JLG 40H problems and fixes

[mark3885]

When I hit the emergency stop on the platform control panel, the motor dies but then will rev up . It never dies it will keep doing this. Is the emerg . stop circuit supposed to ground the coil or does it cut fuel. I need to correct this as it doesn't allow me to shut down the motor if I'm going to be stationary , like painting.

 

[willie59]

Welcome to the forum mark3885. :usa

Gasoline engine 40H?

 

[mark3885]

yes , LSG 423

 

[willie59]

yes , LSG 423

Yep, what I thought. The reason your engine doesn't shut down is because of a problem with the anti dieseling solenoid on the carburetor. The anti diesel solenoid stops fuel flowing through main jet of carb and kills engine. When you hit E stop button, it takes away power from choke heater and anti diesel solenoid. The E stop kills power to ignition coil pack as well, but it will continue to run from voltage input from alternator on ignition circuit. The anti diesel solenoid has to work proper to kill the engine or it will continue run when E stop is pushed in. You can remove the solenoid from the carb and test its operation using jumper leads to a battery. It may be stuck from varnish build up. Use some carb cleaner on plunger pin as you work it in and out of solenoid body if it's stuck, then test it again with jumper leads. You need to get the plunger pin to where it will pop in and out when power is applied then taken away. And the rubber seat at the tip of the plunger pin needs to be in good shape as well.

 

[mark3885]

I just rebuilt the carb, so the inside and out are clean as a whistle. I'll have to check the solenoid. So I would assume that shutting off the master switch , will kill all power to the engine, this is the only way I can shut it down.

 

[willie59]

I just rebuilt the carb, so the inside and out are clean as a whistle. I'll have to check the solenoid. So I would assume that shutting off the master switch , will kill all power to the engine, this is the only way I can shut it down.

I'd have to look over schematics to see exactly how the master switch works. All I know is, on the Ford VSG411 and LRG423, when you hit the E stop, it takes power away from the anti diesel solenoid on the carb. The engine will run for a short moment, then die because the fuel flow through the main jet of carb is cut off. If that solenoid isn't working properly, the engine will continue to run, or, "diesel".

 

[cnckeith]

any conclusion? mine is doing the same thing.. was it the solenoid? thanks

any conclusion? mine is doing the same thing.. was it the solenoid? thanks

 

[willie59]

Welcome to the forum cnckieth. :usa

It's pretty easy to check the operation of the anti-dieseling solenoid. It's a round cartridge looking gizmo located at the base of the float bowl on the carb, has a single wire going to it. With the engine running, connect a test light or a volt meter to the wire connection terminal on the solenoid, it should have power.

Then shut of ignition, power should go off. If it doesn't, you have some form of wiring problem. If power does go off, and engine continues running, the pintle of the solenoid is likely stuck. I see it quite often with the alcohol gas we have now days.

 

[cnckeith]

thanks for the fast reply.. i'll check it tonight and report back

thanks for the fast reply.. i'll check it tonight and report back
is there a jlg 40h dedicated forum? or am i in the right place?
i've fixed my own cars all my life, but being new to the JLG, i've got a
few questions and a few mysteries to solve about the machine.

 

[willie59]

is there a jlg 40h dedicated forum? or am i in the right place?

Well, there's no particular forum thread dedicated to a 40H, no harm in posting your questions here. There's a JLG 40F thread that has grown huge and has become a single information resource for the 40F. It's your choice, you can either continue posting here, or you can start your own thread when you become a Junior Member.

 

[cnckeith]

new test data for the 40h not shutting off..

Ok.. here is what i found out....

While the engine is running there is 13.5 volts on the fuel cut off solenoid.

when the ignition on the ground controls is switched off.. the voltage drops to 12.75 (note: which perfectly matches the battery voltage while the engine is NOT running)

this is also repeated when using the platform controls, while running 13.5, and press the E stop button and it drops to 12.75.

so apparently the battery voltage is not being cut off from the solenoid when the estop on the platform or ignition on the ground control is in the OFF position. and the engine continues to run....

the only way i can turn it off is the switch from the Gasoline to LP setting on the fuel select switch.. and the volt meter shows 0 volts when this is done and the engine shuts off.. fine for ground controls.. but no way to shut off when you are in the air:-(

does anyone have a starting place for me to look for this wiring problem? does this sound like a relay related issue to you'all? and is there anywhere on line to download a 1998 40H wiring diagram? thanks in advance for any input!

