July 2025

Bobcat 873 Fuel Pump: Diagnosis, Testing, Replacement, and Prevention Guide

If your Bobcat 873 skid steer loader is experiencing hard starting, loss of power, stalling, or won't start at all, the fuel pump is a prime suspect and requires testing before considering immediate replacement. Faulty fuel pumps are a common cause of diesel engine performance issues in these machines, but symptoms can mimic other problems like clogged filters or air intrusion. Replacing the pump unnecessarily wastes time and money. This definitive guide equips Bobcat 873 owners and operators with the knowledge to accurately diagnose a failing fuel pump, perform crucial electrical tests, understand replacement options, and execute the job safely and effectively, ultimately ensuring reliable operation and minimizing costly downtime.

Symptoms Pointing to a Failing Bobcat 873 Fuel Pump

Unlike gasoline engines with high-pressure fuel pumps in the engine bay, diesel skid steers like the Bobcat 873 use a relatively low-pressure electric lift pump. Its job is simple but critical: pull diesel fuel from the tank and push it consistently to the engine's injection pump. When this pump fails or struggles, the engine cannot get the fuel it needs, leading to clear and often progressively worsening symptoms:

Hard Starting or Extended Cranking: The most frequent early sign. The engine turns over fine (indicating a healthy battery and starter) but takes significantly longer than usual to fire up or requires multiple attempts. This happens because the pump isn't delivering enough fuel to the injection system quickly during cranking.
Loss of Power Under Load: You might notice the machine runs okay at idle or low speed but struggles or bogs down dramatically when attempting to lift a heavy load, climb a grade, or dig into material. This indicates the pump cannot supply sufficient fuel volume to meet the engine's increased demand.
Engine Stalling or Hesitation: Intermittent or sudden engine cut-outs, particularly during operation or when applying throttle, signal inconsistent fuel delivery. Hesitation during acceleration is another red flag.
Failure to Start (Cranks but No Start): The engine cranks healthily but never attempts to fire. While other causes exist (like faulty stop solenoid or major air intrusion), a completely dead fuel pump will prevent fuel from reaching the injection system.
Reduced Engine RPM or Surging: An engine that won't reach its usual operating RPMs, or fluctuates erratically while under a constant load, suggests fuel starvation. The governor tries to compensate but lacks adequate fuel flow.
Noticeable Whining Noise Change: While fuel pumps often make a faint hum or whine when operating, a significant increase in noise intensity (loud buzzing, grinding) or the complete absence of its usual priming sound when you first turn the key to "ON" (before cranking) strongly suggests pump failure.

It's Crucial: Test Before You Replace!

Ignoring these symptoms or immediately assuming the pump is bad without verification can lead you down the wrong repair path. Several other common issues share these symptoms:

Clogged Fuel Filters (Primary & Secondary): This is perhaps the MOST frequent cause of fuel starvation symptoms. Diesel fuel attracts water and particles over time. A blocked filter restricts flow dramatically. Always replace both filters first or as part of troubleshooting.
Water in Fuel: Water entering the fuel system (through condensation or contaminated fuel) can cause erratic engine performance and corrosion.
Air Intrusion in Fuel Lines: A leak (even a tiny one) on the suction side of the fuel system (between tank and lift pump, or lift pump and primary filter) allows air to enter. Air bubbles disrupt the fuel flow. Look for wetness around connections and inspect hoses.
Pinched or Kinked Fuel Lines: Check the entire fuel line route from tank to injection pump, especially after recent work or impact damage.
Restricted Fuel Tank Vent: A clogged tank vent creates a vacuum inside the tank, preventing fuel from flowing freely to the pump. Listen for a "gulp" of air when opening the fuel cap after running.
Faulty Fuel Cut-Off Solenoid: This solenoid on the injection pump stops fuel flow when the key is off. If it fails electrically or mechanically, it may prevent fuel flow altogether.
Injection Pump Failure or Injector Issues: While less common than lift pump failure on the 873, problems within the high-pressure injection system itself need expert diagnosis. Symptoms might include misfiring or excessive smoke.

Finding and Accessing the Bobcat 873 Fuel Pump

The electric lift pump on a Bobcat 873 is located near the fuel tank itself, rather than on the engine. Here's how to locate it:

Raise the Cab: Safely raise the cab/lock it in the raised position according to your operator's manual procedures. Always block the cab securely.
Locate the Fuel Tank: Standing at the rear of the machine (engine end), look down towards the machine's frame. The large metal or plastic reservoir is the main fuel tank.
Identify the Pump: The fuel pump is typically mounted on the left side of the skid steer frame rail (when looking forward from the rear) near the fuel tank. It's often situated close to the fuel filter head assembly. It's a compact cylindrical metal component with electrical wires connected to it and two fuel lines (inlet and outlet) attached.
Visual Inspection: Before testing, do a visual check. Look for obvious damage, severe rust, cracked fuel lines near the pump fittings, or significant fuel leaks around the pump body or connections. Check wiring harness integrity.

