CM 870 JAKE BRAKES

[tree98]

I don't know the answer to your question but I can tell you that your absolutely playing with fire using the Jake on its highest setting on a rebuilt engine that the valves haven't had time to wear in. People have grenaded there engines that way. You should wait about 40k-50k miles.

[Rawze]

first of all ...
JAKE SHOULD NOT BE USED ON ITS HIGHEST SETTING FOR THE FIRST 50K MILES until the head wears in and you do a second overhead valve adjustment. - I HAVE LITERALLY SEEN myself,.. where people have completely destroyed their engines by trying to run the engine brakes on high during wear-in, after a fresh inframe.

Next, as a reminder ...

Its an ISX. Most all of them ONLY HAVE 2 JAKE SOLENOIDS!. One for the front 3 cylinders, and one for the back 3. - The THIRD STAGE engine brake setting simply uses TURBOCHARGER to spool it up hard, supplementing the engine brake strength (seen as up to about 28-psi boost at the intake during braking).


It is actually fairly rare to have a CM870 with 3 engine brake solenoids. Only some of the very oldest CM870's had the 3 solenoid setup, and even then, most did not. Hence there are some factory ecm programs that are meant to drive 3 solenoids. Most all the other factory programs however do not have support for 3 solenoids, and therefore do not use 3 solenoids.

For all anyone knows, you might have a mess on your hands, trying to make a 3rd solenoid work that is not supposed to be there? ...or the wrong program in your ecm for the ser#?.

Also, depending on the ecm part#.. The ecm itself may not even have internal driver support for a 3 solenoid because it is fairly uncommon.

[Catman]

I thank you for getting back to me so quickly. I did read about not using Jake on high for the first 50k miles and will take caution. My engine does only have 2 solenoids. The ecm is only sending power to the rear Jake solenoid. I never get power to the front solenoid no matter what I do. Just two weeks ago all three positions on the Jake switch were working and now I only have low Jake. I am not getting any fault codes for the Jake system only a active EGR fault.

[Catman]

I was able to use a Insite 8.9 to hook to the truck last night. It was also showing all switch status appear to be operating properly. The ecm is showing only the rear solenoid being activated.