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978-368-3325
Compactors & Balers · Hydraulic · H-1

The Motor Runs But the Ram Won't Move at All

A motor that runs normally with no pressure on the gauge means the pump is not moving oil, or the oil it moves is going straight back to tank. Sheared coupling, failed pump, oil below the suction inlet, a suction valve left closed after service, a relief stuck open, or a directional valve not shifting. Two of those you can check yourself in five minutes.
Get a Technician Out — 978-368-3325
All Hydraulic Symptoms
Tier 1 to check oil and valve position. Tier 3 for everything past that.
Step One

Four Things to Check Before You Call

All four are Tier 1, all four are from outside the machine, and two of them solve this call often enough to be worth the five minutes.

Read the sight glass.

Oil below the suction inlet means the pump is pulling air. This is the first thing a technician looks at and the most common thing nobody checked.

Find the suction ball valve and look at the handle.

A suction valve closed after service is a classic. The machine ran fine before the work and does nothing after it.

Listen to the pump.

A pump moving oil sounds loaded. A pump moving nothing sounds free and light. A pump screaming is cavitating and should be shut down now.

Watch the gauge through a full cycle attempt.

Zero the whole time is different from a needle that twitches and falls back. Note which.

Note whether anything else on the machine changed.

New noise, new leak, recent service, recent electrical work. All of it narrows the list.

If the pump is screaming, stop

A cavitating pump destroys itself in hours, not weeks. If the noise is a scream or a knock rather than a normal working sound, shut the machine down and leave it down until someone looks at it. Running it to “see if it clears” is how a strainer service becomes a pump replacement.
The Shortcut

Did Anything Happen Right Before This?

This fault very often has a cause with a date on it. Two questions answer a surprising share of these calls.

Was the machine serviced recently?

A suction valve closed and never reopened, a filter change that introduced air, a hose reconnected to the wrong port. If the machine worked before the visit and not after, start there.

Was there electrical work upstream?

Reversed phase rotation after a panel change, a new starter, or utility work makes the motor turn backwards. It sounds completely normal and pumps nothing. This is an electrical fault wearing a hydraulic costume.

Neither?

Then it is more likely wear or a mechanical failure — coupling, pump, relief or valve — and it is a service call rather than a five-minute fix.
Narrowing It

Six Causes, Easiest First

  • Oil below the suction inlet — The cheapest possible answer. Top it off, then find out where it went — the oil is on the ground somewhere.
  • Suction valve closed — Free to fix, and the reason to check it before anything else on a machine that was recently serviced.
  • Reversed rotation — The motor is turning backwards. Confirmed with a rotation tester, corrected by swapping two legs at the starter. Electrical work, not hydraulic.
  • Sheared pump coupling or spider — The motor spins and the pump does not. The elastomeric spider between them is a wear part and it is designed to be the thing that fails.
  • Relief stuck open — Everything the pump makes goes straight back to tank. Cartridge replacement, or sometimes contamination holding it off its seat.
  • Failed pump or unshifting directional valve — The expensive end of the list, and where this lands when the cheap answers are ruled out.
Why It Matters Now

Don't Keep Cycling It

The temptation with a dead machine is to keep hitting start. Three reasons not to.

A starved pump is being destroyed

If the cause is low oil or a closed suction valve, every second of running is damage to a component that was fine this morning.

Repeated starts cook the motor

Especially if the fault is partly electrical. Each restart against a locked or single-phased condition heats the windings further.

The evidence disappears

Oil level, the position of a valve handle, the sound it makes on the first start — those tell a technician more than the machine will after twenty attempts.
Before You Call

What We Need to Quote It

You do not need all of this — the make and model plus photos is usually enough to get started. But the more of it you have, the closer the first number is to the final one.
  • Bore — Inside diameter of the barrel. Stamped on many data plates; otherwise we measure it.
  • Stroke — Fully extended length minus fully retracted length.
  • Rod diameter — Across the chrome, measured with calipers if you have them.
  • Mount type — Clevis, cross-tube, trunnion or flange — and the pin diameter.
  • Pin-to-pin retracted — Center of one mounting pin to center of the other, ram fully in.
  • Ports — Size, thread type, and whether they face the same direction or opposite.
  • Machine make and model — Off the data plate. It often tells us the cylinder before you measure anything.
  • Photos — The whole cylinder in place, both mounting ends, and a close shot of the rod.

If you can't get the measurements

Don’t climb on the machine to get them. Send the make, the model and the photos, and we will take the dimensions when the cylinder is out — or bring a replacement with us if we already know that machine.
Safety

Where Your Checking Stops

Tier 1 · Site check

Reading the sight glass, looking at a valve handle, listening, watching the gauge. Nothing opens.

Tier 3 · Service technician

Anything inside the cabinet, any work on the pump, relief or valve, and any rotation testing on a live 480V three-phase supply.

Do not crack a fitting to check for pressure

Stored hydraulic energy is the hazard that makes this Tier 3 no matter how simple the repair looks. Loosening a fitting “to see if there’s still pressure in it” is how people get injection injuries — which do not look serious for the first hour and are a surgical emergency. Pressure gets relieved deliberately and confirmed at the gauge.
Applies To

Compactors and Balers Both

This fault lives in the power unit, so it behaves the same on a stationary compactor and on a vertical baler. One difference is worth naming.

On a baler

Identical fault. The one baler-specific check is the chamber door interlock — a vertical baler with the door not fully latched will run the motor and do nothing, which looks exactly like a pressure fault from across the room.
Questions We Get

No Pressure, Answered

The gauge reads zero. Could the gauge just be broken?
It can be, and a dead gauge on a working machine is common enough to be worth ruling out — but the ram not moving is independent evidence. If the gauge reads zero and the ram works normally, suspect the gauge. If both are dead, believe the gauge.
The machine is running, which is not the same as fixed. That oil went somewhere. Until you know where, you have an active leak and a machine that will do this again — usually at a worse moment.
That is exactly what it looks like. The motor runs at full speed and sounds healthy because it is spinning against almost no load. The pump sits still. From ten feet away the machine looks fine and simply refuses to do anything.
Onsite response across New England, 24 hours a day. Call with the make and model, what the gauge reads, what the oil level looks like and whether anything was serviced recently — that usually decides what goes on the truck before we leave.
Get It Running

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T&T Weber Hydraulic Inc.
184 Stone St, Unit 5
Clinton, MA 01510

Where we go

Onsite compactor and baler service throughout New England — Massachusetts, Connecticut, Rhode Island, New Hampshire, Vermont and Maine. Cylinder reseal and replacement, domestic replacement cylinders, hydraulic, electrical and controls, and full mechanical repair.