Sun 1020

Sun Tester Limited (Norfolk). Tach combustion unit U-801-

Companies like the Sun Electric Corp., of Crystal Lake, developed equipment to test automobile components and analyze engine performance. Serviceable older models of the machines these companies made are found in the garages of many old-car restorers today. Engine analyzers and distributor testers are the most common types of equipment seen in the old-car hobby.

As the name implies electronic engine analyzers were designed to diagnose the condition of a car’s engine. Speedy analysis was an important feature when it came to selling the machines.

Since there were small repair shops and big ones, the analyzers came in all sizes. Sun offered individual testers for volts-ignition, tach-dwell, vacuum pressure, combustion efficiency, cylinder leakage, coil circuitry and condenser resistance. These could be used as hand-held instruments or mounted together in a headframe on top of a rolling steel cabinet. This approach allowed small shop owners to buy one tester at a time and slowly build their own testing console.

The 920 – an upgraded 1020 model – and the 1120 could be adjusted to work with 6- or 12-volt electrical systems and on four-, six- or eight-cylinder engines. These could also be set for positive- or negative-ground electrical systems. Five automobile engine functions could be completely analyzed: starting, ignition, carburetion, compression and charging.

To check the condition of the vehicle’s battery and starting system, the mechanic read the voltmeter to analyze cranking voltage. Scope readings were used to test the coil, ignition and primary circuit for cranking coil output. A vacuum gauge gave a read-out of the cranking vacuum to help the mechanic assess mechanical factors that might affect starting. The tester’s vacuum gauge could also be used to do a PCV test of the positive crankcase ventilation system.

The machine could make five tests while the vehicle was running at idle speed. The tachometer displayed the idle speed and allowed adjustments. A dwell meter allowed setting the breaker point dwell. An adjustable timing gun – called an “electronic strobe-flash Timing-Advance unit” – plugged into the console and allowed initial timing settings at idle speed. A fuel mixture test using the combustion efficiency tester showed condition of the carburetor idle circuit. The vacuum gauge tested manifold vacuum and indicated engine idle efficiency.

A Sun tester came in handy for taking various readings at a 1,000 rpm “cruising speed.” Nine tests could be done in this range. The dwell meter indicated dwell variations and the distributor’s mechanical condition. The combustion efficiency tester assessed fuel mixture settings and tested carburetor air bleeds and float levels.

The oscilloscope near the center of the console allowed six tests at cruising speed. The scope included a pattern selector dial that served as an on-off switch and also allowed mechanics to pick three different types of patterns to view: superimposed, raster and display. The superimposed pattern showed the patterns of all cylinders on top of one another and indicated the overall uniformity of the ignition system. The raster setting allowed a mechanic to identify a specific cylinder’s pattern while viewing all cylinders at the same time. The display setting showed firing lines for each cylinder and allowed the firing voltages of all cylinders to be measured individually or simultaneously.

The superimposed setting could be used to test coil polarity and cam lobe accuracy. In the raster mode, the scope revealed condition of the secondary circuit, condition of coil and condenser and breaker point condition including point close, bounce and arcing. When set to “display,” the scope readings reflected the fuel mixture setting and tested the mixture, compression and plug rotor gap.

Other settings on the machine allowed the mechanic to load the engine as if it was running at 2500 rpm. This was called the “Turnpike” mode and was used in six tests. The timing advance unit could be used to test advance and assess whether the distributor’s mechanical and vacuum advance mechanisms were functioning properly. The scope (display setting) could be used to test maximum coil output (condition of coil, condenser and primary) and secondary coil insulation (condition of high-tension wires, distributor cap and rotor).

To make different tests, the electronic engine analyzer came with various leads routed through a swiveling u-shaped arm that sprouted from the top of the console. These had clips or nipples on the ends to be attached to different electrical connections or grounding points. There were also vacuum hoses and accessories like a fuel pump tester. Such devices and connectors could be stored behind the doors in the cabinet. A complete instruction book showing how to make hook ups and how to read the oscilloscope was provided.

Assembly: King’s Lynn (United Kingdom)

Years of production: 1960s—1970s

Length: 1066 mm

Width: 686 mm

Height: 1727 mm

Watts: 60

Cycles: 50/60

Revolutions Per Minute: <10,000

ZiL Museum (Moscow, Russia)

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