DTC P0087 – Fuel Rail / System Pressure Too Low.
Useful for petrol and diesel engines.

✅ P0087 – Meaning

The ECM detects that actual fuel rail pressure is lower than commanded pressure for a specific amount of time.
This indicates insufficient fuel supply or leakage in the fuel system.

🚗 Common Symptoms

Hard starting / long crank

Engine hesitation or stalling

Low power under load

Limp mode

Misfire under acceleration

Fuel pump whining

🔧 Common Causes

1. Low fuel supply problems

Weak low-pressure pump (in tank)

Blocked or restricted fuel filter

Clogged fuel strainer

Leaking or cracked fuel lines

2. High-pressure system problems

Weak high-pressure pump (HPFP)

Faulty fuel rail pressure sensor

Faulty fuel pressure control valve / IMV / SCV

Excessive injector return (leaking injector)

3. Electrical issues

Poor connection to HP pump control valve

Open/short wiring to LP or HP pump

Ground issues

Low battery voltage

🧪 Step-by-Step Professional Diagnostic Procedure

Step 1: Check Fuel Quantity & Basic Supply

👉🏻 Check fuel level
👉🏻 Listen for in-tank fuel pump priming (2–3 seconds on key-ON)
👉🏻 Check for restricted fuel filter (diesel filters often clog)

> If filter is older than 10k–15k km → Replace first

Step 2: Scan Tool Live Data

Monitor:

A. Commanded vs Actual Rail Pressure

Idle expected: 250–350 bar (diesel)

Acceleration expected: 900–1600 bar

Petrol GDI expected: 40–150 bar

If actual is consistently low → fuel supply issue.

B. Low Pressure (LP) Pump Reading (if available)

Diesel LP: 4–6 bar
Petrol LP: 3–4 bar

If LP is low → suspect in-tank pump, filter, or blockage.

Step 3: Check Injector Return Flow (Diesel)

One or more injectors returning too much fuel will drop rail pressure.

👉🏻 Perform injector leak-off test
👉🏻 Any injector returning significantly more → replace

Step 4: Test Pressure Control Components

A. IMV / SCV (Suction Control Valve)

Symptoms when faulty:

Rail pressure fluctuates

Hard start

Low pressure under load

Test:

Check wiring

Check coil resistance

Command test via scan tool (if supported)

B. Pressure Relief Valve

If stuck open → pressure cannot build.
Check for diesel leakage at return line.

Step 5: Check High-Pressure Pump

Indications of HP pump failure:

Low pressure even with LP pump normal

Metal shavings in fuel filter

Poor pressure rise during acceleration

If metal flakes exist → full fuel system clean + injector flush required.

Step 6: Electrical Inspection

👉🏻 Check voltage at in-tank pump
👉🏻 Check wiring to HP pump control valve
👉🏻 Check fuse & relay for LP pump
👉🏻 Check ECM ground points

🛠️ Most Common Repairs

Replace fuel filter

Replace weak low-pressure (LP) pump

Replace SCV / IMV on HP pump

Repair leaking fuel line

Replace high-pressure pump (HPFP)

Replace leaking injector(s)

Replace fuel rail pressure sensor (less common)

⚠️ Important Notes

On diesel engines (especially CRDI), injector leak-off is one of the most common causes.

If HP pump fails with metal shavings → never install new injectors without flushing entire system.

Welcome To Madurai Car Service 💐🙏.