No throttle

[Tomas]

I have a TC1000 with a 5.9L 24V.
Engine starts and idles but there is not throttle. In other words pressing the accelarator pedal won't do a thing.
Front air reads about 40 psi and rear about 30.
I have not been able to identify any air leaks.

Is there a troubleshooting guide I can follow?

[brokedown]

Your bus doesn't want to operate below 90-100 psi. if you have an air throttle it may not work until you've achieved operational pressure. You sure won't have brakes that low!

[Tomas]

Correct. I do believe I have an air throttle.
Should I be checking for air leaks and whether the compressor is building enough pressure? Or are there other checks I should be performing?

[brokedown]

when you shut your bus off, how fast does your 30-40psi turn to 0psi? if it empties fast you should be looking for leaks. If it stays at 40 for days then the compressor is not doing its job.

[Tomas]

ok thanks. I am gonna check that.

[Tomas]

Ok I checked for leaks and couldn't find any.

The air pressure for both front and rear stays at around 30 psi for several hours before slowly dropping. If there is an air leak it is very small.

I checked the air drier and didn't find any leaks there. Same for the rear brake actuators.

What would be the next step? Check the air pressure governor? Whats the procedure for checking that? Do I remove the whole compressor with governor for that?

[Mountain Gnome]

Originally Posted by Tomas

Correct. I do believe I have an air throttle.
Should I be checking for air leaks and whether the compressor is building enough pressure? Or are there other checks I should be performing?

My 1999 TC1000 with a 5.9L 24V has an electric "throttle" pedal. But actually diesels don't have a "throttle;" there is never a restriction on the air going in. Only more fuel being added as you need more power. Are you saying the fuel pressure/volume injected into the motor at any given time is regulated by air pressure? I don't believe so. It is controlled with oil pressure.

Perhaps there is a safety feature that won't let you drive if your air is low (if yours is newer than mine) but I doubt it. I would look into the fuel pedal switch or its wiring

[cadillackid]

gnome,


some busses, generally Rear engine busses with non electronic engines had a throttle that was activated by air pressure.. the way it worked is at the pedal you have an air valve that sends air pressure back to a spring loaded actuator.. the mnore air pressure, the more that actuator essentially activated what would have been the throttle cable. if the bus air brake system pressure was not up then the throttle would fail to operate. there should not be an air throttle on a front engine bus..



being electronic this one should be an electronic fly-by-wire.. make sure the wiring connector at your throttle pedal is plugged in securely and that none of the wires have been damaged or cut.. these wires should feed into a harness going to the Engine computer.. be sure the engine computer connectors are secure as well..

-Christopher

[BlackJohn]

Not sure how you checked for air leaks.



Can you comment on that as you do have a few leaks I assume from reading this?


A spray bottle of water and dish soap is a priceless tool for chasing down leaks.
Spray down every fitting and every inch of hose, compressor fittings etc. takes some time sure but then you can make a plan to fix.

And it is fun watching the bubbles being blown.


John

[Tomas]

I only listened for air leaks by crawling under the bus.
There could be air leaks but they are very small. Like I mentioned pressure for both front and rear air tanks remain at a constant 30 psi or so for several hours. Leaks cannot be the reason it's not building pressure.

I believe the accelerator/throttle on the TC2000 and TC1000s are locked unless operating pressure is reached regardless whether it's a front or rear mounted engine. I have front mount and there is an air valve marked "throttle" on the manifold above the tanks on the access hatch by the drivers side of the bus. The line has pressure right now but only 30 psi. I presume once 90 psi or so are reached that it unlocks or activates the accelerator pedal.

[Booyah45828]

See what the pressure is in the wet tank, the gauges on the dash don't read that. Opening the petcock on it with the bus running is a quick way to tell for air flow/pressure.

After that, find the governor and see if that is stuck causing the compressor not to run.

As far as air pressure and throttle issues, as said by others, the throttle is electronic and is completely seperate from the air system. I doubt the two problems are related.

