otherwise stock engine I doubt it is the performance penalty that some people suggest it is.

Fuel dripping from the aux. venturi suggests high fuel level in the float bowl. The fuel level is normally very close to the level of the discharge port in the venturi. When the fuel level is a tiny bit higher than the discharge port it will drip out. Low the fuel level a little bit and see what happens.

In your first post you said, "I can actually see fuel coming out on this one." Where, exactly, is the fuel coming from?

Using the incorrect ballast resistor won't hurt the tach but it can damage the coil and points if the resistance is too low or it is removed. From what you have said it sounds like the tach is bad. Check the wiring at the back of the tach. It needs 12 volts and ground from the primary circuit in addition to the signal from the coil.

If the float is plastic it can absorb fuel slowly and get heavier but still float. This will change the realized fuel level, raising it and causing a rich conditon without having the classic sunk float fuel leak. Perhaps you could compare the two floats by weighing them or simply swap them in the carbs to see if the problem follows the float.

How did you "prove" the float level?

Sooty plugs means it is too rich. Look at the float. Perhaps the float is bad and has taken on fuel. This will cause the float to be less buoyant and sit low in the fuel, causing a high fuel level.

What do the plugs look like? From what you have said, I suspect the idle circuit is blocked or damaged. When you rebuilt the carb did you verify ALL passages are open and will flow fuel and/or air as required? What does the idle mixture screw look like? If the tip does not come to a point it could be broken off and stuck in the passage causing a blockage.