This is part four and the final installment on our 1946 Packard Standard 8 series "Solving the Mystery of Power Loss and Backfiring at Fast Idle." (See www.southernwheels.com Archives section for parts 1, 2 & 3.) It has been a comprehensive series going through the complete fuel and ignition systems. Our final conclusion was that the problems were caused by 1. Incorrect timing, 2. Frayed spark plug wires causing cross-firing and 3. A non-working vacuum advance.
This month I will show you some of the test equipment and how it is used. One of the first things we did was to run a compression test Our '46 has 10mm spark plugs, so getting a 10mm compression tester can be a problem and might involve a trip to NAPA or buying adapters online ($10). The adapters are handy because they can adapt a 14mm to a 10mm on compression testers, TDC whistlers, etc. To do the compression test, put the car in neutral, remove the coil cable to the distributor and chock the wheels. Remove the spark plug wires (mark them) and plugs. We used a remote starter switch ($10 online) and tested #1 cylinder by cranking the engine over 8-10 times. We made a log of each cylinder reading, then did it again. Cylinders on old cars should be around 100 psi. Ours were 90close enough. If any cylinder reads more than 10 psi below the average, there is a problem in that cylinder. After testing, we reconnected the spark plug wires and coil.
Another test that is one of the most basic and gives you most all of the engine's vital signs is the Vacuum Gauge test. Our car has a 1/4" pipe thread plug in the intake near the firewall. To hook up the gauge with the engine off, remove the plug and screw the rubber hose from the vacuum gauge in. Warm and at idle, the engine should produce 18-20 inches of vacuum. Tests should be made at start-up, idle, medium and fast idle. (See SW Archives, September 2008 for a chart of readings and conditions.)
Fuel Pressure Tester: We tested our pressure at the carburetor by temporarily removing the AC glass bowl filter. This left an open fuel line going to the carburetor. I put a plastic "T" with rubber fuel line connecting the In and Out of the T and the fuel gauge at the bottom of the T. I also clamped each connection. Even though the Packard runs at only 4-5 psi, the connections will leak. If an electric fuel pump is used, there should be four checks: 1. Ignition switch on but engine not cranked. This is "ignition pressure." 2. Start the car and check running pressure. This is "idle pressure." 3. High revsthis is "throttle pressure." 4. Turn engine off, let it sit for 10 minutes then check the pressure. This is "residual pressure." Your motors manual will give specific readings for your car. The fuel pressure and vacuum are the same gauge although we use a separate one for each test. (On a manual pump car, we only use steps 2 & 3.)
Digital Thermometer: I always check the battery in the thermometer first. A weak battery will give incorrect readings. The thermometer should be held 4-5 feet from the engine for the most correct reading. You just point and shoot (press button). Get several readings. I get one at the front, middle and back of the block. They all should be close, within 10% or so. If not, there might be a blockage in a water port or a blown gasket, block or head crack, etc. Also check the exhaust manifold and radiator.
Multimeter: All multimeters are not equal. There are analog and digital meters. While digital is easier to use and works on most model cars with alternators, the analog works better on generator testing. I did a voltage test at the battery on this car by touching the battery posts with corresponding leads on the analog meter, then revved the engine (warm) and the meter needle moved beyond the 6.3 volts of the charged battery. I also did this with a digital meter, and when the engine was revved, the display showed high random numbersway over the 7.4 that is correct for a 6-volt generator's maximum output.