Testing the Bobcat 873 Fuel Pump: Essential Steps

Verification is key. You'll need a basic multimeter capable of measuring DC Voltage and Resistance (Ohms). Follow these steps:

Test 1: Listen for Priming (Initial Check)
* Turn the ignition key to the "ON" position (do not crank the engine).
* Listen carefully near the fuel pump location for a distinct humming or buzzing sound that lasts for 5-10 seconds. This is the pump priming the system.
* No Sound? Very strong indicator the pump isn't receiving power, its internal fuse is blown, or it's failed.
* Hear the Sound? Doesn't guarantee the pump is healthy, just that it's trying to run. Proceed to electrical testing.

Test 2: Verify Pump Power (Voltage Test)
* Locate the electrical connector attached to the fuel pump.
* Safely Disconnect: Release the connector lock and carefully disconnect it from the pump. Inspect the terminals in the wiring harness connector and on the pump itself for corrosion or damage. Clean gently if needed.
* Set your multimeter to DC Volts (20V scale or similar).
* Turn the ignition key to "ON".
* Insert the multimeter probes into the wiring harness connector terminals that lead back to the machine's electrical system. You typically need to probe the power wire terminal (often indicated by color – refer to a wiring diagram if possible – Bobcat commonly uses red or red with a tracer for power, but DO NOT rely solely on color; probe the terminals while checking for voltage). The ground wire can usually be identified by a black wire or connection to the frame.
* You should see approximately +12 Volts DC on the power wire terminal when the key is "ON" (the pump circuit typically times out after the initial priming cycle – so test quickly after turning the key).
* Result: NO Voltage: Problem lies upstream – blown fuse (locate fuse box – check fuse related to fuel/engine control), faulty relay, ignition switch issue, or wiring break. Repair the power supply issue.
* Result: YES, 12V Present: Power is reaching the connector. Move on to testing the pump itself.

Test 3: Test Pump Motor Resistance (Ohm Test)
* Ensure the pump electrical connector is still DISCONNECTED from the machine's harness.
* Set your multimeter to measure Resistance (Ohms – lowest scale, like 200 Ohms).
* Touch the multimeter probes directly to the two metal electrical terminals on the fuel pump motor itself.
* A healthy fuel pump motor winding will typically show a resistance value between 0.5 Ohms and 5.0 Ohms (this range covers most common pumps). Consulting a specific service manual for the exact expected range is ideal.
* Result: Open Circuit (OL or 0L on multimeter): The internal motor winding is broken. Pump is dead.
* Result: Very High Resistance (far above 5 Ohms): Indicates worn brushes or internal damage. Pump is failing/failed.
* Result: Very Low Resistance (near 0 Ohms): Indicates an internal short circuit. Pump is dead.
* Result: Within Expected Range (e.g., 1-3 Ohms): The motor winding is likely electrically intact, meaning the pump should run if power is applied. If voltage was present during Test 2 but the pump wasn't running during Test 1, the issue could be mechanical failure within the pump (seized impeller, blocked internal check valves). This requires pump replacement.
(Optional but Recommended Test: Bench Test)
* If resistance is okay but you suspect a mechanical failure, you can carefully remove the pump. Attach temporary wires connected directly from the pump terminals to a known-good 12-volt battery (match polarity!). Exercise extreme caution: Fuel spills are a fire hazard. Do this outdoors away from sparks. If power is applied directly and the pump doesn't run quietly, it confirms mechanical failure.

Choosing a Replacement Bobcat 873 Fuel Pump

Once testing confirms pump failure, or if testing showed power but the pump isn't functioning mechanically, replacement is necessary. Here are your options:

OEM (Original Equipment Manufacturer) Pump:
- Pros: Guaranteed fit, exact specifications, comes with correct connector, maximum compatibility. Usually includes the mounting bracket or housing. Best quality assurance from Bobcat.
- Cons: Typically the most expensive option. May require purchasing through Bobcat dealers.
- Finding: Requires the Bobcat part number (often stamped on the pump housing or found via your serial number in a dealer parts lookup). Common Bobcat part numbers for the 873 lift pump include 6667302 or 6671070 (verify based on your serial number!). Order using the part number.
Quality Aftermarket Replacement Pump (Recommended Alternative):
- Pros: Significantly less expensive than OEM while often offering comparable quality and longevity. Widely available from reputable industrial equipment parts suppliers. Usually direct fit replacements. Many meet or exceed OEM specs.
- Cons: Varying quality exists – stick with well-known brands or suppliers recommended for Bobcat equipment.
- Finding: Search using "Bobcat 873 Fuel Pump Replacement" or the specific OEM part number your pump matches. Key suppliers include NAPA (look for Balkamp), Fleetguard, Delphi, Carter Pumps, or reliable online Bobcat parts specialists.
Avoid: Ultra-cheap, no-name pumps from questionable sources. These often fail prematurely due to poor materials and construction.