 

[willie59]

I guess I should have asked, does your 40H have the Ford LRG423 four cyl dual fuel engine?

You can download operators, parts, and service manuals at JLG website, although the service manuals aren't very informative. The wiring and hyd diagrams are in both the parts and service manuals.

Go to www.jlg.com

When the home page opens, click "Services" in the left column. When that link opens a new page, click on "Parts, Operators, and Service Manuals" in the left column. That will take you to a PDF download page, simply select JLG and you machine model.

 

[cnckeith]

40h not shutting off

yes.. its a ford lrg dual fuel.

thanks for the tip on the jlg site, that's cool they still have that stuff up there.

without seeing the wiring diagram it sounds like a relay related issue since it exhibits the same problem from both the ground and platform controls, does that makes sense you'all? has anyone else seen and solved this one? thanks.

 

[willie59]

My first thought was an alternator problem keeping ignition circuit powered up, but that can't be the case if you can flip the fuel switch to the center position and engine will die. What happens when you flip that switch to center position is it turns off fuel flow to fuel pump via a solenoid valve in fuel line. Engine runs until carb runs out of fuel. Alternator ign terminal, fuel pump shut off solenoid, anti diesel solenoid, and choke are kinda on the same circuit.

I think the next thing I would try, with engine running, would be pull the yellow wire connected to terminal 86 on R18 and R19 ignition relays in lower control box. If engine dies, go back through the wiring to determine why that circuit remains powered when ignition switch is off.

If engine continues running when you pull the wire connected to 86 on R18 and R19, you either have a stuck relay or something is wired up wrong.

 

[cnckeith]

Ok.. to "solve" the problem, i cut the wire going to the solenoid and ran a new wire to the "on" side of the ignition relay. (power on when ignition switch is on). I could never figure out why the solenoid had power to it when the ignition switch is in the off position.
one hint may be the fact that the hour meter is also on and running while the ignition switch is in the off positions (and the master switch on). anyways its running and working now. thanks for this forum, and thanks to willie59 for the hints.

 

[willie59]

Ok, I need to ask a few questions. You cut the wire going to anti-dieseling solenoid on base of carb, and ran a new wire to "on" side of ignition relay. Take a look at this diagram, there should be 2 ignition relays (shown in red box), is one of these the relay you connected wire to? If so, which terminal did you connect to?







Also, if you only ran a wire to the anti-diesel solenoid, what about the carb choke, fuel pump cutoff solenoid, and 5 degree tilt sensor, these components run off the same circuit as the anti-diesel solenoid.

 

[cnckeith]

Hello.

I connected the fuel cut off solenoid to the bottom yellow (86) on R19.

I didn't disconnect the carb choke, degree sensor or anything else.. i isolated the solenoid from the circuit that those items where on since that circuit was causing the problem.
those items seem not to effect the operation of the machine if they have power to them while the ignition switch is off. i know this solution is not ideal.. really the reason why power
is on in that circuit with the ignition in the ON position should be solved to get things back to 'normal'. But isolating the fuel cut off solenoid from the problem circuit seemed like an acceptable work around with no detrimental side effects. thanks.

 

[willie59]

Well, that would kill the solenoid when you turned ignition off, at least it should. The yellow wire connected to 86 on relay 18 and 19 comes from the upper and lower ignition switches depending on the position of the upper/lower select switch. If that kills the solenoid, at least you can figure that circuit is working proper. As long as you have no detrimental side effects, I would say work it that way. If you have any other questions, ask away.

 

[cnckeith]

yeah.. it works great.. I was using the machine today.. so happy that i can now shut the engine off from the platform.

on another note.. can you tell me what the "creep" switch on the platform control panel does?

 

[willie59]

The creep switch provides very slow operation of basket functions that are controlled by PQ proportional controllers. This would include drive, boom up/dwn, swing, and telescope if telescope uses a PQ controller instead of toggle switch control.