Coil Tester: (Universal Model 705 by Orbit Laboratories, Inc.) With the coil on the car and the engine off, disconnect the coil. Step 1, connect the 2 white leads to your car's battery, one to the (+) and one to the(-) posts. Step 2, connect the 2 black leads. One to your coil's positive and one to the coil's negative terminal. Step 3, connect tester's single red wire to the central terminal of the coil. Test results: A. If the coil is good the light will blink B. Light will stay on if the coil is no good C. The bulb will not light if the coil is shorted
Timing Light: To check ignition timing, disconnect the vacuum line at the distributor going into the vacuum advance, and cap the advance end to prevent a vacuum leak. On the '46 Packard Standard 8, the vacuum advance can kick in at approximately 500 RPM's. This will cause an incorrect timing reading with the light. Timing idle should be less than 500 RPM's on this car. Connect the red clip on the timing light to the positive battery terminal and the black clip to the negative battery terminal. (On Positive or Negative ground cars, + to + and - to -) The leftover large clip goes on #1 spark plug, first removing #1 spark plug wire, then pushing on the timing light clamp and push the plug wire into top of clamp. This is to time off of #1 plug. With the engine off, mark with chalk or white paint the degrees on the harmonic balancer that you want to time on, and a small mark at the end of the pointer that points to the timing marks. Start the engine, aim the timing light at the pointer, and if it's on time, the strobing light will make the degree mark and the pointer tip to appear to align up. Example: If you want 6 degrees BTDC, the light will flash on 6 degrees BTDC appearing to make the pointer and degree mark stand still. If it doesn't, the distributor will have to be advanced or retarded as needed. (We always do this with a heavy rubber glove on.) Often when the distributor is locked down, the timing will change, so be patient. We used a 6-volt timing light, although we have a 12-volt, just to be in the period. It works fine, but the light is dim and the shop lights have to be turned off to see it. A 12-volt can be used on a 6-volt car by simply using a 12-volt battery (not connected to the car's electrical system. This is just for powering the timing light. We set it beside the car.)
Tach and Dwell Meter: The tach checks the RPM's and is connected to the car's coil. For positive ground vehicles such as our Packard, connect the black lead to the distributor terminal of the coil (+ side) and the red lead to ground. On negative ground cars, connect the other way around. Set the switch on the tester to "Tach." On a single-barrel carb, 1. adjust the idle speed screw on a fully-warmed up engine until the engine is at the manufacturer's specified "idle RPM. 2. Turn idle speed mixture screw in until the engine RPM's slow, then back it out until the engine reaches its highest RPM. This is the proper idle mixture for setting pre-electronic ignition vehicles. On 2 or 4 barrel carburetors, adjust each mixture individually.
For Dwell, switch slide to "Dwell." Dwell is defined as the period of time the ignition points remain closed during the ignition cycle. Excessive dwell results in point burning and rapid deterioration, while too little dwell reduces the spark voltage (should be 18,000-20,000 volts at plugs for pre-electronic ignition systems. This results in poor acceleration and engine misfiring at high RPM's.
With engine at idle, lift window on distributor cap (on cars so equipped ie: Delco window types) and turn adjuster until proper setting is obtained (see your motors manual). On single ignition point distributors with no window in cap, 1. Remove distributor cap and rotor, 2. Slightly loosen the ignition point's hold-down screw, 3. crank engine and turn points adjuster until proper dwell setting is obtained, 4. tighten hold-down screw and re-check dwell. The dwell for my Auto-Lite distributor is 27 degrees. If the dwell is greater, that indicates the points are too close. If the dwell angle is smaller, that indicates the point gap is too wide.
Smart Tach Plus: An easier way to check RPM's is with the Smart Tach. It's about the size of a cell phone and is battery operated. (Use rubber gloves when using it.) Press tach button repeatedly to select correct number of cylinders. Pause, then press tach again to choose 2 or 4 cycles. After setting cycles, wait for 0000 display; hold antenna about 1-2 feet above ignition wires (don't touch antenna) with engine running. RPM's will appear on the screen. For spark analyzer function press IP (ignition peak) button, hook antenna on a spark plug wire 3-4" from plug. Reading will appear on the screen in kilo volts (kv). 1 kv = 1000 volts, so multiply screen readings by 1000. Example: 20 x 1000 = 20,000 volts at plug. This is correct for old points/condenser systems. This Smart Tach Plus has been replaced by the Sheffield TA 500 Multisystem Engine Analyzer. They are around $235 online.
