Electro-Hydraulic Actuator Valve (000 070 3962)

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Electro-Hydraulic Actuator Valve
0000703962.JPG
Part number(s) 000 070 3962 (kit)
Used on M102
M103
M104
M116
M117
M119

Description

The EHA (Electro-Hydraulic-Actuator) is an electrical valve that controls the pressure on fuel distributor. The duty cycle of the EHA valve is determined by the O2 sensor. The EHA valve is only used on vehicles with the KE-JETRONIC fuel injection system.

A bit of background on the EHA's function: it is an electronically controlled servo (controlled from the CIS-E main computer) that uses a variable current to make the last, minute adjustments to the fuel flowing into the fuel distributor and then into the combustion chambers. It does this by maintaining an appropriate differential pressure between the upper and lower chambers of the CIS-E fuel distributor. Essentially, depending on the current, the EHA is sort of a controlled fuel leak that can either richen or lean out the mixture based on its fixed adjustment, and the current that provides its inputs. The EHA works in conjunction with the fuel-air mixture adjustment (duty cycle) as described earlier. The EHA is sort of a final compensation in the system to try to keep it within proper operating parameters. If something else in the fuel/air system is not set or working correctly (for example, the idle air control "silde" valve, or the air/fuel mixture is not set correctly) then the EHA will do its best to try to keep things in check. If they are too far out of whack, then the EHA can only do so much given its parameters. [1]

Removal / Installation

M102 / M103

  1. Remove air filter
  2. Locate EHA valve behind the fuel distributor
  3. Unplug 2 prong wire connector
  4. Remove the 2 screws holding the EHA valve to the fuel distributor with either a flat head or Torx bit, depending on the model year.
    1. Use caution when removing the EHA valve as there may be fuel spray from pressure release while unscrewing the part.
EHA valve located behind the fuel distributor on an M103
  1. Installation is reverse


Adjustments

EHA adjustment screw

Although the EHA valve receives it's duty cycle from the O2 sensor, adjustments to the fuel pressure can be made.

  1. Locate the flat head screw on the back side of the EHA valve
  2. Remove this screw cover, being careful not to strip it
  3. A 1.5mm or 2mm hex screw can be adjusted
    1. Clockwise makes the fuel mixture rich
    2. Counterclockwise makes the fuel mixture lean
    3. Only adjust in 1/8th turn increments and testing the new settings to avoid over-adjustments


Troubleshooting

There are 2 small o-rings that seal the EHA valve to the fuel distributor. As these wear out from old age, fuel pressure may leak from this area and cause issues such as difficulty starting, incorrect fuel mixtures, etc... These can be easily sourced online by searching 2430210041 online and replaced. More often than not, these o-rings go bad before the EHA itself goes bad.

Replacements can be ordered from Bosh. New part numbers can be looked up on Bosh's page on Pressure Regulators.