The Dawn of Fuel Injection
2-PLunger Fuel Injection Pumps
Bosch fuel injection pumps provided increased performance, fuel efficiency, cleaner emissions and more control over the performance of the pump in relation to the engine, allowing minute adjustments to improve overall performance.
While designs advanced at a rapid pace throughout the decade, earlier pumps like the ZEA R3 (pictured) still marked a vast improvement from carburetors and were used by Mercedes-Benz on their luxury models as early as 1958. The R3 seen here was used in coupes and cabriolet variants of high-end models such as the W128 220SE "Pontons" from 1958-1960, and early W111 220SEbs. It was also used in the famed W198 300SL "Gullwing."
THE ZEA: R1, R2, R3, R4, R5, R6
The ZEA is the first iteration of the 2-plunger pump and was first released in 1958. Features include black oxide plating, a long control lever in comparison to following models, and an extended corrector assembly. While an improvement on carburetors, a 2-plunger pump, as the name indicates, has only two plungers meaning adjustments apply to half of the injectors. Because of this individual injector performance cannot be controlled as it can in later 6-plunger models. This still allows greater adjustability than a carburetors but left room for improvements.
ZEA MODEL DATES
EP/ZEA 2 KL 75 R1: Feb 1958-Feb 1959
EP/ZEA 2 KL 75 R2: March 1959-June 1959
EP/ZEA 2 KL 75 R3: July 1959-Dec 1959
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THE ZEB: R11, R13, R14, R16
The ZEB model was first released in June of 1962 with the R11 and the R13 and featured a number of improvements from the ZEAs. Various mechanical adjustments include modified pressure valves and increased idle performance. Obvious differences include the replacement of black oxide plating with more resilient zinc plating and the reduced size of the corrector assembly extending from the right-upper-portion of the pump on the R3 allowed easier access to the governor, better idle control and more room for install and removal of the pump. Below you see images from the testing of an R14 ZEB, an example of early ZEB pumps. This pump was only tested and calibrated and did not go through a full restoration at Black Forest.
In the cutouts we have a fully restored R16, a later example of ZEB pumps. Scroll down for more information and images on that model.
INFO TO COME
ZEB MODEL DATES
R16
The following images show a fully restored R16 which is a later ZEB model produced after 196X. The R16 was used in models such as W189 300d and WXXX XXXSEb along with very early examples of the WXXX XXXSEL.
This R16 was fully restored in the Black Forest pump shop which included media blasting, ultrasonic cleaning, replating, replacement of all wear items such as seals and gaskets, and was meticulously tested and calibrated using our restored 2-plunger dedicated Bosch EFEP 385A.
Check back next week for a video showing the testing process of this R16.
