MP7 injector cups @ 114,000km

[j_martell]

Had been having sporadic starting issues, sometimes when warm and after shut down, sometimes cold (first start in the morning). Very random, but only once and a while. Then, last friday, i had one of those days, shutting down at each site for some reason or another, and everytime she didn't want to start. So, called the boss man, and told him it was near oil change time anyway, and with two rain days coming, he said take it in and have them look at. The next day, we get a call saying the injector cups on 2 need replaced and they wont have em for a few days. Then they say they're gonna do all six because its under warranty still, but they will have the truck for 2 days. so, as a fairly new driver, i wanna know what these cups do, and what would cause them to "take holidays". Any input is appreciated.

[Challenger]

Injector cups are a big problem. Its safe to say every Mack and Volvo will have the problem. The injectors sit inside the cups. Basically the injectors move very slightly and compression leaks pass the tip and gets in the fuel system causing hard starting and and low power.

Even if you werent under warranty, all 6 cups should be replaced.

[j_martell]

Thanks challenger

[bbigrig]

Sounds familiar...... Maybe Volvo/Mack need to start installing auxiliary O-rings like in Detroit 50 and 60 series engines. For those unfamiliar, Its a thick rubber O-ring installed between the upper of the injector cup to seal against the surface of the injector body. This O-ring is a back up for if the combustion gas that can get between the injector tip and cup sealing area like the MP's. That O-ring makes a huge difference as Detroit use to have the same MP8 is on its 3rd set of cups and 1 of my 2013's at 20,000kms had all 6 cups and injectors done.