Generator Testing: This is becoming a lost art. keeping it simple, it's important not to fry your system! Knowing what kind of generator you have is where you start. The two basic systems are Internally Grounded "B" systemsFord, etc., and Externally Grounded "A" systems, as used on GM's, Packards and others. Your motors manual will show your system. On our B system, it is polarized by loosening the fan belt to allow the generator to motor, and momentarily touching with a jumper wire the voltage regulator's Batt and Gen terminals (don't touch the Field!). One caution is to look at the voltage regulator for the terminal placement. An OEM Auto-Lite voltage regulator might have the Batt on the left, Field in the middle and Arm/Gen on the right. An aftermarket one might switch them around. I had a friend once that said he always polarized by touching the outer poles. You can't do that! You have to know what you're touching. Voltage regulators can be the 2-or 3-coil type. The 2 coils are older, usually 1930's, and have a cutout coil and a voltage regulator coil. The 1940's-up are usually the 3-coil type. They are comprised of a cutout, amperage and voltage output regulator.
Voltage Regulator Unit: The regulator consists of three units; the circuit breaker (cutout relay), a current regulator, and a voltage regulator. Each unit must be tested individually.
Circuit Breaker (Cutout Relay or "BATT terminal): This is a magnetic switch permitting the generator to charge the battery and preventing the battery from discharging through the generator. It contains a set of contactsone stationary, one mounted on the armature, and two windingsthe voltage winding and the current winding. Its contacts are open when the generator is not operating. (It cuts the generator in and out.)
Current Regulator (or "GEN / ARM" terminal (Regulates AMPS): This is a magnetic switch employed to protect the generator from overloading by limiting the generator output to a safe level. The current regulator is mounted on the same base as the circuit breaker and voltage regulator, and all three units are enclosed by the same cover. The Auto-Lite current regulator unit has two windingsthe series winding and the reverse winding. It contains a set of contactsone stationary and one mounted on the armature, which are normally closed when the current regulator is not operating. The Delco-Remy current regulator unit has one winding of heavy wire, known as the series winding, which carries the full output of the generator. It contains a set of contactsone stationary and one mounted on the armature, which are normally closed when the current regulator is not operating. The Delco-Remy current regulator unit has a bi-metal hinge on the armature for thermostatic temperature control. This permits a somewhat higher generator output when the unit is cold and causes the output to drop off as the temperature increases.
Voltage Regulator (or "FIELD" terminal): This is a magnetic switch used to keep the voltage in the electrical system at a safe level. The Auto-Lite voltage regulator unit has one winding known as the "voltage winding." It contains a set of contactsone stationary and one mounted on the armature, which are normally closed when the voltage regulator is not operating. The contacts are in series with the field circuit and the current regulator contacts.
The Delco-Remy voltage regulator unit has two windingsthe current winding and the voltage winding. It contains a set of contactsone stationary and one mounted on the armature, which are normally closed when the voltage regulator is not operating. The current winding is connected in series with the voltage regulator contacts and the current regulator contacts in the field circuit. The voltage winding carries full battery voltage at all times when the cutout relay contacts are closed.
The Auto-Lite voltage regulator is compensated for temperature variations through the use of a nickel-iron magnetic bypass whereby a higher voltage is required to vibrate the contacts under cold operating conditions than is required under hot operating conditions.
Delco-Remy voltage regulators are compensated for temperature by means of a bi-metal thermostatic hinge on the armature. The bi-metal hinge will automatically regulate to a higher voltage when cold, and a lower voltage when hot. This is necessary, as it requires a higher voltage to charge a battery that is cold.
Either the voltage regulator or the current regulator of the three-unit regulator can operate at any one time, but never operate at the same time. When the battery is low or the current requirements of the electrical system are great, the current regulator operates to protect the generator against excessive output due to overload. When the load on the electrical system is great, the voltage drops; thus, the voltage regulator does not operate. When the battery is fully charged, the voltage regulator operates to maintain a safe voltage level. The generator output drops, thus the current regulator does not operate.
