Could anyone straighten me out on how to tell if the engine in our road tractor has an engine brake? We recently bought a 1994 Peterbilt 378 that originally shipped with an engine brake but has had the original engine pulled and replaced with a motor from a crashed out truck. Best we can tell the truck now has a 3406B installed and think it originally shipped with a 3406C based on the year and the cabling in the truck not in use but present. We have the switches for the brake but it is not currently working according to the driver. So the question becomes how to tell if the engine we have now is equipped. Maybe I am being dense here, so if it's a super easy tell, forgive my ignorance.
Go to the passenger side of the engine. Look at these two pictures, one has jakes, the other doesn't. You should see the narrow plate that has the jakes in them with the wire hook up if it has them. You may need to replace some parts internally if they haven't been used in a long time. Top picture is no jakes, second picture has jakes.
I don't know the answer but it sure not a dumb question. I have a 3406b in my dump truck at work and I use the heck out of that thing.
If you don't have them and want them, you should be able to find a used set and install them, or have them installed.
Even used are expensive {Jacobs model 346}. Jacobs also built a model called Super Jake model 349, updated to 349A IIRC. There is also the Pacbrake model. If you do need jakes make sure and get every part and piece. But buy a tune-up kit and rebuild them before installing and test the solenoids.
Good news, we have jake brakes on the engine. Just don't know why they aren't working. I feel super dumb though. Jacob is stamped right onto the head. Here is the next question. This truck was built in December of 1993. Best I can tell this truck shipped with a 3406C. We know that what's in the truck now is not the factory engine because the guys we bought it from told us they took an engine from a totaled out truck and moved over to this truck. Looking at the part numbers on the pump this is a 3406B. Based on the pictures and unused wiring can you guys tell if I am correctly assessing that this is a 3406B? I cannot find anything else to reference on the motor to tell me. The tags, plates or embossed numbers are all MIA best me and the driver have been able to tell.
This was a great reply and helped me tremendously in identifying the exhaust brake being present.
While i'm far from an expert, that motor looks fairly similar, but there is quite a few variations compared to my 92 with 3406B. Is there not a plate on the engine identifying it?
With it idling jump some powet to the pin that powers the jake and see if they pop it they do you got electrical problems judging by the wiring in the photo it's probably it
It's a B--Look on right rear side of engine block about 4" below cylinder head. There should be a engine serial number stamped in block.
So if it was a 3406 PEEC controlled 3406c engine, it had a electronic throttle pedal, and some electrical controls on a mechanical injection pump. The B will have a manual rod and spring returns on the injection pump throttle control. Which is how yours is set up now- a manual throttle control. From what I've read and heard from guys more familiar with them than me- the peec system was troublesome, and few parts were available for them even when newer. Most engines were "reconverted" back to a B model style injection pump, by replacing the rear of the injection pump with a B model manual control section, or simply replacing the whole injection pump. And then finding a manual pedal and linkage and doing away with all the electrical. Which would explain all the extra wiring you have tied up on the drivers side of the engine. Rather than ripping out the wiring that was unused, they just tied it up. What I can't see is a switch on the b model injection pump in your truck- for controlling the jakes. There should be a small switch on the throttle arm or on the pedal that allows the jakes to come on only when the arm is in idle position. If you step on the throttle, the switch pulls the 12v away from the jakes. You should also have a switch on the clutch- so that if the clutch gets pushed in, the jakes go off. This could be the reason your jakes don't work- they never finished the extra wiring needed (adding the switches), so they just left the jakes unhooked. These pics might help- this is toward the front of the drivers side of the engine, should be right around the height of the frame rail. Here's pictures of a peec and non peec injection pump. The difference is in the back of the injection pump. Peec is first picture, non peec is second.
I have all the peec and mechanical books if you need any information ill look it up
There also two different types of governor housings and jake switches for the B model.