1985 Chevrolet Impala 5.0 HFACTORY OEM SERVICE PROCEDURE

Injection Timing: Adjusting

  1. Shut off engine. Note relative position of marks on pump flange and pump adapter. Loosen nuts or bolts retaining pump to the adapter. Rotate pump to left to advance timing and to right to retard timing. Width of mark on intermediate adapter is about 2/3°. Adjust timing. Tighten bolts to 35 ft. lbs. (47 N.m).
  2. Start engine and recheck timing. Reset timing if necessary. Adjust throttle linkage assembly on V8 engine. On V8 and V6 engines, reset fast and curb idle speeds. See appropriate article in TUNE-UP Section.
    NOTE: Wild needle fluctuations on timing meter indicate a cylinder that is not firing properly. Condition must be corrected prior to adjusting timing.
  3. If after resetting timing, timing marks are far apart and engine does not perform correctly, dynamic timing still could be incorrect. A malfunctioning cylinder can cause incorrect timing.
  4. If so, check timing on alternate cylinder. Timing can be checked on cylinders No. 2 or No. 3 on V8 engine, or No. 1 or 4 on a V6 engine. If timing difference exists between cylinders, try both positions to determine which timing works best.
Chapter Navigation
Return to Chapter: Injection Timing
Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.

Shop Manual-Ready ToolsCompare Repair QuoteQuote Shield Pro

When to See a Mechanic

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.