P0087 — Fuel Rail/System Pressure Too Low — 6.7 Cummins (EGR + DPF, pre-SCR)
Measured fuel rail pressure is below the PCM's commanded value on a 6.7L Cummins 2007.5–2012 (EGR+DPF, pre-SCR).
What it means
The PCM commands a rail pressure but the rail sensor reports lower than expected, indicating insufficient high-pressure fuel delivery or control on this CP3 common-rail system with in-tank lift pump.1
Most likely causes
- Low-side supply restriction / failing in-tank lift pump — Insufficient volume/pressure to the CP3 inlet causes the high-pressure pump to under-fill the rail. Typical on this platform with in-tank supply pump.12
- Fuel control actuator (FCA / MPROP) performance or electrical fault — FCA regulates CP3 output; a sticking or electrically degraded actuator can limit rail pressure. Related circuit code family includes P0090.3
- High-pressure pump (CP3) wear / internal leakage — A worn CP3 cannot build commanded pressure; catastrophic CP3 failure has been reported to cause engine stoppage.4
- Rail pressure sensor signal error — Erroneous low reading from the rail pressure sensor can set P0087. Sensor circuit high is P0193 on this platform.5
- Rail pressure relief / pressure-limiting valve leaking — Mechanical relief valve on the rail can leak, preventing pressure buildup. Platform has a mechanical rail pressure relief/pressure-limiting valve.1
How to diagnose
- Verify freeze-frame conditions and repeat the fault under load.
- Monitor live rail pressure vs desired rail pressure with a scan tool; confirm actual low pressure.
- Check low-side supply pressure/volume at CP3 inlet; evaluate in-tank lift pump performance.
- Inspect fuel filter/water separator condition and replace if restricted.
- Check FCA command % and electrical values; compare rail pressure response to FCA changes.
- Inspect rail pressure sensor voltage and compare to a known-good reference; consider P0193 correlation.
- Perform a controlled leak test of the rail pressure relief/pressure-limiting valve and injector return flow to identify internal leakage.
Parts and tools you may need
- Scan tool with live rail pressure and FCA data
- Fuel pressure test gauge for low-side supply
- Digital multimeter
- Fuel filter/water separator
Tools you’ll need
- OBD-II scan tool — Monitors live rail pressure vs desired rail pressure and FCA command to confirm low pressure under load.
- digital multimeter — Checks FCA coil resistance and rail pressure sensor voltage to rule out electrical faults.
- fuel pressure gauge — Measures low-side supply pressure/volume at the CP3 inlet to verify lift pump performance.
- fuel pressure test kit — Allows controlled rail pressure leak testing and injector return flow measurement to find internal leakage.
Rough cost and difficulty
| Likely repair | Parts | Shop labor | Who usually does it |
|---|---|---|---|
| Fuel filter service | $30–$150 | 0.3–1 hrs | Easy DIY |
| Fuel pressure control valve (FCA/regulator) | $100–$400 | 0.5–2 hrs | DIY with tools and a manual |
| Lift pump / fuel transfer pump | $100–$400 | 1–3 hrs | DIY with tools and a manual |
| High-pressure fuel pump | $700–$1,500 | 3–6 hrs | Shop |
Typical US independent-shop figures; labor runs about $120–$180 per hour (dealers charge more). Confirm the diagnosis before buying parts.
When to see a pro
If rail pressure remains low after supply and filtration checks, or if metal debris is suspected from CP3 failure, have a diesel technician inspect the high-pressure system before further operation.
Check for recalls
Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.
Sources
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