W198 300SL
from Carburetors to Fuel Injection:
BRINGING the World's First SUpercar UP TO SPEED
It's hard to believe the W198 300SL debuted almost 70 years ago but even with it's numerous innovations and safety features, there was plenty to improve upon throughout its development.
Originally introduced with carburetors as the W194 racecar, fuel injection was introduced for the 1953 season and was used in the production vehicle, released in 1955, as well. Though complex and expensive, fuel injection provides better fuel economy, fewer emissions, and generally better performance, all important aspects of a high-performance sports car.
Fuel Injection Pumps for the
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Flow Testing Quantities of The Bosch R3
The PES6KL70/320 R3 seen here is a 6-plunger model which provided improved efficiency and allowed adjustments to individual plungers and, in effect, injectors. Its inline design and layout also carried over to later fuel injection pump development as seen in the W113 pumps from the 60s and 70s such as the R11, R18, and R20 series.
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This pump is an example of a pneumatic governor pump. Check out the link at the bottom of the page for more info specific to pneumatic governor pumps. More on the PES6KL70/320 R2 and PES6KL70/320 R8 coming soon.
300SL Pumps
Bosch PES6KL70/320 R3
PRODUCED FROM 1955-1958
MODEL: W198 300SL "GULLWING"
The PES6KL70/320R3 is an example of a pneumatic governor pump and was produced for use in the famed W198 300SL Gullwings.
As fuel injection pumps continued to be improved upon they became the standard method of getting fuel to the engine over the decades with the inline setup becoming the go-to design for Mercedes-Benz vehicles moving forward.
Here you can see an R3 during the reassembly process, displaying the inner workings of the pneumatic governor and camshaft. Below that you can see some comparison pictures of a purportedly restored R3, but with wear and grime that indicates a lack of disassembly, calling into question the quality and effectiveness of the previous restoration.
It's not just a "looks" thing either. Old gaskets and seals will result in leaks and suboptimal performance. Even worse, grit and grime can loosen and get injected directly into the engine, potentially causing damage or catastrophic issues.
Simply put: If you're not getting a fully restored fuel injection pump you're wasting time, money and opening a door to future issues.
300SL Pumps
Bosch PES6KL70/320 R8
PRODUCED FROM 1958-1963
MODEL: W198 300SL "ROADSTER"
The PES6KL70/320R8 is an example of a pneumatic governor pump and was produced for use in the famed W198 300SL Gullwings from 1958-1963.
Though similar to the previously seen R3, some differences include plunger guide screws returning to the front of the pump housing (seen above the viewing port) and the removal of inlets and outlets on the upper right and left of the front of the body.
This pump recently went through a deep clean in the ultrasound bath, media blasting, and hand polishing. The interior parts are due for the same process after which the pump will be reassembled and move on to the testing and calibration process.
300SL Pumps
Bosch PES6KL70/320 R2
MODEL: W198 300SL "GULLWING"
The PES6KL70/320R2 is an early pneumatic governor fuel injection pump produced for use in the famed W198 300SL Gullwings.
The pump here can be seen in the state in which it was received before any restoration and minimal disassembly has been started by Black Forest. This pump had gone through a previous restoration, like many others, but questions remain regarding the quality of that restoration and its current operating status. You can see differences between the state of this pump and restored pumps such as the plating material, color and finish, incorrectly plated parts, and overall cleanliness of the interior and pump surface, among other things.
Bosch 300SL Fuel Injection Pumps
Vintage Documents
Getting the original supercar Running RIGHT
Believe it or not even aspects of the original supercar have fallen through the cracks. We see countless 300SL pumps that are in desperate need of work and often leave their cars running poorly, even if the owner isn't aware. Much like other models we used a combination of trial and error and vintage documents such as those seen here.
300SL Pumps
Fuel Feed Pump
THE BOSCH FP/KLA 22 K2 & FP/KLA 22 K1
Along with the fuel injection pump itself, the fuel feed pump is an essential but often overlooked part of Mercedes-Benz restorations. Despite appearances, this small attachment is deceptively complex and requires just as much expertise to rebuild and restore as the fuel injection pump itself. Furthermore, because so few fuel injection pumps are restored in the first place, fuel feed pumps are even less likely to have received attention and regularly are found in poor condition negatively effecting the performance of the vehicle even after so-called full restoration projects. Even many fuel injection pump restorers have ignored the internal mechanics of the fuel feed pumps for decades, leading to inaccurate testing and calibration which leads to incorrect adjustments to get the car running more smoothly.
We not only restore Bosch EP/KLA 22 K2 and FP/KLA 22 K1 fuel feed pumps using the same meticulous process as our fuel injection pumps, but we're also working on an exchange for fuel feed pumps that are beyond repair or the missing piece to complete your restoration.
Here you can see our fuel feed pump housing and some of the internal parts after going through the refinishing process. Each has been machined to exacting specifications for optimal performance and tested to ensure all refinished feed pumps operate appropriately.
