Detroit Diesel — Test #2: Percentage of Fuel Delivery for a Smooth Idle
Testing & diagnosis · Fuel injection system
From a Detroit Diesel service manual — check it applies to your exact model before use.
Procedure
- Operational range for this test: from -3% (negative) to 3% (positive); identify the cylinder with the biggest absolute value.
- For highest positive: check torque at all thrust bolts (45 N·m [33 lb·ft]) and run the test again.
- Swap the injector nozzle holder and transfer tube with the cylinder closest to zero; if the highest result follows the holder, replace the nozzle holder.
- Return both nozzle holders and transfer tubes to original positions and run impact delay time and compression test routines.
- For lowest negative: check opening pressure of the nozzle holder; if lower than 275 bar (3989 psi), replace the nozzle holder.
- Run a compression test using DDDL 7.0; readings must be 75% or higher.
Tools required
- DDDL 7.0 Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Thrust bolts 45 N·m (33 lb·ft)
- Opening pressure minimum 275 bar (3989 psi)
- Compression 75% or higher
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.