The story of modern electronic fuel injection begins here: with the 1957 Bendix Electrojector.
The electionic fuel injection system found on virtually all gasolline production cars today has a father: Robert W. Sutton. An engineer at the Eclipse Aviation division of Bendix, maker of aircraft carburetors, Bob Sutton was quick to note he had plenty of help from his fellow engineers at Eclipse and other Bendix divisions. Experiments began in 1953 and vehicles with prototype EFI systems were on the road in 1955. For more info on the system’s engineering and development path there’s an essential SAE paper (570060) by Sutton and A.H. Winkler.
Unlike currrent EFI systems, the Bendix Electrojector’s circuitry was analog rather than digital. Microprocessors and IC chips didn’t exist. And since power transistors were so expensive at the time, the earliest control units (The Bendix term was “modulator”) used vacuum tubes, which Sutton noted took 30 seconds or more to warm up, so transistors were adopted as soon as it became practical.
Still, the Bendix Electrojector’s basic layout would be recognizable to any mechanic today. There was a high-pressure electric pump submerged in the fuel tank, a common-rail fuel distribution circuit, a central control unit, a throttle body, and a solenoid-operated fuel injector for each cylinder. But needless to say, no injectors or other components were available off the shelf—Sutton and crew had to invent them, generating a multitude of patent claims.
By contemporary standards, the components were primitive. For example, instead of a magnetic reluctor or Hall Effect switch to time and trigger the injectors, there was a second set of conventional breaker points built into the ignition distributor. The MAP (manifold absolute pressure) sensor was a spring-loaded diaphragm working a potentiometer, wired in series with another pot to report throttle position, creating a resistance sensor string for the modulator unit.
These analog signals (and a few others) were then translated by the modulator into a DC square wave with a variable pulse width, which was then sent through an amplifier to the individual fuel injectors. Each one was pointed at the backside of the intake valve for each cylinder, delivering the appropriate quantity of gasoline according to speed and load.
By 1955-6, Bendix was advertising the Electrojector in trade journals and promoting it in the workbench magazines. (Note that the display unit above is mounted on a Buick V8 mockup.) “Say goodbye to carburetor trouble,” declared the editors of Popular Electronics.. Invariably, the trade publications and magazines described the Electrojector’s modulator aka control unit as a “brain box.”
The first automaker to take a swing at the Electrojector was American Motors, which planned to use it on the 1957 Rambler Rebel.with its 327 cubic-inch V8. Rebel brochures prominently featured the fuel injection system, and an engine was proudly displayed alongside a Rebel at the 1957 New York Auto Show (above).
However, no Rebels with the unit were delivered to customers. Reportedly, the main problem that prevented the release was cold-weather starting. (The Electrojector used a conventional thermostatic coil and fast-idle cam for cold operation.) The Rebel got a Carter WCFB four-barrel carburetor instead.
Next came Chrysler, which thoroughly tested the Electrojector before advertising it and installing it on a few 1958 models. (Mopar experts say a total of 35 were produced: 16 Chrysler 300Ds, 12 DeSotos, five Dodges, and two Plymouths, though figures vary. Chrysler called its version “Jetpower” and the control unit an “integrator.”) While AMC used a single throttle body, Chrysler used two, a primary and a secondary, but the systems are otherwise similar.
Unfortunately, at Chrysler all the cars were soon recalled due to driveability troubles and retrofitted with standard carburetors. It seems the electrical components couldn’t handle the electrical interference and environmental conditions of real-world use. A handul of the units still exist, one or two in operating condition.
Bendix shelved the Electrojector program in 1960. As one executive noted, EFI didn’t add more perceived value to consumers than a $10 carburetor, but it cost 20 times as much. That would change soon enough. Bendix and Bosch of Germany formed a development and licensing agreement, which became critical in the ’60s as stricter emissions standards demanded greater precision in fuel/air management than carburetors could deliver.
The Bosch Jetronic electronic fuel injection (later renamed D-Jetronic) introduced by Volkswagen in 1968.was essentially a refined version of the original Bendix Electrojector. Through steady improvements, including feedback fuel control and digital processing, the industry eventually arrived at the advanced engine control systems we know today. Bendix also produced EFI systems, most notably for Cadillac, but never joined the major suppliers. In Motor City lore, it’s said that Bendix (now owned by Honeywell) earned far more revenue on licensing than on manufacturing its own EFI units.
Excellent article !! I knew Chrysler tried using EFI in ‘58, but was not aware of others wanting to use it, or the real history of it.
Bendix supplied the can-type MAP and baro sensors for the early GM computerized carburetor cars. The failure rate was close to 100 percent at the dealerships where I worked. It probably didn’t bode well for Bendix in the automotive electronics market.
A long-time friend named Chic, collected Chrysler 300 letter-series cars and Imperials. Chic worked at my restoration shop in the early 1980s, and one of the dozens of Chrysler 300s he owned was a ’58 Chrysler 300D with the Bendix fuel injection [sitting in boxes in the trunk], and the normal dual carbs mounted on the engine to make the car drivable. Chic said he was never able to get the EFI to operate at RPM’s faster than idle speed.
I remember one day we were looking at the EFI boxes in the trunk and I noticed what appeared to be a typical 392 ignition distributor, with a second, slightly smaller distributor jutting out sideways. Chic said that was the trigger unit to track when the fuel was supposed to be injected, and he could rarely get it to work.
I suspect Chic’s 300D is the one Jay Leno’s chief mechanic owns today
Of the two 1958 Plymouths fitted with the Bendix fuel injection unit, one was supposedly wrecked early in the game while the second car was owned by a man named Cass Lamb. I corresponded with him in his later years and he had driven his car, still equipped with the unit, almost 100,000 miles, claiming to have solved the problems of the original unit. The car supposedly spent some time in Mexico under his ownership but he later sold the car which has since fallen off the face of the earth. I have all of Cass’s manuals for the fuel injection unit.
Forgot to mention, I have one b&w photo of the car, a two door hardtop that appears to be white in color.
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I worked on most of the European cars, especially German, equipped with the Bosch D Jetronic as well as the later digital K. 90% of the D’s problems were resistance issues at the plugs for sensors. Next was the trigger contacts in the bottom of the distributor. We bought a system that plugged inline with the processor that “ran” the system with the engine off. In the end it taught us to do without it.