Mercedes-Benz R107 500 SL V8 Bosch K-Jetronic Diagnosis
Diagnosing Bosch K-Jetronic systems should always begin with accurate measurements rather than replacing parts by guesswork. In this article, we demonstrate the first steps of troubleshooting a Mercedes-Benz 500 SL (R107) equipped with the legendary M117 V8 engine, from verifying the mechanical timing to checking the complete fuel system
A Mercedes-Benz 500 SL (R107) equipped with the M117 V8 engine arrived at our workshop for a complete Bosch K-Jetronic inspection.
Many K-Jetronic problems cannot be solved by simply replacing components. In most cases, several small issues combine to create poor running, difficult starting or unstable idle. That is why every diagnosis at OTC Garage Hungary starts with systematic testing and precise measurements.
Step 1 – Checking the Engine's Mechanical Condition
Before making any adjustments to the fuel injection system, the mechanical condition of the engine must be verified.
During this inspection we checked:
camshaft timing
valve timing
ignition timing
basic engine condition
If the engine timing is incorrect, no K-Jetronic adjustment will produce satisfactory results.
Fuel System Inspection
The next step is measuring the fuel pressures throughout the Bosch K-Jetronic system.
Our inspection includes:
system pressure
residual pressure
fuel pump performance
pressure retention after engine shutdown
These measurements provide valuable information about the condition of the fuel distributor, fuel accumulator, pressure regulator and other components.
Electrical System Checks
Reliable diagnosis also requires a complete inspection of the ignition and electrical systems.
Among other things, we verify:
supply voltages
electrical switches
sensors
wiring integrity
ignition system operation
Electrical faults often produce symptoms that can easily be mistaken for fuel injection problems.
Diagnosis Continues
The diagnosis of this Mercedes-Benz 500 SL is still in progress.
In the next stage, every major Bosch K-Jetronic component will be tested individually. Once the fault has been identified and repaired, the system will be adjusted to factory specifications.
A follow-up article will present the complete repair process together with the final diagnosis and test results.