JLG60H Engine stops when Foot Switch is pressed

[01RAMer]

I have a JLG 60H with an LSG-423 engine (Zenith Mdl 33 Carb with electric choke) with an E301C Rev.1 Precision Governor Controller. Engine run well and ground functions work without issue.
My problem is when I switch over to platform. For a long time now, I'd step on the foot switch and the engine would die. If I would keep tapping the switch eventually I could get the engine to ramp up.
When the engine is cold, it sometimes works normal but starts to act up more and more after several minutes.
Thinking it was with the PGC, I completely disconnected the controller and set the throttle manually. Upon stepping on the foot switch I would hear the engine labor ever so slightly and all functions worked. To my surprise when everything started to warm up and I would depress the foot switch, the engine would want to die. Even tapping the switch killed the engine. I'm hoping its a relay but I have no idea which one. I also thought it might be a hyd valve sticking but the relief valve should keep the engine from dying. I'm having a terrible time with the schematics and am at my wits end.
Please, I would appreciate any help that anyone could give me in this matter. I am totally dumb founded!

 

[BillG]

When on ground control if you twist the throttle open manually does the engine stutter or does it rev up normally? Also are you running on gasoline only or LP gas, if gasoline, how old is it.

 

[01RAMer]

When on ground control if you twist the throttle open manually does the engine stutter or does it rev up normally? Also are you running on gasoline only or LP gas, if gasoline, how old is it.

The engine runs well with no hesitations. The engine revs up normally when manually accelerating. This is only running on gasoline. I believe it is a 1985 vintage.

 

[01RAMer]

In reading other threads for JLG, I see there is a tremendous amount of very intelligent people out there helping others with their issues. Won't anyone help me... Please?

 

[BillG]

i don't have a schematic for this one. If the engine is failing to run when you hit the deadman switch then we need to find out if we are loosing ignition or fuel.

 

[01RAMer]

i don't have a schematic for this one. If the engine is failing to run when you hit the deadman switch then we need to find out if we are loosing ignition or fuel.

I was playing around with it today and fuel is definitely not shutting off, and the engine was replaced about six or seven years ago and runs great on ground. It shuts off as soon as I het the switch and as soon as I let it up the engine takes off again. Now I will say that on occasion by rapidly stomping on the switch, at times the engine will catch and operate perfectly while the switch is depressed, but as soon as I release the switch, everything starts again with the engine being killed when switch is depressed. I checked the switch and there is no problems with it. Works first time every time. Each micro switches inside work perfectly when tested. I tested the switch again while having one of these episodes.

When I was a kid, I would take my dad's car for a ride (I was 16 and it was a stick) and shut the ignition off momentarily and turn it back while running down the road, which caused a loud backfire from the buildup of fuel in the cylinder being ignited. After I blew out the muffler my dad dealt with me and that ended that. The reason I'm telling you this is because, as I was tapping the switch to coax it to run, it all of a sudden let out one heck of a loud backfire out the muffler. This tells me that the ignition is actually being shutoff when I press the switch, yet some times I can coax it to catch and run. What circuit in the foot switch could be connected to the ignition? It makes no sense to me which is why I came to you, the experts.

Reading the other threads, the circuits on a 40H sound very similar to the 60H.

 

[BillG]

Do you have a pdf of the schematic? It's been 10 years since I worked on one and don't remember much as far as the controls are concerned.

 

[OFF]

Hi, I missed this thread somehow. We had 2 60H's with Ford LSG's engines, so I have some info and experience on them.

First of all, when you step on the foot pedal, the engine should go from a low idle of 900 RPM to 1800 RPM. The only time the engine goes to high (3000 RPM) is when the drive controller is fully "stroked".
If the engine doesn't make that first increase to 1800 rpm, the load of the hydraulic system will kill the engine. Can you watch what's happening (through the top hatch) while someone steps on the deadman pedal?
If the governor is not even attempting to speed the engine up, I would say you have a governor problem. Possibly, the governor has lost it's power supply. That's step 1. One terminal on the governor control box needs to have battery voltage to it.