Essential Tools and Safety Precautions for Replacement

Safety First:
- Work outdoors or in a well-ventilated area.
- NO SMOKING or open flames anywhere nearby.
- Have a Class B (flammable liquid) fire extinguisher easily accessible.
- Wear safety glasses and gloves.
- Place absorbent pads or a container under the pump/fuel line connections to catch spills.
- Disconnect the NEGATIVE (-) Battery Cable before starting to prevent sparks.
Basic Tools Needed:
- Standard wrench set (SAE sizes: often 1/2", 9/16", 5/8" common for fuel line nuts)
- Screwdrivers (Flathead & Phillips)
- Pliers (Needlenose helpful)
- Multimeter (for testing harness before final connection)
- New Fuel Filters (Primary & Secondary) - Replace these NOW if not done recently!
- Clean fuel line disconnect tools (optional but helpful to prevent damage to plastic fittings on later models)
- Container to catch residual fuel
- Shop Towels
- New fuel hose clamps (if reusing old hoses - high-quality, fuel-rated worm gear clamps recommended)
- Thread Sealant specifically designed for diesel fuel fittings (if applicable, often used on inlet/outlet ports) - DO NOT use general-purpose pipe dope.

Step-by-Step Bobcat 873 Fuel Pump Replacement

Prepare & Access: Follow "Finding and Accessing" steps above. Raise and secure the cab. Disconnect negative battery terminal. Locate the pump.
Relieve Fuel System Pressure: While pressure is low on the suction side (around the lift pump), residual fuel will leak. Cover fittings immediately after opening with rags.
Disconnect Fuel Lines:
- Identify inlet (from tank) and outlet (to primary filter/engine) lines. Mark them if necessary (e.g., "IN" and "OUT" with tape).
- Place your container/catch pan under the connections.
- Carefully loosen the fuel line fittings at the pump ports using appropriate wrenches. Have rags ready. Disconnect both lines completely.
Disconnect Electrical Connector: Press the release tab (if present) and disconnect the wiring harness from the pump.
Remove Mounting Bolts: Remove the bolts or nuts securing the pump bracket or housing to the frame.
Remove the Old Pump: Carefully lift out the old pump assembly. Drain any remaining fuel into your container. Be mindful of any gaskets or seals left on the mount.
Prepare New Pump & Mounting Surface:
- Compare new pump to old one – ensure ports and connector match.
- Clean the mounting surface thoroughly. Remove any debris or old gasket material.
- If Applicable: Apply a thin coat of diesel-rated thread sealant ONLY to the male pipe threads of the pump's inlet/outlet ports. Avoid getting sealant into the port openings.
Install the New Pump:
- Position the new pump into the mounting bracket or directly onto the mounting location.
- Install and tighten mounting bolts/nuts securely but do not over-torque.
Reconnect Fuel Lines:
- Connect the fuel line from the tank (IN) to the pump's inlet port.
- Connect the fuel line to the primary filter/engine (OUT) to the pump's outlet port.
- Tighten all fittings securely using two wrenches to avoid twisting lines.
- Inspect: Ensure hoses are not kinked or rubbing sharply.
Reconnect Electrical Connector: Plug in the wiring harness connector firmly until it clicks/locks.
Re-pressurize & Prime (Critical Step - Reduce Cranking Time):
- Reconnect the negative battery cable.
- Turn the ignition key to "ON" and listen for the pump priming sound (hum/buzz for ~5-10 seconds).
- Wait a few seconds, then turn the key to "ON" again for another priming cycle.
- Repeat this "Key ON" (wait for pump to stop) cycle 3-4 times. This gradually fills the fuel lines and filter canister, purging a substantial amount of air before cranking the starter.
Attempt Start: Turn the key to "START". The engine might crank slightly longer than usual but should start much quicker than before if the pump was the issue.
Post-Start Check: Once running, carefully inspect all fuel line connections and the pump itself for any leaks. Listen for abnormal pump noises.
Bleed Air (if needed - usually minimized by priming cycles): If the priming cycles didn't clear all air and the engine runs rough after starting, the system might need manual bleeding per Bobcat 873 procedures (usually bleeding air at the injection pump bleed screw). Consult your machine's manual.