If you take a look inside the fuel feed pump body you will see that we remachine the interior to remove any imperfections or wear to ensure ideal pressure and performance of the piston. We also refinish the surface, interior and threads of the piston itself so all parts are working at their optimal capacity.
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Whether you need an entire fuel injection pump and all the accessories or just the fuel feed pump, contact us today to see what we have available and get your project scheduled.
Fuel Feed Pump
Suction Valve
NO PART IS TOO SMALL TO RESTORE
The suction valve can be found within the fuel feed pump and allows fuel to flow through the opening pressure valve into the pipe leading to the fuel filter. Even microscopic pitting such as that seen in these photos will prevent the valve from creating a tight seal, causing leaks and effecting the resulting fuel flow.
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We fully disassemble all parts of the fuel injection system including the fuel feed pump so that every piece can be individually inspected and any issues found can be addressed and corrected. Repairs done without full disassembly are guaranteed to miss problems like this and will result in less-than-ideal performance despite any other work done.
BEFORE
AFTER
Fuel Injection Pumps
Throttle Housing Jet Kit
Getting YOUR ENGINE IN TUNE WITH A CALIBRATED FUEL INJECTION PUMP
While a good fuel injection pump restoration can go a long way, if your throttle housing jets aren't providing the correct vacuum signal, the fuel injection pump can only do so much. Even if you think your vehicle ran well before, installing a restored pump introduces new variables which won't align with the wear of unrestored parts, and, as a result, your vehicle will run differently. Replacing the jets is the only way to ensure our calibration carries over to your specific engine performance. We offer full sets of throttle housing jets in a high-quality Haliburton case so that you can
ensure your pump is getting everything it needs to operate effectively
after installation.
300SL Fuel Injection Pumps
Housing Comparison
UNDERSTANDING ThE EVOLUTION OF THE 300SL FUEL INJECTION PUMP HOUSING
Though similar at first glance, there are many differences between the R2, R3, and R8 fuel injection pumps produced for the W198 300SL that led to improved performance and better calibration. In the following images and paragraphs we will outline these changes, explain how they effect the operation of the pumps, and show the gradual evolution which eventually resulted in the W113 pumps including the R11 and beyond.
The PES6KL 70/320 R2 is a pneumatic governor pump built for the W198 300SL and features the inline setup that would be used for Mercedes-Benz vehicles moving forward. Main differences from later pumps are a smaller viewing port, roller tappet guide screws below the viewing port on the front side of the housing, location of the fuel feed pump, and locating pins above the viewing port.
PES6KL 70/320 R2
PES6KL 70/320 R3
The main differences between the PES6KL 70/320 R2 and R3 are the location of the fuel feed pump and roller tappet guide screws and an asymmetrical bottom screw orientation. The guide screws shifted to the rear-side of the pump allowing the movement of the fuel feed pump, noticeable due to the elongated shape left over and the asymmetrical bottom plate. This change allowed the fuel feed pump to use an existing camshaft lobe whereas the R2 feed pump required its own as it didn't line up appropriately with the existing lobes.
PES6KL 70/320 R8
The PES6KL 70/320 R8 is the last pump used in the W198 300SL and bears many hallmarks of later pumps such as the PES6KL 70/120 R11. Differences on the frontside include the elimination of the elongated shape around the fuel feed pump and removal of the fuel inlet and fuel bleeder. The locating pins have shifted to the rear, and there is also an additional screw hole at the bottom-rear which is for the oil feed line securing bracket.
Camshafts
PES6KL 70/320 R2
PES6KL 70/320 R3 & PES6KL 70/320 R8
Here you can see the camshaft from the R2 in comparison to that found in the R3 and R8. The R2 features an additional lobe for the fuel feed pump in between the fourth and fifth lobes. This is due to the placement of the fuel feed pump which did not line up with either fourth or fifth lobes. When the roller tappet guide screws were moved to the back on the R3 the fuel feed pump could shift right and use the fifth lobe rather than requiring its own. This simplified manufacturing saving time and money.
Bottom Plates
PES6KL 70/320 R2
PES6KL 70/320 R3
As a result of the shifting fuel feed pump location, one screw on the bottom plate had to be moved, resulting in the asymmetrical layout seen here. The elongated shape around the screw hole remains on the R3 but was removed on the R8. They also added additional bracing to the underside of the plate for increased strength.
The cavities seen in the bottom plates actually come from an earlier design; felt pads which lightly rubbed the camshaft lobes were seated in these circular spaces. These pads are not present in later pumps, though the spaces remain.
PES6KL 70/320 R8
Camshaft Bearing Covers
PES6KL 70/320 R2
PES6KL 70/320 R3 & PES6KL 70/320 R8
Another difference between pump models can be found in the camshaft bearing cover. The R2 and early R3s used an aluminum cover while later R3s and the R8 used steel. The steel models also featured two notches to help in removal. A flat screwdriver can be inserted into the gap and used to pry the plate off the housing for easier disassembly. Previously a special tool had to be used to push the plate out from the other side of the pump housing.
