We have a newly acquired 2005 JLG 400S s/n- 0300084932 with a very rough idle. At start up the machine surges up and down from about 900 rpm's to 1200 rpm, then even when a function is applied and the rpm's increase the engine still surges up and down (rpms) Any idea on how to fix this issue? Thanks.
If it has a duetz engine check the fuel return lines. They are rubber with fabric covering them. If they have a pin hole anywhere it will cause this problem.
Thanks for the reply barklee. It does have a Deutz engine. I'll check the fuel lines but don't think I noticed any signs of a fuel leak.
Another thing to consider would be the electronic throttle control. I have had one of those act up and cause similar issues. I have no idea how to check one, i just swapped one off of another machine and it corrected the problem. It should be mounted on the back side of the engine toward the front cover above and right of the fuel pump. This would not be the actuator type with the linkage btw.
That's what I was thinking. A Deutz engine should have an ADDECO throttle controller with a cable. I've never seen and ADDECO cause one to lope up and down. Yes, seen plenty of that on gas engines with a Precision Governor, but not on an ADDECO. Again, I don't know for certain what the problem is, but being a diesel, the first thing I would do is verify good fuel supply. A diesel that isn't getting constant fuel supply will lope up and down, especially under load.
This is the part that i had in mind. Throttle actuator. http://www.ebay.com/itm/Fuel-Actuat...Deutz-F3M1011-2011-F4M1011-2011-/171162507486
Just looked in the parts book and if you have engine option F3M2011 it should have this throttle.
That's the fuel shutdown solenoid barklee, that's not the throttle actuator. The throttle is controlled by an Addco actuator and the actuator is controlled by a controller module. Unless it's different than the JLG's with a Deutz 1011 that I've worked on it should have a throttle controller that looks like this.
Granted, if the shutdown solenoid isn't working properly, doesn't pull fully into the run position, it will make an engine run erratic or not at all, maybe like the case you experienced.
That part actually runs the throttle. There is a plunger inside the engine and that little ear on there strokes it with three different positions. We have had to replace these when they get weak because they will jump from low to mid throttle constantly and it sounds like the engine is loping. I was told that most guys are now installing an inline bosch relay to ensure the voltage so there is a consistent flow to the throttle.
I might be mistaken but I don't believe our engine has that Addco actuator.. It does have the throttle actuator that barklee posted and we actually did a test on another machine we have, we unplugged the small cable behind the actuator to see what it did but the machine idled and revved up normal with or with out the cable plugged in.. so that led us to believe that something else is controlling the throttle/idle..
Btw fuel lines are good and the inline fuel filter looks clean/new so it should be getting the proper fuel.
I would verify that you are getting consistent voltage to the regulator. If you are not, JLG sells an inline bosch relay for this reason
Sounds like you fellows got a handle on it, carry on. :drinkup
Forgot to update this, yes the problem was the throttle actuator. Appreciate the help!
Good deal. Not a cheap fix but at least it's up and going again.
Anyone know partnr on this relay? I have a similar problem on a 800aj. Put a new regulater in but no diffrence. Changed all fuellines, starter, alternator and groundmodule. My machine will not always start, engine cranks fine but wont start. Think the regulator dont get enough volts sometimes. I tried to put a 6V external battery on regulator When it runs and then i get a stable idle.
this may be throwing out a simple check but do you have a jlg analyzer? I have seen a boom or 2 with a surging idle and it had thrown out the engine model in the setup and still ran, I had to reset it to a deutz engine and then it worked fine.