If you own a 2004–2006 Sprinter with the OM647 engine and you're smelling diesel or spotting fuel under the van, don't panic — and don't assume the worst. One of the most common fuel leaks on these engines comes from something simple: loose bolts on the back of the high pressure fuel pump (HPFP).
This is a fix you can do yourself with basic hand tools. Here's the full rundown.
Symptoms: How to Tell It's the HPFP Bolts
- Diesel fuel smell, especially after driving
- Wet fuel around the high pressure fuel pump area (driver's side of the engine)
- Fuel dripping down the back of the engine
- No check engine light (this is a mechanical leak, not a sensor issue)
If you're seeing fuel but the van still runs fine, loose HPFP bolts should be high on your suspect list.
Where the Leak Hides
The high pressure fuel pump sits on the driver's side of the OM647 engine. The bolts on the back of the pump work themselves loose over time from engine vibration — and once they back out enough, fuel starts seeping past the sealing surfaces.
You can't easily see these bolts with everything in place, which is why this leak gets misdiagnosed. The pump needs to come off to get proper access.
What You'll Need
- Basic socket set (metric)
- Torque wrench
- Replacement seals/gaskets for the HPFP (inspect when removed)
- Fuel pump elbow kit (replace while you're in there — the elbows get brittle)
- New serpentine belt (you're removing it anyway; cheap insurance)
Step-by-Step: Removing the HPFP and Tightening the Bolts
- Disconnect the battery. Always first when working around fuel.
- Remove the serpentine belt. You'll need the belt off to access the pump. Note the routing before removal.
- Disconnect the fuel lines from the HPFP. Have rags ready — fuel will drip.
- Unbolt the HPFP from the engine. Keep track of bolt positions.
- Inspect the back of the pump. You'll see the bolts that worked loose. Check the sealing surfaces for damage.
- Clean everything. Wipe down the mating surfaces on both the pump and engine.
- Reinstall with proper torque. Tighten the HPFP mounting bolts to 124 in-lb (~14 Nm) and the high-pressure fuel line fitting to 194 in-lb (~22 Nm) — don't just crank them down.
- Replace the fuel pump elbows while you're in there. They're cheap and they fail.
- Reinstall the pump, reconnect fuel lines, reinstall the serpentine belt.
- Reconnect the battery, prime the fuel system, and check for leaks.
Pro Tip: Do This With Cooling System Work
This job is MUCH easier with the radiator removed — you get real working room instead of fighting in tight quarters. If you're already planning cooling system maintenance (hoses, thermostat, water pump), stack this job on top of it. Two birds, one teardown.
Parts You'll Need
All available at MillionMileSprinter.com:
- Fuel Pump Elbow Kit — replace these while the pump is off; the originals get brittle and crack
- Serpentine Belt (OM647) — you're removing it anyway, don't reinstall a worn belt
- HPFP seals/gaskets — inspect and replace as needed
Watch the Video
This guide pairs with the full video walkthrough showing exactly where these bolts are and how the pump comes off: Watch on Instagram
Have a Sprinter issue you're stuck on? Browse our full parts catalog at MillionMileSprinter.com — we stock parts for all years of Sprinter vans.