1986 Mercury Lynx Base, MTXIIFACTORY OEM SERVICE PROCEDURE

Fuel Injection System - 4-CYL Diesel: Testing: Injectors: Notes

WARNING: DO NOT  use diesel fuel. It is unstable with respect to corrosion inhibition and may cause skin problems. Pressure of atomized test spray has sufficient penetrating power to puncture flesh. When testing injectors, keep spray contained to avoid serious injury.
  1. Remove injectors from engine. Connect injector to Rotunda Test Stand (14-6300)
  2. Fill test stand using Calibration Fluid SAE No. 208629, No. J968D, or ISO 4113. Open stand valve and operate tester handle for several quick strokes to bleed air from injector.
    NOTE: It is advisable to test the injectors before cleaning them. Opening Pressure
  3. Open gauge valve and build up line pressure by slowly depressing handle until nozzle sprays fuel. Repeat operation until accurate and constant opening pressure is observed.
  4. Opening pressure should be 1957-2030 psi (138-143 kg/cm2 ). If opening pressure is not within specifications, correct by replacing adjustment shim. See Fig 1 .
    Fig 1: Exploded View of Injector Nozzle
    G3296
  5. Adjustment shims are available in sizes from .0197" (.50 mm) to .0606" (1.54 mm), in increments of .0016" (.04 mm). Each change in shim thickness alters opening pressure by approximately 68 psi (4.80 kg/cm2 ).
NOTE: During testing, injector nozzle chatter will vary for each injector. Lack of chatter does not indicate a defective injector. Tip Leakage

Wipe nozzle tip dry. Operate test pump to maintain pressure at 1750-1800 psi (123-127 kg/cm2 ). The nozzle tip should remain dry without an accumulation of fuel drops at spray holes.

NOTE: DO NOT  wipe injector tip with fingers. This will draw fuel through injector orifice, producing a false leak.
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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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