I need help. I have a JLG40H, it drives fine ,lifts fine and swings fine. My problem is it suddenly will not pull up on my trailer. The engine lugs down and feels like it is remaining in high wheel speed. It shifts to creep but still will not pull on trailer. It has electric solenoids.
Shifts to creep. I assume you mean when selecting with creep switch. All the creep does is reduce voltage output of controller, like backing off of the contoller handle, it doesn't make any changes to hyd components. What does it do when you when you select hi/low wheel speed switch?
Does not seem to change anything! Switch tested ok, Continuity to relay is ok, I am not sure about the diodes in the blue wires going to the relays. And I do not know which valve to check.
there is a switch where the boom rests when it is all the way down, looks like a big push button, it is dead center, check this switch. this switch controls the high idle, when you switch to the platform control somehow
Are you talking about the Tilt indicator? I checked it and the boom limit switch.
The slope sensor nor the horizontal switch will affect the power of the drive system. They slow it down but will not make it low on power. Check to make sure your hi/ low speed switch is working it could be stuck in high. If it is then we can go from there. Could be blown orings on flow divider. Rotate coupler orings allowing bled over. Could be a blown drive motor. You said in your original post that the engine lugs down. I would bet it is stuck in high wheel speed or a blown drive motor. Should not be blown orings or rotate coupler those would not allow the engine to lug down. JJ
Hi/Low switch works, Relay clicks and feeds power to terminal 87 on 2 speed relay.
NO its the switch that the boom rests on when it is all the way down, on mine anyway (JLG 40H) the switch is in the middle between the two side towards the front, my machine wouldn't even drive at one point, till I un-stuck this switch. if your looking at the machine from the platform the section where the boom goes between, look there.
This machine has no switch that the boom rests on. I have tried to attach pics.
I think your in hi drive. Let's keep this simple for now, we can check components later. If you don't know which solenoid valve controls the high drive, then simply locate the high drive hoses going to motors. Each drive motor will have 2 large hoses connected to them. That's the drive hoses. Then there will be a very small hose that goes to the brake. There will be one hose smaller than drive and larger than brake hoses. It should be on the end plate of the motor, in between the drive hose fittings. Disconnect that hose, use plugs and caps to block hose and motor fittings. Or you could do this underneath the center of the machine where the high drive hoses tee off to go to motors. Once you block these lines, you should try your machine and see if it is in low drive. If it is, then we can move on to cause.
I will not get a chance to do this till Monday. I will post the results then. I really want to THANK everyone who is trying to help me. It is greatly appreciated.
Traced high lines back to valve , disconnected and plugged. Machine pulled and loaded fine ( Hurray ). I reconnected the lines and machine seems to be working OK. What could have been the cause and what should I check or repair?
So, now when you work the toggle switch at platform, does it go in and out of high drive?
Yes. Everything seems to work fine. I did notice when it was stuck in high it was very fast. Now it is back to a normal high or low wheel speed. Again, I want to thank everyone who has replied to help me. ATCOEQUIP, I especially want to thank you for putting me on the right path to the high drive.
Just happy to hear ya got it working proper. Do you mean; when it was struck in high drive it was "faster" than normal high drive? Hmmm, that's a quirk I haven't seen before. The high drive is actually quite simple. The machine has variable displacement axil piston motors. In low drive, the piston swash plate is in a postition that holds a certain low speed of the motors. When you select high drive, it sends voltage to a solenoind valve that applies fluid pressure to the high drive control hoses going to motors. This pressure goes to a piston in the motor that changes the position of the swash plate which increases speed of motors but reduces torque (pulling power), which is why you had a hard time loading it. If it was "faster than normal" when stuck, not sure what caused that.
Hello, New to the forum, I have a problem with my 2000 40H. I have used the info on this forum numerous times to diagnose problems in the past, what a well rounded crew you guys are! Anyways, my 40h has been running fine for the most part for the time I have had it, last week we were using it for the entire day with no problems. After sitting for 2 days alone, its developed a mild cough (poor idle, weak hydraulics, ect) After tinkering with it for a few hrs on site I called a 100$ per hr service guy, he told me my carb is dirty... duel fuel lrg 423. I asked him specificially to run diagnostics on the governor and the ignition system ( im not buying the carb story, going to clean it regardless, if its even a carb?) The mechanic hasnt got back to me, but after speaking to precision governor on the phone I am convinced its the governor. The machine Idles poorly, but when you manually pull the linkage on the carb/throttle body it revs up and idles, however it will not sustain the idle when the hydraulics are actuated (immediate bog and shut down). Thanks guys, Eric
Welcome to HEF epd. To say "it idles poorly" can be misleading to those who don't know JLG machines. Especially if you don't clarify as in idles rough poorly, or runs fine but won't idle at all poorly. The reason I say this is because when a Precision Governor is used, the idle stop screw is backed off on the carb, the Precision Governor controls governor the idle speed of the carb. If the PG malfunctions the engine will simply die because the throttle stop backed off. I'm near certain that you can send your Precision Governor to Hindley Electronics and they can test it for you. > https://www.hindleyelectronics.com/
Thank you for the reply Willie. Sorry, to be more clear, the machine idles like an old hot rod with a wild cam, just barely running but still turning over. When any function is engaged the hydraulics operate painfully slow, further slowing the idle and killing the engine. I can manually hold the throttle cable (rod) to rev the engine and hold a high idle, however the hydraulics still slow the idle and kill the engine while manually controlling the idle. I will certainly look into sending out the gov. Eric
It sounds like the Gain has gone haywire in the PG, it's one of the adjustable trim pots on the circuit board of the PG. Gain set too low, governor is sluggish to respond. Gain set too high, engine speed surges up and down, up and down continually. You could try adjusting the Gain pot, but it sounds like you might need to have the PG unit tested.
I read somewhere about adjusting the PG, I dont believe mine is adjustable (inside is factory filled with epoxy) Suppose Ill check availibility tomorrow and possibly order one. I consider this machine the backbone of my crew and with the mucky spring weather we need it back asap, the scissor lifts just dont cut it Thanks again Willie, Ill update when I know something! Eric
Cleaned the carb today. After I started it up it ran like a top, until I hit the hydraulics, the engine goes limp and dies. Could it be the little solenoid on the backside of the carb? Also the governor seems to be actuating the gas properly.
If the PG is attempting to throttle engine when the engine gets a load, yet it stalls out, likely is carb problem. And in my experience, not sure what you have in Canada, but here in the states they blend ethanol in the gas. That stuff is horrible for carbs, especially small ones. I've had more problems with carbs, Zenith in particular, since we started using alcohol gas. It's best to take the carb apart and clean in a good carb dip solvent. I've had folks say running Sea Foam through the carb helps, haven't had a chance to try it myself. One other option you have is to use propane instead of gas. I have found they work far better on propane, eliminates the gas/carb problem.