Part Verification

Why part verification matters

A wrong injector on the shop floor is an expensive mistake. The replacement part may physically fit the clamp but fail at rail pressure within 200 km, or it may run but burn 8% more fuel than the original. Three physical checks — control valve stamping, nozzle code stamping, and injector length / sealing washer OD — confirm the part you received is the one the engine actually needs. A fourth check, the post-install leak-back test, confirms the part is functional after installation.

Check 1: Control valve stamping

Remove the electrical connector cap and look for a 9-character code stamped on the solenoid body, just below the connector pins. The code follows the pattern F00VCxxxxx or F00RJxxxxx. Compare it to the engine family landing page on /by-vehicle/; the expected code is listed under each engine family’s spec table.

  • Match: the replacement part is calibrated for the same rail pressure range as the engine platform.
  • No match: do not install. Two injectors with the same connector geometry can have different valve codes for different rail pressure ranges; using the wrong one will trigger P0231/P0232 rail pressure faults within 100 km.

Check 2: Nozzle code stamping

The nozzle (the bottom end of the injector that enters the combustion chamber) carries a 9-character code beginning with DLLA. The stamping is typically on the hex face just above the nozzle tip. Compare it to the engine family spec page. If the engine family page lists “not publicly disclosed — verify by physical inspection”, you are verifying against the original part’s stamping, not a published reference.

  • Match: spray pattern, hole count, and flow class match the engine’s combustion chamber geometry.
  • No match: the new injector may look identical but have a different spray cone angle. Wrong spray pattern = poor atomization = soot buildup + P0243 / P2463 fault within 1,000 km.

Check 3: Injector length and sealing washer OD

Measure the overall length of the new injector from the solenoid face to the tip of the nozzle. Compare to the engine family spec (typically 134 mm to 168 mm depending on platform). Measure the copper sealing washer OD at the nozzle tip with calipers (typically 14 mm, 16 mm, or 19 mm). Both values must match within ±0.5 mm.

  • Length off by more than 1 mm: hold-down clamp will not seat correctly. Either the body sticks up too far (interference with the rocker cover) or sits too low (compression loss).
  • Washer OD off by 1 mm or more: combustion gases leak past the seal. Engine runs rough on that cylinder within 200 km.

Check 4: Post-install leak-back test

After installation and rail priming, run the engine at idle for 2 minutes and measure the return flow from each injector. Use a graduated cylinder on each return line. Acceptable leak-back rate for most BOSCH CRI/CRIN applications:

  • < 50 mL/min per cylinder at idle (~800 bar rail pressure). All four cylinders within spec.
  • One cylinder > 100 mL/min: stuck valve seat in that injector. Replace.
  • All four cylinders > 50 mL/min: SCV on the CP pump is failing, not the injectors. Diagnose the rail pressure system first.

Common verification pitfalls

  • Reading the wrong stamping: the connector cap has a 4-character harness code, the solenoid body has the 9-character valve code. They are different — match the valve code, not the harness code.
  • Skipping length measurement: catalog images lie. Two sister SKUs may differ in length by 4 mm; the image looks identical.
  • Reusing the copper washer: the washer takes a set after one heat cycle. Always install a new washer.
  • Not torque-cycling: the leak-back test above should be done after a 30-minute idle and a 15-minute cool-down, not on a cold engine that has just been primed.

Tools you need

  • Digital calipers (0–200 mm range, ±0.02 mm accuracy).
  • Strong light + magnifier for reading the valve and nozzle stampings.
  • Graduated cylinders (10 mL and 100 mL) for the leak-back test.
  • Fresh copper washers matched to the injector model.

When to send the part back

  • Any one of the three pre-install checks fails.
  • Leak-back rate > 50 mL/min on one cylinder.
  • Packaging seal broken or part shows signs of fuel residue.
  • The connector does not click into place before tightening.

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