Understanding Your Fuel Injection Pump
DECODING THE INJECTION PUMP
If you know anything about German engineering, they like to keep things simple. Just kidding.
While the engineering and design of components for Mercedes-Benz vehicles already present a high level of complexity, getting information about those parts, especially when it comes to the classic era vehicles, can prove just as confusing and time-consuming. Not only are the manuals in German, but finding those manuals can be a virtually impossible task.
Something as simple as understanding a label can become a bit of a nightmare for anyone not already knee-deep in the history and legacy of these parts.
When it comes to fuel injection pumps, deciphering the naming code can help you not only identify the exact pump you have and if it is right for your vehicle, but can tell you quite a bit about the pump itself.
Simply put, each letter or number identifies a unique aspect of your pump, helping to identify and differentiate your pump from other generations. Unfortunately for the non-german speaking crowd, the letters don't exactly match up to the translation, but we can give you an idea of what each of those identifiers is telling you.
In the first grouping, the initial letters (PES in our example) define if the pump is inline (PE) or rotary along with the type of mount. The following number identifies the number of plungers, while the next grouping of letters identify the maximum plunger diameter of 7-7.5mm and if the pump is intended for use with gasoline.
The second grouping starts with the actual plunger diameter folllowed by the design change code. An "A" indicates a plunger and barrel element WITH oil blocking while a "B" signifies a pump WITHOUT. The final number in this grouping identifies the location of the fuel feed pump, with 120 indicating the pump does not have a fuel feed pump on the body.
The final grouping indicates the series number and an R or L for either a right or left direction of rotation. Some pumps also have an additional letter on the end, in this case a Y indicating the pump is for the US market.
Take a look at our individual fuel injection pump pages to learn more about your specific pump, or check out our pump map page to find out what's what on a Bosch fuel injection pump. (Pump pages and pump map coming soon!)