Lift gate troubles. Please help.

[obijuank5]

Tldr. Cant get the lever switch to actually make it run. I can jump it and run the pump but then the cylinder wont extend. I need some guidance.

Got my bed going and getting the lift gate working. I knew it needed something. I have replaced the electric motor and a new solenoid. I put a new input shaft seal and bearing in the pump.
I dont know the correct wiring but this is what I know.
I can jump the solenoid and make it run.
There is only one hose here. Outlet of the pump to the base of the ram.
I have disconnected the hose from the base of the ram and confirmed fluid is circulating. It is a solid stream and seems to have decent pressure. The ram extending raises the lift gate cables. Lower the gate with a fluid bypass switch.

I am by no means knowledgeable about how to wire a solenoid. I read something by billavista and made sense of a little bit.
I thought I had a handle on the hydraulic side but im having trouble there too.

Large cable is straight from the positive terminal. Little black is from the negative terminal. Green wire is the one that comes from the contact of the switch to the s terminal. Isnt there supposed to be some wire telling the switch to be a switch?
One pic is the switch open, then me pushing on the switch to run the motor.

Im grateful for any help. Thanks!

 

[Fordum]

I have worked on and used many tailgates. The single hose ones are dead simple. I'll have to study the pics more to see what is your actual problem, but here is what you need to know.
The reason the tailgate won't work when you jump the solenoid, is because that lever switch is not just a switch. I also works the valve to send fluid to the cylinder.
If its the same as all the ones I have used, you pull down on the lever to raise the tailgate, push up to let it down.
Try this:
Pull down on the lever and hold it. Then jump the solenoid. With the lever down, the fluid from the pump will go to the cylinders and the tailgate should rise.
You either have a bad switch under the lever, or the solenoid is wired wrong.
Let me study the pics and I'll see if I can't pin it down.

 

[Fordum]

I think I see it, but I'm not sure.
When you push the loop/switch with your finger, did you say the motor ran then? If so it should run when the rod pushes it.
If it does not run either time, then I think I've got it.
The solenoid needs power and ground to fire and run the pump, if those two small terminals are both ends of the coil.
However, there are different types of solenoids. If that is the original solenoid, then we should be all right. If not, then we need to do more testing.
I suspect you don't have an ohmmeter, so lets do a quick, dirty, and only slightly dangerous test......
Take the green wire off the solenoid terminal.
Hook a wire about that size to the battery terminal, and quickly brush it across the terminal the green wire was hooked to.
If you have the right type of solenoid, it will come on briefly and the motor will start to run.
The worry is that if its a different type that terminal might be internally hooked to ground, so don't let that wire stay on it long.

If the solenoid fires and runs the motor, then we should be home free.
Take a good look at that switch with the green wire hooked to it. I think you will see that when you move it to the run position, it grounds that green wire to the frame.
Which means that you need to hook a hot (positive) lead to the other terminal where the black wire is now. Then, that terminal is hot, and when you ground the other one with the switch and green wire, the solenoid fires and turns on the motor.

I know I posted a lot to say something simple, but I try to cover all the bases and answer all your questions beforehand. That's not entirely possible, but I usually get a few of them.
Post back if you have more questions or are not sure of this answer.

 

[obijuank5]

Thank you for the insight. Ill get on it this afternoon and see what results I get.

 

[Fordum]

Hope it works. There are two ways to do that solenoid correctly. With two isolated terminals each hooked to one end of the coil, or the ones like used on old 8N Ford tractors. One end of the internal coil is hooked to one of the two main terminals. That terminal has to be hooked to the battery.
Then, the other end of the internal coil is hooked to the single top post.
When you ground that one, the solenoid fires.
The "common" solenoid that we used on most all our cars, has one end of the internal coil hooked to the mount which gets grounded when you bolt it on.
Then you put battery voltage to the single terminal and it fires.
But that means you have to have isolated switch contacts and have a hot wire run to one side. Its easier to just run one wire to the switch and use the switch housing for the other terminal.
Some of the other two control terminal solenoids use the ground for one side and you hook the hot wire to the one terminal to fire it.
The second small terminal is hooked to the output side of one of the big lugs. When the solenoid fires, that terminal gets hooked to the battery.
The older coil and points type ignition had a spark coil that was to designed to run on less than battery voltage. That was so that it developed full power when the starter was dragging the battery voltage down.
To keep it from burning up when running, they put a ballast resistor in the circuit to reduce the voltage to the coil down to what it was designed to run on.
When you were cranking, that extra terminal on the solenoid would bypass the resistor and put full battery voltage to the coil.
So, you see why I did not feel safe just telling you to run the hot wire to where the black wire was hooked if that was not the original solenoid.
Someone could have put in a completely different type one.

