ISX 600 Engine brake

[Unilevers]

there is a setting in the ecm for jake delay - if it is set to zero they should come on immediately.

under the cover there are 2 solenoids and a harness, they are very forgot about pieces. If the solenoids are wore (fairly certain they are) they have a delay to them. if the jake rockers themselves are wore, the jake can do funny things. if the harness is kinda bad, it can cause jake delay. all these need to be checked by someone who has experience in these. this is fairly common - the jakes should be instant without delay if the delay is set at 0. How much boost does it build under full jake? that explains alot also.

one last thing to check is the oil and sludge buildup in the rocker drillings themselves. if they are plugged up or the wrong oil is used jakes will be delayed aswell - just food for though