In Mexico I searched for Cummins as well as truck mechanics around Puerto Vallarta. Not much listed. Calling shops and asking questions could help. Truck drivers and bus drivers might have ideas. There are lots of excellent mechanics with proper tools all over Mexico - finding them can be more difficult than in the states. Here are some places I found listings online . . .
Truck = camiones , camione , camion
Repair shop = taller
Mechanic = mecanico
Parts = refacciones
Cummins Alesso Occidente
Periferico Nte 10176 Y 10240, Colonia Residencial Plaza Guadalupe
Zapopan, Jalisco 45047
Mexico
Phone: 52 33 31256051
Taller mecanico de camiones Puerto Vallarta Jalisco
http://www.seccionamarilla.com.mx/resultados/refacciones-y-accesorios-para-automoviles-y-camiones/jalisco/puerto-vallarta/1
https://plus.google.com/+FrenosYClutchMedinaPuertoVallarta/about?gl=us&hl=en
http://www.seccionamarilla.com.mx/informacion/taller-mecanico-el-tapo/refaccion-camion/jalisco/puerto-vallarta/3595132#
ALSO TRY calling Green Angels hotline at 078.
