Community Forums

offtosleep · 01-20-2019, 08:37 PM

Over the last month or so, I've noticed my Jake Brake working intermittently. Today, it nearly became a major issue that could have harmed my family.

We live in Arizona and took the kids to a soccer tournament. I was traveling through Salt River Canyon (20 miles of 6-8% grade). The brake wouldn't come on when I needed it or if it would, the instant I left of the foot switch, it wouldn't engage the next time I needed it.

When I looked into it before and talked to Jacobs, there are three "triggers" the brake needs 1. The foot switch depressed 2. The transmission to be in full lock-up and 3. A signal from the TPS (throttle position sensor) that the accelerator isn't being depressed.

Months ago, I took the foot switch apart and its a very simple momentary switch. Tested it. Worked fine. The inside of the switch looked pristine.

I then made a jumper wire at the engine bay and tested the solenoids at the heads/valve covers. It worked perfectly. I also tested the relay in my fuse/power distribution bay as well as the fuse associated with it.

If the TPS is involved, I'd be surprised as I have ZERO other fuel related issue including acceleration/throttle response, power, stutter, etc.

I also have zero issue with the tranny. Its always been serviced, no issues shifting, etc.

I'm hoping you smart group of people can point me in the right direction.

Fiesta48 · 01-21-2019, 06:31 AM

Newer Retarder brakes are not intended for every stop. Only when you really need it on more serious downgrades.

Unplanned Tourist · 01-21-2019, 07:34 AM

Plug in an ECM reader and watch the throttle position reading. It has to register 0% or the ECM will not let the engine brake turn on.
A small buildup of dirt or whatever around the throttle pedal can cause it to not fully return to the 0% position. This is the first and simplest thing to look for.
Happy Glamping.

Crop Duster · 01-21-2019, 07:56 AM

Quote:

Originally Posted by Unplanned

Plug in an ECM reader and watch the throttle position reading. It has to register 0% or the ECM will not let the engine brake turn on.
A small buildup of dirt or whatever around the throttle pedal can cause it to not fully return to the 0% position. This is the first and simplest thing to look for.
Happy Glamping.

That would be too simple.

Hope it works

Ray,IN · 01-21-2019, 10:35 AM

Test the TPS with an ohmeter, disconnect the wiring and use the ohmeter to check reliability. The actual readings are not very important, what is important is a gradual , consistent increase/decrease in the readings from 0 to max and back. If the readings are jerky or erratic, the TPS must be replaced. Most any truck parts store will have a replacement.

offtosleep · 01-21-2019, 09:54 PM

Quote:

Originally Posted by Fiesta48

Newer Retarder brakes are not intended for every stop. Only when you really need it on more serious downgrades.

My coach is a 1999. It is/can indeed be used in all circumstances. I humbly disagree with you comment.

twinboat · 01-22-2019, 04:56 AM

If the throttle pedal is even slightly sticky, it could be causing your problem.

While running, press down and gently let up and see if the RPMs drop fully. Even 50 RPMs high could effect it. Lube anything that moves.

Fkrel · 01-22-2019, 06:19 PM

Quote:

Originally Posted by offtosleep

My coach is a 1999. It is/can indeed be used in all circumstances. I humbly disagree with you comment.

I disagree with that also. They quit making the N14 some time ago But it is a very good engine, Does your throttle pedal have the two switches in it you can tell by it having two different plugs at the end going up into the dash, If I remember that is a williams tps Try calibrating the pedal and see if that helps
to do this turn the ign on (dont start) press the pedal down and then up three times and then turn the ign off the pedal is now calibrated. also check the brake switch for the engine ecu this should be s seperate switch on the brake valve. The jake is controlled by the ecu and the brake switch for the jake signals the ecu and I believe the ecu tells the transmission to lock up same with the tps it signals the ecu.

Now a couple other tidbits for that engine If you develop a oil leak on the left side of the engine check the oil pressure sender they like to leak, next time you are doing maintenance on your engine check the tightness of the bolts on the cam follower boxes they like to loosen up and leak oil. If you have a mild miss and hard to center which injector check the cam follower sensor its behind the compressor into the front of the gear train, unplug the sensor and look in the plug if it has oil in it replace the sensor, they like to wick oil from the gear train thru the wires and cause a confused signal to the ecu. Good luck

slickest1 · 01-22-2019, 08:05 PM

Is your cruise control shut off? That can sometimes cause a problem with the Jake.

JMyers57 · 01-22-2019, 08:45 PM

As already mentioned, most jake brakes will not work if your cruise control is in the on position, that would be my first thing to address before other checks are made, you don’t have to drive very fast to check them.

offtosleep · 01-26-2019, 06:20 PM

Thank you for all the input. Looking into it tomorrow. Anyone have a part number for a Cummins N14 TPS?

Mr_D · 01-26-2019, 06:31 PM

Quote:

Originally Posted by Fiesta48

Newer Retarder brakes are not intended for every stop. Only when you really need it on more serious downgrades.

Yes, they are intended for full time use. Don't know where you got your wrong info from.

offtosleep · 01-26-2019, 06:32 PM

Also, does anyone have a schematic or pic of where its located?

Roadmiester · 01-26-2019, 06:43 PM

If you can get to a Cummings service center I believe they can check to see that the engine/tranny are getting the signal to apply the jake. I have heard of oil getting into the wire harness connectors and messing things up. If you coach was 10 years newer I would say your having issues with you roadside multiplex, like we did with the jake having a mind of it's own until it just quit working. However, I don't think you coach has a J1939 or a CANbus data bus, or does it? Can get very expensive chasing this problem.

Roadmiester
09 Dynasty Regal IV
45 ft., tag axle, ISM500