Jake Brake works at random

[Supermutt]

Ok guys I know there have been a number of Jake brake topics as of late. But none seem to fit my issue. Looking for help in narrowing this down. 
  The Jake will work intermittently when it feels like it. When it does it works strong. Some times it will come on like it has low voltage. Almost like it’s trying but not quite. 
  With the Jake switch on both relays feel like the contacts are chattering away but no Jake. 
  Oil pressure is great. 20 plus hot at idle. Then goes right up to 50-60 off idle. 
  So if I turn the Jake on like I just did it was delayed. I then went and run a jumper from the alternator to the head and instant Jake (strong) would have stalled the engine. 
  So could this be the relays ?  Should they be clicking away non stop with the switch on ? 
 I don’t think it’s a switch but anything is possible. 
  I recently changed injectors and when the valve covers were off I pushed on the solenoid’s and instant Jake. 
 For the record I had this issue prior to replacing the injectors. 
  The truck is a 1996 DM688S, e7 350, full mechanical.

 Thanks for any help !

[Joey Mack]

What year engine?? And did you put a volt meter on the Jake wires at the solenoids to see the voltage? 

[Mean Green]

Sounds like low voltage or possibly a bad switch somewhere it voltage should run through every thing then to solonids so dash switches clutch switch and switch at pump should be checked

[Supermutt]

Engine/Truck is a 1996. No I did not check voltage. But I will.  Thank you ! 

[Joey Mack]

There is a spring loaded switch at the clutch pedal arm, and a micro switch on the throttle linkage at the injection pump..

[Supermutt]

Joey do you think either of those switches could cause low voltage ?  In my experience they either worked or didn’t. Open/closed. At least on the e6. I see the pump switch is a bit different on this e7. Think there is a diode there to. 

[JoeH]

My Jake does the same on my 95 e7-350. Always get at least one head working on high, usually don't get the "low" setting head working ever.

[Joey Mack]

Dirty contact inside can cause resistance, and the one at the injection pump is always subjected to dirt, oil, and heat..  just something simple and 🆓 to inspect..  I have found bad throttle switches on dump trucks, that were affected. Can you post a picture of the throttle switch?

[Supermutt]

Thanks guys ! I appreciate it. I will post a pic of the pump switch 

[Supermutt]

Here’s a pic of the pump switch. 

[Supermutt]

Front head engine of Jake on 12.38v.  Engine running 13.6v. Jake worked that time. At idle stalled it out almost instantly. This things going to drive me batty. 

[Supermutt]

Ok. Now at idle the Jake started to sputter, like try to come on for half a sec. Checked the voltage on front head while it was doing that and it’s all over the map. 14,11,7,12,3 etc 

[Supermutt]

Also as I said earlier if you turn the Jake on and put your finger on the relays at the same time you can feel them chattering away even though the Jake is doing nothing. 

[Joey Mack]

Supermutt..  those engine brakes are ''People Controlled''  not ''Computer Controlled''  if it is running and the switch is on the engine brake will be on and the engine will stumble, unless you do 1 of 3 things,,,   lightly rest your foot on the clutch pedal,,, lightly hold the throttle down, -or- just shut the dash switch 'Off'...     Im having some fun here..  dont know if you know that about this set-up?  Glad you are here..   Jojo

[Joey Mack]

That throttle switch is adjustable, if you need to set the ''sensitivitey''. 

[Supermutt]

Joey I sent you a message. 4:10mtn 6:10 East

thanks 

[mechohaulic]

I  had a number of different jumpers(pigtails ) made for things such as jake switches. short wires with different ends . the jake switches where threaded terminals with short spade terminals many times. pull the wires off switches and put a jumper  to by-pass the switch (es). use dash switch for control-on/off.  process of elimination. problem exist  -switches good. of course in the day; wiring was much simpler . not all the relays, modules  etc. 

[Joey Mack]

I think a valve adjustment is in order.  Stay with the procedure that Mack lays out in the book.  We can guide you..  also, many guys dont look at the valve yokes on the 4-valve engines...  they HAVE to be set..  You Can, Remove the jake heads,( this will allow you to inspect the top end).  Or you can leave them installed..  and get (2) .010'' feeler gauges..  put one under each end of the bridge and press down on the bridge, and feel the drag on each feeler gauge,  adjust the screw until they are evenly dragging..  no need to rotate the engine for this step..  then put the jake heads back on and run the valves by the book..   

Edited August 6, 2023 by Joey Mack
More content needed

[Joey Mack]

here are some pics from my E-7 book..  

[Joey Mack]

the camshaft number is the real deal when figuring engine brake lash..  

[Supermutt]

This is good stuff Joey ! Thank you for taking the time and sharing. As well as everyone else that provides help ! 

[Supermutt]

More issues. Just pulled the boost hose off the turbo looking for causes of bluish smoke and some oil consumption. 
  So I don’t think what I found is good. Sooty, black and tar like on the compressor side of turbo. Not like some I have seen soaked with oil. Here are some pics. Could this be enough to cause on and on bluish smoke all of a sudden. 
  Boost only hits 20-25 max with the pump opened up. Should hit 30 +++ in my opinion 

Almost looks like exhaust going into the compressor side ? 
Will look at intake tomorrow. 

[Supermutt]

Also getting increased blow by in the last 2 days. 

[Joey Mack]

it doesnt look all that bad..  pressure test the CAC.. Cracks appear at the top right corner and run down the weld where the viens meet the side tanks..   usually on the front side.....   

[Supermutt]

I was thinking I shouldn’t see or have any gummy tar like residue on the compressor side. On my hands it was tar like.