I have manuals and schematics.

 

[01RAMer]

Do you have a pdf of the schematic? It's been 10 years since I worked on one and don't remember much as far as the controls are concerned.

I have the manuals that contain the schematics but they aren't easy to read. I'll try to find some online if I fail at scanning them in, there are 18 pages. I don't know what size attachments this site will allow as this may also be an issue. Do you have any idea?

 

[01RAMer]

Hi, I missed this thread somehow. We had 2 60H's with Ford LSG's engines, so I have some info and experience on them.

First of all, when you step on the foot pedal, the engine should go from a low idle of 900 RPM to 1800 RPM. The only time the engine goes to high (3000 RPM) is when the drive controller is fully "stroked".
If the engine doesn't make that first increase to 1800 rpm, the load of the hydraulic system will kill the engine. Can you watch what's happening (through the top hatch) while someone steps on the deadman pedal?
If the governor is not even attempting to speed the engine up, I would say you have a governor problem. Possibly, the governor has lost it's power supply. That's step 1. One terminal on the governor control box needs to have battery voltage to it.

I have manuals and schematics.

Off, thanks for your input, I appreciate it. You must have missed my lead in thread, and in it I had said that I had thought this problem was due to a faulty PGC, so I completely disconnected (eliminated) the PGC an am currently running the throttle manually. I'm still having the problem so it's not with the PGC.

 

[OFF]

I've got a set of the factory schematics on big 11 x 17 paper at work, I'll check them tomorrow and see if I can reason out something in the foot switch that would be cutting out the ignition.

 

[OFF]

I didn't see anything in the basket foot switch wiring that would explain what's been happening to your machine, however I ran across a print that's very interesting called "Engine Shut Down". It looks like it was an add-on after the machines were built. It references something called "Engine Stop Valve". The only thing I remember on your engine that even comes close to being an engine stop valve is the fuel shut-off solenoid located just under the fuel bowl of the carburetor. You can try running a jumper wire from this solenoid to battery power and see if it has any effect on your stalling problem. You might want to disconnect the wire running to this solenoid first, just in case it could back-feed somewhere and let the smoke out of something you don't want to let the smoke out of.
Let me know what happens.

 

[01RAMer]

Fuel Shut-off Solenoid

I didn't see anything in the basket foot switch wiring that would explain what's been happening to your machine, however I ran across a print that's very interesting called "Engine Shut Down". It looks like it was an add-on after the machines were built. It references something called "Engine Stop Valve". The only thing I remember on your engine that even comes close to being an engine stop valve is the fuel shut-off solenoid located just under the fuel bowl of the carburetor. You can try running a jumper wire from this solenoid to battery power and see if it has any effect on your stalling problem. You might want to disconnect the wire running to this solenoid first, just in case it could back-feed somewhere and let the smoke out of something you don't want to let the smoke out of.
Let me know what happens.

OFF, you are correct, I do have the optional Fuel Shut-off Solenoid on my carb. I just rebuilt the carb while I've been troubleshooting and it is working just fine but I haven't traced the wire going to it to power it. I will try jumping it to see if it makes a different. You may be on to something.

On one of the schematics (I have a very hard time reading these), Drawing Number 5-1282353, there is an "Over Speed Lockout Relay" (lower right corner) that looks like it's powered by the Oil Pressure Switch, and I think one of the wires from the relay goes to the DIC (Distributorless Ignition Coil). I was thinking this might be a possibility, but I don't know where to find the relay on the machine, and I'm having a hard time reading the schematic wiring for it. If this relay is faulty and grounding out the coil, it could also might be my problem and shutting the engine down. You wouldn't know how to identify where this relay is, would you? If it's in the manual I haven't found it yet.