Regulator Checks and Adjustments: Inasmuch as the three units of the regulator are mounted on the same base under the same cover, it is advisable to test each unit in any check of the regulator. To check the closing voltage of the circuit breaker connect a voltmeter (0 to 15-volt scale, 1/10 volt graduations) from the "A" terminal of the regulator to ground. Slowly increase the generator speed and note the reading on the voltmeter the instant the contacts close. The closing voltage should be 6.5 to 7.0 volts. To adjust the circuit breaker closing voltage on Auto-Lite regulators, bend the lower spring hanger (the one nearest the base of the regulator) toward the regulator base to increase the closing voltage; bend up to decrease the setting. On Delco-Remy regulators, adjust the cutout relay closing voltage by turning the adjusting screw clockwise to increase the setting and counterclockwise to decrease the setting. Recheck the setting by slowing the generator until the contacts open and slowly increase the generator speed. Note the voltage at which the contacts close. Repeat the procedure if necessary.
Current Regulator: Next check the current regulator setting. Disconnect the lead at "B" terminal and connect an ammeter (0-50 amp scale) into the charging circuit at the regulator B terminal. During this test, the voltage regulator must not operate if an accurate setting is to be made. With the regulator at operating temperature, turn on the lights and accessories to prevent the battery from overcharging. Operate the generator at medium speeds and observe the reading of the ammeter. The maximum current regulator setting is 39 to 41 amps. To adjust the current regulator setting on Auto-Lite regulators, bend the lower spring hanger toward the base to increase the setting. Bend up to decrease the setting. On Delco-Remy regulators, turn the adjusting screw clockwise to increase the setting, and counterclockwise to decrease the setting.
After each change of setting, to check the adjustment: 1. Replace the regulator cover, 2. Cycle the generator by reducing the speed until the circuit breaker contacts open and then bring the generator speed up as required, 3. Make sure the regulator is at operating temperature, 4. When completed, remove the jumper wire from the voltage regulator.
Voltage Regulator Setting: There are two methods for accurately checking the voltage regulator. The fixed resistance and the variable resistance method. Fixed Resistance Method: Disconnect the lead at the regulator B terminal. Connect a ¾ ohm resistance and a (0 to 10 volt scale) voltmeter from the B terminal to the regulator base. Operate the generator at medium speed and observe the voltmeter reading. Voltage regulator should be set at 7.2 to 7.4 volts. In making the voltage regulator check, the regulator must be at operating temperature, the regulator cover must be in place and the generator must be operating at medium speed, when the voltage reading is taken. Variable Resistance Method: To check the voltage regulator setting by the variable resistance method, a ¼ to 1 ohm variable resistance, and ammeter and a voltmeter are used. Any good combination testing instrument which includes these units may be used. Disconnect the lead at the B terminal of the regulator. Connect the ammeter and variable resistance in series into the charging circuit at the B terminal of the regulator. Connect the voltmeter from the A terminal to the regulator base. Operate the generator at medium speed. If less than 8 amps are produced, adjust the variable resistance unit until the generator output is adjusted to 8-10 amps, and then after cycling the generator, observe the operating voltage. Be sure the regulator cover is in place, that the regulator is at operating temperature and that 8-10 amps are flowing in the line. Adjust the voltage regulator to 7.2-7.4 volts on Auto-Lite regulators by bending the lower spring hanger toward the base to increase the setting. Bend the hanger up to reduce the setting. On Delco-Remy regulators, turn the adjusting screw clockwise to increase the voltage and counterclockwise to decrease the setting. After each change of setting, to recheck the adjustment: 1. Replace the regulator cover, 2. Cycle the generator by reducing the speed until the circuit breaker contacts open and then bring the generator to medium speed, 3. Make sure the regulator is at operating temperature, 4. Readjust the variable resistance to return the current to 8-10 amps. Remove the test instruments and connect the lead at B terminal. Note: Adjustment should be confined to bending the lower spring hanger only. If the regulator is faulty or badly out of adjustment, so that an accurate adjustment cannot be obtained, the regulator should be replaced with the same type and model unit.
These tests are relatively simple, and can keep your car running as it should, and will save you a lot of money by not just throwing parts at the problem! Keep 'em running, and keep 'em driving!