Fit LML & LGH 6.6L 2011-16 HPCR Duramax Diesel Injector Cap Block-Off Tool 16MM

Duramax Injector Block-Off Tool fits 2011-16 Chevy / GMC Duramax (LML and LGH) 6.6L

The tool is a "must have" for anybody who works on Duramax LML/LGH common rail fuel systems. 

When a Duramax common rail engine will not start, the first thing to check is fuel rail pressure. 

If the pressure is less than 1,888 PSI one possible cause is a defective injector that is returning excess 

fuel back to the tank. A return flow volume test will verify if excessive return flow is the problem. 

This cap is then used to identify the individual cylinder that is at fault. The injection line is removed for 

one cylinder at a time and the cap installed on the fuel rail in place of the injection line. When the cylinder 

with the offending injector is capped, the rail pressure will rise and the truck will start. In some cases it 

can be highly advantageous to have multiple caps, because several injectors that return slightly too much 

fuel can have the same effect as a single injector with extremely high return flow. The injector block off tool 

can also be useful for diagnosing engine knocking sounds that may be attributable to an injector or a single 

cylinder problem particularly on engines where this capability is not available through the scan tool, or 

a bi-directional scan tool is not available.At least one of these would also be a great addition to the glovebox 

kit of every Duramax owner. When an injector malfunctions on a common rail engine damage to a piston or 

cylinder can occur very rapidly. When a common rail engine begins to misfire and blow excessive white smoke, 

the owner is highly advised to turn the engine off and call a tow truck to prevent major engine damage from occurring. 

An alternative would be to temporarily cap the injector for that cylinder for a short period.

 When working on high pressure fuel systems, always remember to read appropriate factory service information, 

use common sense, and above all, WEAR SAFETY GOGGLES to protect yourself!