 

[OFF]

something else you can check out. Put a volt meter onto the ignition circuit in the basket - any yellow wire - and see what the voltage is when you step on the foot pedal. If it drops below 10 volts, that's what is causing your problem. Then you can start checking to see where the big voltage drop is. IIRC those engines shut down at 9.6 volts.

 

[01RAMer]

In between the raindrops, I did some checking. First, the Fuel Shout-off Valve on the carb is not loosing power. I then checked the voltage at the platform and when the foot switch is depressed, the voltage drops to zero. I then eliminated all the circuits in the platform panel that were fed but the foot switch. I got to the point where the only thing I had on the foot switch was power in to the switch, and a wire coming out that goes somewhere back to the main panel, and with this setup, again when the foot switch was pressed, the engine died as long as I held down the switch. I didn't get any further due to being rained out.

The funny thing about all this is that when I first start the lift, everything works fine for the first minute or two, then it all falls apart. I know I have to go to the main panel next but where? Any thoughts?

 

[OFF]

How does your wiring in the boom ladder look? And bad spots where wires could be shorting out?

 

[01RAMer]

How does your wiring in the boom ladder look? And bad spots where wires could be shorting out?

I can't really tell. I'll have to isolate wires at the main terminal box and check them. I'll start with the one coming back from the platform. This will take a while. When this rain stops I will have my work cut out for me.

On the schematics there are numbers in square boxes which are connectors to another box with the same number. Do you know what the numbers in circles pointing to wires and other items represent? I haven't be able to figure them out. Also there are numbers next to some wire colors and not to others which other wires with the same colors have a different number with no apparent matches any where else on the schematic. Do you know what they represent? Thanks for al the help you have given me so far!

 

[OFF]

Ramer, on the terminal strip in your basket, is there a diode running from terminal #4 to terminal #7? If that diode is defective, it could supply a path from ignition power direct to ground. It's worth checking.

 

[01RAMer]

Diode

Ramer, on the terminal strip in your basket, is there a diode running from terminal #4 to terminal #7? If that diode is defective, it could supply a path from ignition power direct to ground. It's worth checking.

The people who had this machine before me had removed the terminal block, so I don't have the terminal numbers to go by. I know there is a diode in the foot switch between the White wire and the Orange wire bridging the Normally Open and Normally Closed lugs on one of the micro switches. The Common Lug on the switch has a black wire.

Strange thing, the white wire from the foot switch goes to terminal 85 of a relay which is mounted to the side of the panel, to energize the relay, and no drawings show it. A wire from 86 goes to ground. The energized relay gets power from the hot side of the horn button to terminal 87 and sends pwr to the P-Q Controls via terminal 30. I've checked a newer 2012 schematic for the 60H, which doesn't appear to be much different, and it also doesn't show this relay. This unit was upgraded to the E301 PGC, but even in the upgrade installation material I got with the lift, it doesn't show this relay. I wonder if they used that relay to circumvent the diode. Can you tell me where the diode connects to?

I took a look for the diode and didn't see one in the platform panel.

 

[OFF]

Do you see a capacitor in there anywhere? It's a funny symbol on the drawing I have. Could be either a capacitor or a diode. Capacitor would be a value like 1000uf @ 40 volts.

We don't own a 60H anymore, and it's been many years since we did so I'm working from memory. The 60H schematics are really crappy. Not crappy is in a bad copy, crappy as in poorly drawn and poorly explained. Everything is based on the color of the wire rather than on numbers on a terminal strip. The stuff I have is dated between 1984 & 1986. Both the parts books and schematics show a double terminal strip in the basket, it sounds like your machine may have been modified. If that relay you mentioned has malfunctioned and now has a direct short from 85 to 86, that would certainly cause the voltage drop you are looking for & kill your engine.

My drawing shows a diode on the foot switch, on one set of contacts between NO & NC contacts, orange wire & white wire. It shows the black wire going to NC on the other contact set, and a green on the common. Orange & white wires switch your basket power, black & green wires are the starter button - to prevent you from engaging the starter with your foot on the pedal.