[Brad_SwiftFur]

Air systems are not terribly complex ... though they can seem to be. You have:


1. Air compressor (and it's related governor, belt/gears, pulleys, etc.) The function of this is fairly straightforward. The governor's job is basically to turn the thing on/off, typically at 90/120 PSI, respectively.
2. Air dryer (on most systems, a few may not have this). The air from the compressor goes through this. Many have "cartridges" or filters that should be changed about once a year (and rarely are). The most common symptom of a failed air dryer is a failure to build up pressure (and usually accompanied by a very noticeable hissing of air from the dryer). Some designs are proprietary to the vehicle to which it's attached, but so-called universal fit designs work just fine in their place.
3. Air tanks. You'll have at least 1 "wet tank", fed by the air compressor, and at least 2 "dry tanks". Sometimes you'll have 1 tank with 2 compartments, or any combination the builder installed. There is often a "protection valve" which will feed the dry tanks once the wet tank reaches a certain pressure. If a tank looses pressure suddenly, this protection valve maintains pressure in the other system, giving you a chance to stop safely.
4. "Everything else". Air brakes, air-ride suspension, parking brakes (also called spring brakes), air-ride seat, gauges, warning lights and buzzers, brake-pressure sensor (the one that makes your brake lights work), and, you guessed it, everything else. The vast majority of this stuff is past a protection valve, basically meaning none of it will work until the system reaches the protection pressure, typically 60-80 PSI. An air-throttle (if you have one) will be on this circuit. Usually the only thing *NOT* on this circuit is the brake pedal, parking brakes, and gauges/warnings. The brakes *NEED* to work at all times, regardless of how much air is in the system.

[Mountain Gnome]

Originally Posted by Tomas

I have a TC1000 with a 5.9L 24V.
Engine starts and idles but there is not throttle. In other words pressing the accelarator pedal won't do a thing.
Front air reads about 40 psi and rear about 30.
I have not been able to identify any air leaks.

Is there a troubleshooting guide I can follow?

What year is your bus? My 1999 TC1000 5.9L 24V will respond to the accelerator pedal with no air in the system (after bleeding the tanks down completely).

Originally Posted by cadillackid

gnome,

some busses, generally Rear engine busses with non electronic engines had a throttle that was activated by air pressure.. the way it worked is at the pedal you have an air valve that sends air pressure back to a spring loaded actuator.. the mnore air pressure, the more that actuator essentially activated what would have been the throttle cable. if the bus air brake system pressure was not up then the throttle would fail to operate. there should not be an air throttle on a front engine bus..

Christopher

Are you saying the intake tube was restricted ("throttled") like a gasoline motor has a butterfly-throttle-vavle, or are you saying the fuel injector controls were remotely air-operated? I believe the latter...otherwise why would a rear-engine need to be throttled, but not a front-engine? I totally see a remote pneumatic system for the rear makes sense....

Originally Posted by cadillackid

being electronic this one should be an electronic fly-by-wire.. make sure the wiring connector at your throttle pedal is plugged in securely and that none of the wires have been damaged or cut.. these wires should feed into a harness going to the Engine computer.. be sure the engine computer connectors are secure as well..
Christopher

Yea, what he said....

[cadillackid]

Originally Posted by Mountain Gnome

What year is your bus? My 1999 TC1000 5.9L 24V will respond to the accelerator pedal with no air in the system (after bleeding the tanks down completely).



Are you saying the intake tube was restricted ("throttled") like a gasoline motor has a butterfly-throttle-vavle, or are you saying the fuel injector controls were remotely air-operated? I believe the latter...otherwise why would a rear-engine need to be throttled, but not a front-engine? I totally see a remote pneumatic system for the rear makes sense....



Yea, what he said....

Gnome - yes air actuated throttle for the fuel pump.. the air tube is unrestricted at all times.. as you say all of a diesel's throttle control is fuel. on RE busses the distance front to back made mewchanical lionkage extremely sloppy and prone to sticking.. so using air elminated this.. the pump was the same.. but the lever which a normnal throttle cable would push / pull. was activated by an air cylinder.. the pressure in that cylinder controlled by the driver'throttle pedal up front..



