5-101.bk Page 67 Friday, March 17, 2006 11:05 AM
200 BENCH PROCEDURES [222 KG] INJECTOR NOZZLES
Nozzle Cleaning
1991 and later MACK E7 engines require different fuel injection nozzles, nozzle holders and nozzle holder assemblies than previous E7 engines.
When servicing nozzle holder assemblies, cleaning of nozzle tips may be necessary. Special care must be taken when cleaning nozzle tips to avoid damaging nozzle spray holes.
These later nozzles (with eight spray holes) are a Valve Covering Orifice (VCO) configuration and are hydroground for proper fuel flow and atomization.
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Preferred cleaning method: ultrasonic cleaning
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Acceptable cleaning method: brass brush/ wire wheel
ULTRASONIC CLEANING METHOD Nozzles used for 1989/1990 MACK E7 production engine models feature six spray holes and are not hydroground. These parts are not interchangeable with eightspray-hole nozzles used in 1991 and later engines. Refer to the following engine tune-up publications for pertinent E7 specifications. 5-301 ............................. 1989 5-302 ............................. 1990
Ultrasonic cleaning units such as J 29653-A, use sound waves or mechanical vibrations, approximately 55,000 cycles per second above human hearing range. Sound waves are generated by the transducer, which changes high-frequency electrical energy into mechanical energy.
The nozzles will be damaged if a steel-wire wheel is used for cleaning. Damage can also occur if an improper size and/or speed of brass-wire wheel is used.
5-303 ............................. 1991 5-304 ............................. 1992 5-305 ............................. 1993 5-306 ............................. 1994 5-307 ............................. 1995 5-308 .................... 1996/1997
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