Detroit Diesel — Check Engine Timing
Testing & diagnosis · Gear Train and Engine Timing
From a Detroit Diesel service manual — check it applies to your exact model before use.
Before you start
- If the crankshaft pulley retaining bolt has loosened, tighten it to 450-500 lb-ft (610-678 N·m).
Procedure
- Remove one valve rocker cover and discard the gasket.
- Select any cylinder for the timing check.
- Remove the injector at the cylinder selected.
- Slide a rod approximately 12" long through the injector tube until it rests on top of the piston; place the throttle in the no-fuel position and turn the crankshaft slowly until the rod reaches the en
- Remove the rod and turn the crankshaft opposite the direction of rotation between 1/16 and 1/8 of a turn.
- Select a dial indicator with .001" graduations and a spindle movement of at least one inch; provide an extension.
- Mount the indicator over the injector tube and check the spindle is free in the injector tube.
- Attach a suitable pointer to the engine front cover with the outer end extending over the top of the crankshaft pulley.
- Turn the crankshaft slowly in the direction of engine rotation until the indicator hand just stops moving, then until it starts to move again.
- Set the dial indicator to zero; turn the crankshaft approximately .075" in the direction of rotation, then rotate in the opposite direction to .050" from the zero setting.
- Scribe a line on the crankshaft pulley in line with the end of the pointer.
- Turn the crankshaft opposite the direction of rotation through the point where the indicator stops to approximately .075" from zero, then rotate back to .050" from the zero setting.
- Scribe a second line on the damper in line with the end of the pointer.
- Scribe a third line halfway between the first two lines (this is top dead center).
- Remove the dial indicator and rod; install the injector and adjust the valve clearance and injector timing.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- In time: indicator reading .306"-.326"
- Retarded one tooth: .268"-.288"
- Advanced one tooth: .337"-.357"
Source: Detroit Diesel service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.