M816 Throttle Creep

[wcuhillbilly]

Ok, there is probably something missing or I need to replace a spring...... This has been an issue since I got it back in OCT. but has become annoying when its just me running the wrecker/throttle/load/running on and off the truck. I know idleing is a no no with the NTC 250... Cummins mechanic told me to they like 1100 when using a hydraulic load like our wreckers. I just cant keep it at 11-1200.
Basically I can set the dash throttle lock to about 4 or 5 clicks out and it will marginally hold the throttle at 5-600rpm but if I go for the 5-6 clicks then it will bypass 600rpm and start climbing all the way to 1800-2300.
I can set the rear throttle control a couple clicks and it will marginally hold the throttle around 800rpm but it will start climbing as well if not closely monitored...

Case in point the other nite I was pulling a 4bt cummins out of my enclosed trailer and moving it to the garage. phase 1, set the dash throttle and start unhooking the boom, as Im starting to get all the prop rods down the throttle takes off and tachs out. Ok,,,, so the dash lock isn't going to behave, closed the dash lock and set the rear throttle control (cable function is free of obstruction and tension feels fine) I don't need full rpm thus I was hoping it would nest at 800rpm. shortly (as in about 2-3 min) it was back up at 1800rpm and I am forced to climb back up and monkey with it to find a sweetspot..
Now once it was in a good behaving position (as in not at 2300rpm) I would feed the cable out and the engine would pull down, (mind you this was with no load on the hook, and a 4bt only weighs 6-700lbs) once I was off the control the engine rpm was right back up again....
So Im stumped and as it is icy cold and raining outside Im not wanting to go poking around at the moment.
Yes the tcase was in neutral, parking brake set, and trans in 4th.

 

[R Racing]

Your either sucking air through bad fuel lines. Fuel selector switch. Or your injection pump is going bad. I'm leaning towards fuel lines as both my m813 and m816 both did it until I replaced them.

 

[doghead]

Are you setting the auxiliary governor?

Or are you simply trying to hold the throttle up with the throttle cable?

The later never works.

 

[dmetalmiki]

One would think you would have the same issue if you "sat" on a steady foot pedal also?.

 

[Floridianson]

Yea the Cummins will allway idle up if you don't have the rear controls in use.. As DH said you need to engage the secondary Govener buy putting the rear controls in play not just the pto lever in the cab behind the seat. Then useing the rear or forward throttel control the motor should idle up and not go over the set RPM needed for hoist / winch useage.
It should be in the TM's but it would be slect correct transmission gear, transfer case netrual, ingage in cab PTO. Then to the rear. Disengage clutch useing rear control and slect Hyd. controls and ingage and then disengage clutch. Then increase the rear or forward throttel cable control and the secondary govener should be in play.
If not then you need to climb under the truck and look for the linkage the controls an air valve and lets the air go to the aux.governer and try and track down why the air cylinder is not engageing or pushing out to control the aux. Govener.

 

[73m819]

I REMOVED the hand throttle on the m819 and installed a veneer cable, once the truck is warm, I can adjust the rpm right to a gnats eye lash, where ever I want it, I most times run between 750 and a 1000 rpm,

 

[Floridianson]

The only outher thing I was thinking was if someone replaced your PT with one that does not have the Aux.governer?

 

[wcuhillbilly]

Well,,,, i have been using the rear controls. Tcase in nuetral, clutch in, engage pto behind seat, select 4th in trans, release clutch, climb out and engage clutch via johnny bar, engage hydr lever, release clutch via johnny bar, attempt to set throttle with hand throttle next to johnny bar, ratchet it up about 2-3 clicks-nothing,,, hit 4th or 5th click and it takes off for 2300rpm. If there is a throttle govner for the aux controls i have not found it

 

[Floridianson]

The Aux. governer is on top of your PT and has an air cylinder on it. If I rember the linkage is under on the right side comming from the back just about in line with the fuel tank. Then an air line going to the PT. When you ingage in the back it should be switching the air valve up under. My Aux. Govener is set about 1100 rpm. I will try and take a pic tonight.

 

[doghead]

Post a few pics of your injection pump.

Top and towards the rear.

A look through the parts TM, should help you see the parts we are referring to.

You need to open the hood while operating it and see if your aux gov is operating.

 

[Westech]

Sounds like a bad rubber fuel line from the tank. On the 800's the line leaks air and will idle low for a long time until the air is bleed out and then she takes off. Mine was doing the exact thing and I replaced the line and filter (with new can gasket) and poof fixed.

 

[73m819]

I have the rpms creep up as the truck heats up, the rpm goes up, once the ip is at operating temp, I can set the rpm and it stays where I put it, my m819 has done this since I have owned it (10 years)

 

[Floridianson]

Sorry about the hazey pic but it is just about where I told you the valve is. Right side under by the fuel tank. Then your PT should look like this with the Aux. governer on top. You can increase or decrease the Aux governer to what the TM's call for in RPM. As said mine is set for 1100. You can change it buy the stop bolt attched to the IP. so out towards the cab would increase run it in and it will decrease the governed RPM.
When the Aux. governer is engaged the motor can not go over the set RPM. You could jump in the truck and take off with the peddel to the floor but it will only go to set rpm.

 

[wcuhillbilly]

Thanks for the pics.....
Ok,, I don't recall seeing any air cylinders near the Inj Pump. Just a bunch of cables or push/pull sleeve wire style cables, and a few old return springs. just whats in your first pic
So I guess that part got scrounged some time back. I will look on the truck tonite providing I can get the hood up as there is a fresh 4" of snow overnite. I can try to get some pics but don't know if my phone will let me up load them as I will be away from the computer for the next 3 days.

PS.... The fuel lines have been replaced with JIC and parker line. Don't think the selector valve has been rebuilt, and the primer plunger does leak a tad. any clues how to rebuild it????? And on that note,,, the fuel pressure guage works while pumping but is it supposed to show pressure while the engine is running,,, it currently does not...

 

[Floridianson]

No the fuel pressure gage should not show PT pressure just pump up primer pressure. You would peg the gage if the PT went to full pressure.

 

[wcuhillbilly]

Found part of the problem. The cariage bolt has rattled loose enough to fall below the piston on the bimbi cyl. The bimbi cyl tip is threaded, is there a special end that needs to be there, cant really tell from the pics???

 

[doghead]

Here's the picture page from the parts TM.

There is no end on it.

 

[wcuhillbilly]

Thanks... Doghead, I haven't had time to fix the carrage bolt jambed under the air cyl yet..
Your black lab looks like one I had as a kid... good dogs...loyal to a fault and hard to see at nite when your stumbling your way to the outhouse