Maintaining Your Bobcat 873 Fuel System and Preventing Pump Failure

A failing pump isn't just an inconvenience; it causes downtime and lost productivity. Prevention is always better and cheaper:

Regular Fuel Filter Replacement: This is the NUMBER ONE preventive measure. Replace the primary (water separator) and secondary (final) fuel filters at least as often as recommended by Bobcat, or more frequently (e.g., every 250 operating hours) if working in dusty or humid conditions. Contaminants are a pump killer.
Use High-Quality, Clean Diesel Fuel: Avoid "bottom of the barrel" fuel sources. Use reputable suppliers. Consider adding a quality diesel fuel conditioner/stabilizer, especially for seasonal machines or if fuel sits, to combat water, lubricate the pump, and prevent microbial growth ("diesel bug").
Keep Water Out: Ensure fuel tank cap seals are intact. Drain water from the water separator (primary filter bowl) daily or before each use, as indicated by the warning light or float sensor (if equipped). Never let accumulated water sit in the separator.
Address Fuel System Leaks Immediately: Air intrusion on the suction side forces the pump to work harder and can cause premature failure. A leak after the pump is a fire hazard. Fix leaks as soon as they are noticed.
Keep the Fuel Tank Relatively Full: Minimizes condensation inside the tank, reducing water accumulation. Fill up at the end of the workday.
Guard Against Contamination: Use clean fuel containers and funnels. Never store fuel filters unwrapped. Keep the area around the fuel cap clean when opening.

Cost Considerations and Operation Time Expectations

Pump Cost: OEM pumps typically cost significantly more ( $150 -$ 300+ range). Quality aftermarket replacements are generally $50 -$ 150. Avoiding ultra-cheap pumps is wise.
Filter Cost: A primary and secondary filter set usually costs $30 -$ 75 depending on brand/quality. Essential investment.
Labor (DIY): For a reasonably experienced mechanic/owner, the entire process (diagnosis, access, replacement, priming) typically takes 1.5 - 3 hours, depending on familiarity with the machine. Allowing ample time avoids rushed mistakes.
Shop Labor: Dealerships or repair shops may charge 2-4 hours labor plus parts and filters. Diagnosis time may be extra.
Downtime Cost: This is often the largest hidden cost. Being equipped to diagnose and potentially replace the pump yourself can save days compared to waiting for a shop.

Q&A: Common Bobcat 873 Fuel Pump Questions

Q: Can I bypass the Bobcat 873 fuel pump?
- A: No. The engine relies on its positive flow to feed the injection pump. A failed pump or bypass will result in a no-start or severely degraded performance.
Q: Where is the fuel pump fuse or relay located?
- A: Fuses and relays are typically housed in a box on the engine or mounted to the frame/cab structure. Consult your specific operator's manual for the precise location and diagram identifying the fuse controlling the fuel pump circuit. It's often labeled "ECM," "Fuel Pump," or similar. Test or replace this fuse if troubleshooting indicates no power to the pump.
Q: Is the Bobcat 873 fuel pump submerged in the tank?
- A: No, the Bobcat 873 uses an externally mounted, inline electric lift pump. It's generally found near the fuel tank frame rail, not inside the tank.
Q: Why did my fuel pump fail?
- A: Common causes include running the pump dry frequently (low fuel, plugged filter), excessive contamination/wear from dirty fuel or clogged filters, water contamination causing corrosion, normal wear and tear after thousands of hours, electrical issues (shorts, low voltage), or manufacturing defect (less likely with reputable brands).
Q: What should the fuel pressure be on an 873?
- A: The lift pump provides low-pressure supply. While specific PSI numbers aren't usually critical for basic troubleshooting (listening, voltage, resistance tests are key), the typical target range for lift pumps like this is 4 to 8 PSI. Significant deviation outside this range indicates a problem, but testing pressure requires specialty gauges and adapters.

Conclusion: Ensuring Reliable Operation

Diagnosing a Bobcat 873 fuel pump problem requires a methodical approach: recognize the symptoms, systematically rule out other common causes like clogged filters, and perform straightforward electrical tests before replacing the pump. Locating the pump requires cab access, but the replacement process itself, when approached with the right tools, safety precautions, and following key steps like pre-priming, is manageable for most owners. Investing in a quality aftermarket pump is generally cost-effective, but never neglect the crucial role of regular fuel filter maintenance and clean fuel practices – these are your best defenses against premature fuel system failures. By understanding your Bobcat 873's fuel system and acting decisively when symptoms arise, you minimize costly downtime and keep your machine performing reliably job after job.

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