 

[obijuank5]

So just for fun I put in the solenoid that came with it. I hooked the red jumper wire up as pictured and it does run the motor with the switch now. I have run the black ground wire to the case. I also confirmed that the pressure release switch to let the gate down is adjusted to be closed all the way when the electric switch is in its neutral position.
So thats squared away! Thank you!
Secondly, this ram still isnt budging.

 

[obijuank5]

So now im sure that I have fluid bypassing somewhere for some reason. I can stop the flow at the end of the hose with my thumb.
Or the bomba no bomba no more.

Broke a fitting trying to loosen it.
Gonna visit the hydraulic hose place that I got my seals from and see if they can help.

 

[Fordum]

We are missing something. I think I know what it is, but not sure where.
First, what is that last picture? Is that the release valve that the handle pushes when its moved?
Second, let me tell how a lot of these units work, and you see if you can see where the problem is.

I had one that just had a push button and a knob type valve. You tightened the valve closed, and pressed the button to raise it. All the button did was turn on the solenoid to run the pump. The pump was hooked to the ram all the time.
You opened the knob valve to let it down.
Those are fairly obvious, and I don't think yours is that way.

The others have a lever or something that you push up and down or back and forth.
When the lever is is sitting at rest, a hydraulic valve attached to it is in the closed position. Any fluid in the line going to or from the cylinder is blocked, and usually the pump is not hooked to that line. So the lift stays wherever it is.
When you move the lever to the go down position, it either moves that valve to release the fluid back to the tank, or hooks up the pump with no power so the fluid flows back through the pump.
Depends on what type pump it is. Some will let the fluid flow back, some won't. Either way, it releases the pressure on the line and cylinder.

Here is the important part: When you move the lever to the raise position, it not only turns on the pump, but it moves a valve that connects the pump to the hose and thus to the cylinder.
That valve might not be obvious. Trace the hose from the cylinder to the pump. There has to be a valve of some kind in there even if its just a release valve.

STOP: Just read your last post, pretty much ignore what I wrote before.
Again trace that hose. Look very hard at the valve you find.
Looking at that last picture, if that is the valve, and you press it down to release the pressure, can the setup be adjusted so that it can raise up higher?
I'm thinking that it may need to come up to get out of neutral. Or go down if you press down to raise the gate.
If not that, look hard at the pump.
See if there is a nut, or screw or something on the side, top or bottom that just does not seem to do anything.
A real common one is a big acorn nut. If you see that, take it off and see if there is a big screw slot under it. If so, that is the bypass pressure valve.
Screw it in to increase the pump pressure.
Pretty much all those small electric pumps have a pressure bypass valve somewhere on them.

To make a long story short...( TOO LATE) either the control valve is adjusted wrong, the bypass pressure valve has backed its self off, or the pump is bad.
I would suspect the pump last.
Got a brand name and model? I may be able to find some info on it.

 

[Fordum]

The more I look at that last picture, the more I am convinced it is the source of the problems. Just guessing, but does that double flat shaft push down when you tell it to raise or lower, and pops up farther the other way?
If so, that is the control valve, and it may still be out of adjustment.
Plus, the big nut its coming out of may well be the pressure adjustment. If it will screw up and down in the pump, it may just need tightening to increase the pressure.

 

[obijuank5]

Dont sweat it. You have been more than helpful! That is the pressure relief valve and when you push that down it is what lowers the gate by the ram collapsing. I did adjust it to where the little button was raised fully amd barely not touching the lever that depresses it. It got a full stroke that way. I did take the valve out to make sure it was clean and actually moving. Passed visual inspection.
At that point I broke the fitting. This will have to wait until next week when I can actually get the hose replaced.
I believe it to be a monarch 3300. It is an eagle lift 38 series.


That big nut is the body of the valve itself. That is not an adjustment.

 

[diesel4me]

I'd refrain from using your finger as a pressure tester too..
Hydraulics can force the fluid under your skin and inject a fatal dose pretty fast..
It's like your not supposed to put an air gun up your rectum and pull the trigger either...its not a joke....kid in school had his colon damaged during a "freshman prank" and could have died!..

 

[obijuank5]

Well thats one hell of a story there bob. Yikes!
You are definitely right. I know what hydraulics are capable of and after a few incremental tests that showed me it was nutless for pressure I decided to try it.

 

[Wes Harden]

Yes use card board if you must. Is this a Tommy gate? Could you post a pic of the switch?
Sorry if I missed it just skimmed through, bed time.