1.Bad GroundsIt's standard: You overkill the positive side of the 12-volt circuit and ignore the ground circuit. Basic electrical circuit design requires a complete path back to the battery through the ground circuit, and if it has high resistance, then the electrical device will operate poorly.
Bad grounds happen everywhere, but the worst case is when guys relocate the battery to the trunk, run a nice, thick multi-strand cable from the battery to the starter solenoid, then merely bolt the ground cable to the trunk floor or other easily accessible spot and leave it at that. A voltage-drop test (see page 58) on that ground circuit will probably reveal an inexcusable 1.5- or even 2-volt drop across the ground side of the circuit. The starter may crank when it's cold, but not once everything warms up (remember, resistance increases with temperature). The fix is to either run a large ground cable all the way up to the engine, or a large ground from the battery to the frame and another from the frame to the engine.
Another common grounding failure is an electric fuel pump pulling 4 to 5 amps. We often see pumps wired with a small, 14-gauge positive cable and further crippled with a corroded piece of piano wire for a ground. Improve the ground circuit with a larger 12-gauge wire and ensure that the ground circuit offers no more than 0.1-volt drop and the fuel pump will run much more efficiently.
The most dangerous bad ground comes from weak or small-wire grounds between the engine and the chassis and between the chassis and the body. These create resistance that can quickly overheat and in extreme cases begin to melt and catch fire. It sounds implausible, but keep in mind that the ground circuit must complete the current flow, so the ground side must always be as bulletproof as the positive side of the circuit.
2. Makin' The HookupEvery auto parts store in the country offers those cheesy crimp connectors with the little plastic sleeves that are supposed to provide a great connection. The problem is that these temporary fixes soon become permanent. Certainly one of the least effective electrical connectors has to be that one that pinches two parallel wires, hoping to make a connection. If you find one of these connectors in your car, cut it out immediately. And when you get them in the box with a new electrical goodie-especially a nitrous system-chuck them as far as you can.
There is some controversy over the proper way to make an electrical connection. Fans of solder will tell you that it prevents corrosion, but its detractors say it's too brittle and will eventually fail immediately adjacent to the connection. The problem with crimp connections-even when protected with shrink wrap-is that they are sources for corrosion. Either way, the following steps outline the right way to perform an electrical connection.
3. Alternator Charges Less Than Your GirlfriendOften the alternator is blamed for poor charging when the problem is actually bad wiring or connections. So try this quickie test. With the engine running, check the voltage at the output terminal of the alternator; on Terry McGean's Camaro, we found a high 15.7 volts. Next, measure voltage at the battery; McGean's was barely 13.5 volts, a loss of 2.2 volts in a circuit that should lose no more than 0.4 to 0.5. The Camaro suffered from multiple broken strands in the charging wire and several corroded connections. We added a large-diameter charging wire from a Painless Wiring high-amp alternator kit and improved the connection between the battery and the junction block using a MAD terminal block. Voltage drop across the circuit improved to 0.5 volt. Furthermore, by reducing resistance in the charging circuit, the alternator output voltage dropped back to a more reasonable 14.7 volts while voltage at the battery measured 14.2 volts.