Cat 247b Stalls under load

[2006247b]

My CAT 2006 247b stalls under load. It runs fine on idle and will drive slowly but when it accelerates it stalls or if i use hydraulics it stalls. Checked and replaced fuel pump, changed filters air and fuel,checked hydraulic fluid levels.

Any Ideas?

 

[brdgbldr]

My CAT 2006 247b stalls under load. It runs fine on idle and will drive slowly but when it accelerates it stalls or if i use hydraulics it stalls. Checked and replaced fuel pump, changed filters air and fuel,checked hydraulic fluid levels.

Any Ideas?

I’m not familiar with that machine, but it could be the governor.

 

[2006247b]

So how does the governor affect this and how might I correct it? Thx.

 

[brdgbldr]

So how does the governor affect this and how might I correct it? ThxThere are different types of governors. Some are part of the engine otheres are belt driven.

There are different types of governors. Some are part of the engine and others are belt driven.

The governor works by opening up the throttle when the engine is under load. If it is not working then the engine will run fine when not under load but as soon as you put a load on it, it will bog down.

Like I said I am not familiar with that machine. Your governor could be bad or out of adjustment.

Maybe someone on here that is familiar with the machine will chime in.

 

[David-Q]

Hi there — good work already replacing the filters and fuel pump.
Your symptom (“runs fine at idle, stalls when accelerating or using hydraulics”) points to one of three main systems: fuel delivery under load, air intake restriction, or engine load control (hydraulic system overloading or governor not compensating).

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1. Fuel supply restriction under load
   • Even with a new pump and filters, the pickup tube inside the fuel tank may be cracked or partially blocked — it will supply enough fuel for idle, but suck air when higher flow is needed.
   • A collapsed or kinked fuel line between the tank and the injection pump will cause the same symptom.
2. Air in fuel line or weak injector pump
   • Small air leaks at the filter base or fittings can cause the injection pump to starve when pressure demand rises.
   • If you can install a clear hose in the return line and see bubbles when revving — that’s the cause.
3. Hydraulic pump loading the engine excessively
   • If a main relief valve is stuck partially closed or the pump compensator fails, the engine can be overloaded whenever hydraulics engage.
   • You’ll hear the engine lug immediately when trying to lift or drive faster.
4. Air intake restriction
   • Check for a collapsed intake hose, blocked pre-cleaner, or stuck air restriction indicator.
5. Fuel injection timing or worn injectors
   • After ruling out the supply side, weak injectors or mistimed injection can cause loss of power under load, especially if the engine smokes dark or white just before stalling.

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Step 1: Check for vacuum in fuel line (fuel restriction test)

• Install a vacuum gauge before the injection pump.
• If vacuum > 5 inHg when engine starts to stall → restriction between tank and pump.
• Solution: clean or replace the pickup tube, fuel line, or shutoff valve.

Step 2: Bleed the fuel system completely

• Loosen injector line nuts and crank until fuel spurts solidly (no bubbles).
• Retighten and restart — if problem improves temporarily, air leak is confirmed.

Step 3: Bypass hydraulic pump (to isolate engine)

• Loosen or disconnect the drive to the main hydraulic pump (only if safe and possible).
• If engine now revs freely → problem is hydraulic overload or stuck relief.
• Check and clean main relief valve, confirm system pressure doesn’t exceed spec (~3300–3500 psi typically for Cat 247B).

Step 4: Check air intake system

• Inspect hoses, filter housing, and pre-cleaner. Replace if collapsed or blocked.

Step 5: Fuel pressure test (electric lift pump output)

• Pressure at the injector pump inlet should be 4–6 psi steady.
• If it drops under load, check wiring to the pump or replace with verified OEM unit.

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• On older Cat 247B, the fuel return line check valve can stick closed, causing pressure buildup and stalling — remove and clean it.
• The hydraulic charge filter (not just the main filter) can clog and make the pump pull high torque from the engine; replace if in doubt.
• If you suspect hydraulic overload, a Fairy Deer precision gear pump can be a reliable replacement or test pump — its stable flow and lower parasitic losses make it a good diagnostic substitute to isolate engine vs. hydraulic load issues.

Wanna help? please contact fairydeerhydraulic expert support.