-Christopher

[Tomas]

Originally Posted by Brad_SwiftFur

Air systems are not terribly complex ... though they can seem to be. You have:


1. Air compressor (and it's related governor, belt/gears, pulleys, etc.) The function of this is fairly straightforward. The governor's job is basically to turn the thing on/off, typically at 90/120 PSI, respectively.
2. Air dryer (on most systems, a few may not have this). The air from the compressor goes through this. Many have "cartridges" or filters that should be changed about once a year (and rarely are). The most common symptom of a failed air dryer is a failure to build up pressure (and usually accompanied by a very noticeable hissing of air from the dryer). Some designs are proprietary to the vehicle to which it's attached, but so-called universal fit designs work just fine in their place.
3. Air tanks. You'll have at least 1 "wet tank", fed by the air compressor, and at least 2 "dry tanks". Sometimes you'll have 1 tank with 2 compartments, or any combination the builder installed. There is often a "protection valve" which will feed the dry tanks once the wet tank reaches a certain pressure. If a tank looses pressure suddenly, this protection valve maintains pressure in the other system, giving you a chance to stop safely.
4. "Everything else". Air brakes, air-ride suspension, parking brakes (also called spring brakes), air-ride seat, gauges, warning lights and buzzers, brake-pressure sensor (the one that makes your brake lights work), and, you guessed it, everything else. The vast majority of this stuff is past a protection valve, basically meaning none of it will work until the system reaches the protection pressure, typically 60-80 PSI. An air-throttle (if you have one) will be on this circuit. Usually the only thing *NOT* on this circuit is the brake pedal, parking brakes, and gauges/warnings. The brakes *NEED* to work at all times, regardless of how much air is in the system.

Thanks for the explanation.

Let me see if I understand how its plumbed correctly. From the compressor to the governor to the wet tank. From the wet tank to the drier and from the drier to the front and rear "dry" tanks. Is that correct? I thought I saw a hose going directly from the governor to the drier but may be I imagined it. I'll check again.

Haven't taken a reading of the wet tank yet. Will do soonest possible.

Originally Posted by Booyah45828

As far as air pressure and throttle issues, as said by others, the throttle is electronic and is completely seperate from the air system. I doubt the two problems are related.

Originally Posted by Mountain Gnome

What year is your bus? My 1999 TC1000 5.9L 24V will respond to the accelerator pedal with no air in the system (after bleeding the tanks down completely).

It's a 2002.
Are you missing an "AIR THROTTLE & SUSPENSION" petcock/valve on the manifold by the front air tanks like this one?

[Booyah45828]

Originally Posted by Tomas

Let me see if I understand how its plumbed correctly. From the compressor to the governor to the wet tank. From the wet tank to the drier and from the drier to the front and rear "dry" tanks. Is that correct? I thought I saw a hose going directly from the governor to the drier but may be I imagined it. I'll check again.

Haven't taken a reading of the wet tank yet. Will do soonest possible.

No, the compressor build the air pressure, then sends it to the drier(driers are optional, most have them, a few don't). It then travels to the wet tank, which will either have the governor attached to it, or it will send a small reference line to the governor wherever it is mounted. Sometimes it's mounted on a frame rail, sometimes it's mounted on the compressor. After the wet tank, air should travel through a check valve into the primary and secondary air tanks.

The governor is nothing more then a spring loaded shuttle valve. When air pressure(around 125 psi) overpowers the spring, the valve moves sending air pressure to the compressor and air drier, shutting the compressor off and purging the drier. When air pressure to the governor drops below 100 psi, the shuttle valve closes, releasing the psi sent to the compressor and drier, allowing both of those items to work again.

[Mountain Gnome]

Originally Posted by Tomas

It's a 2002.
Are you missing an "AIR THROTTLE & SUSPENSION" petcock/valve on the manifold by the front air tanks like this one?

I do not have that valve. So you have air suspension!?!?! Lucky....or is that for another air-powered accessory? My air-ride-driver's-seat doesn't work. I wonder which system it takes air from?

Note one valve has been replaced. I need to replace another, but it won't budge to unscrew it. It is my slow leak, especially when cold outside...

[Tomas]

Yes. Leaf springs in the front and air bags in the back.

[Tomas]

Yes. Leaf springs in the front and air bags in the back.

[Mountain Gnome]

It struck me yesterday that maybe you have a blown fuse. There is a hidden fuse panel on the front-side of the dash-display, behind a screw-on cover with 4 screws on my bus. But none seem related to your issue.