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Home >> Mercedes Benz >> 1984 >> 190E Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Fuel Injection System - BOSCH Cis-E >> Testing >> Choke System >> Choke System Check

Choke System Check

  1. Check switching-off point of additional air valve. With engine temperature below 70°F (20°C) engine should idle at approx. 900-1200 RPM. Idle RPM should drop to normal when operating temperature reaches approx. 160°F (70°C).
  2. If cold start idle is too low, compress connecting hose between idle speed air distributor and additional air valve. If no RPM change occurs, the additional air valve seizes and must be replaced.
  3. If idle RPM is too high at operating temperature, pinch connecting hose between idle speed air distributor and auxiliary air valve. If idle speed changes, the auxiliary air valve sticks or is electrically not heated. Nominal voltage should be approx. 12 volts.
  4. Pull off wire plug on cold start valve, disconnect volt/ohmmeter. Pull off plug of transmitter for ignition distributor on switching unit (Green cable) or Protective Plug (102 589 02 21 00) on diagnosis socket.
  5. Check starting voltage. Actuate starter for a moment and read off voltage. Reading should be at least 10 volts.
  6. Check air flow sensor plate and control piston for easy operation, fuel pressures and internal leaks. If normal fuel pressures are not achieved, check coolant temperature sensor. After starting, increase acceleration enrichment.
  7. Check cold start valve for function and leaks. Disconnect fuel line on cold start valve. Remove cold start valve and reconnect fuel line.
  8. Hold cold start valve into a container. Pull off cable on thermo-time switch. Place connection "W" on plug to ground. Start engine. Fuel coming from cold start valve should be in the shape of a cone. Below 45°F (5°C), it is not necessary to pull off cable on thermo-time switch.
  9. Dry cold start valve at nozzle. No formation of drops should occur. Remove contact bridge. Mount cold start valve with new gasket. Plug on again wire plug on cold start valve, mount relay and fuel line.
NOTE: During warm-up stage and at operating temperature, the controlling element is energized by a given current which is determined by coolant temperature sensor, oxygen sensor and ECU.
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