International DT466 – HARD START AND NO START DIAGNOSTICS – Test Procedures – Fuel Pressure and Aerated Fuel - Diesel Engines Troubleshooting (2025)

Purpose
To check for correct fuel pressure and aerated fuel
NOTE: Do the following:
• Ask the operator if the amber WATER IN FUEL lamp was on during vehicle operation.
• If engine has an optional Engine Fuel Pressure (EFP) sensor, ask the operator if the amber FUEL FILTER lamp was on during vehicle operation. If the lamp was on, change the fuel filter and retest for poor engine operation.
• If unit was run out of fuel, make sure the fuel system was primed. See “Priming the Fuel System” in Section 4 (page 132) for procedure.
• See “Combustion Leaks to Fuel” in Section 4 (page 104) if all three of the following conditions are noted:
• Fuel system will not prime
• White to black exhaust smoke
• Pulsating fuel pressure

Tools
• Fuel pressure test gauge
• Fuel Pressure Test Kit
• 1 to 5 gallon bucket
• Fuel/Oil Pressure Test Coupler

Fuel Pressure
Procedure

1.See “DT 466 Performance Specifications” – Appendix A (page 595) or “DT 570 and HT 570 Performance Specifications” – Appendix B (page 619) for fuel pressure specifications and record on Diagnostic Form.
NOTE: If engine is equipped with optional Engine Fuel Pressure (EFP) sensor, use EST with MasterDiagnostics® software to monitor fuel pressure. Compare the EST values to gauge readings.

CAUTION: Be sure to place a rag or suitable container under the fuel pressure test valve when bleeding the
fuel rail. Dispose of fuel in a correct container clearly marked DIESEL FUEL according to local regulations.

NOTE: Engine fuel can be a threat to the environment. Never dispose of engine fuel by putting it in the trash,
pouring on the ground, in the sewers, in streams, or bodies of water.

NOTE: Engines are equipped with a fuel pressure test valve in the form of either a Shrader valve or a
diagnostic coupling.

NOTE: If the engine is equipped with a Shrader valve, use the Fuel Pressure Test Adapter.

NOTE: If the engine is equipped with a diagnostic coupling, adapt the Fuel/Oil Pressure Test Coupler to
the Fuel Pressure Gauge.

2. Connect Fuel Pressure Gauge with shut-off valve and clear 3/8” diameter hose to test valve.
3. Route the clear hose into a drain pan.

4. Start or crank the engine for 20 seconds. Measure the fuel pressure with the shut-off valve closed.
Open the shut-off valve to check for aeration.

NOTE: Breaking any fuel system joint will induce air into the fuel system. The air should pass in a short period of time. As fuel pressure is relieved, a steady stream of fuel without air bubbles indicates the fuel is not aerated.

NOTE: If a Fuel Pressure Gauge with shut-off valve and clear 3/8” diameter hose is not available to check for aeration, see alternative test “Checking for Aerated Fuel using Spare Fuel Line.”
5. Record results on Diagnostic Form.
• If fuel pressure is below specification and fuel is not aerated, replace the fuel filter and clean the strainer. Test the fuel pressure again.
• If fuel is aerated, see “Aerated Fuel” in Section 4.
• If fuel pressure is still low and fuel is not aerated after replacing the fuel filter and cleaning the strainer, do “Operation of the Fuel Pump Test.”
• If fuel pressure is in specification and the fuel is not aerated, do not continue testing the fuel system. Continue to the next diagnostic test.

Possible Causes
No fuel
• Low fuel level in fuel tank
• Debris in tank can cause high-restriction and low fuel pressure.
• Inline fuel valve (if equipped) could be shut-off
• Failed seals or fuel lines between fuel tanks
• Ice in fuel lines
• Inoperative fuel tank transfer pump
• Fuel tank pickup tube cracked

Low fuel pressure
• Dirty filter element
• Debris or rust in fuel strainer

• Restriction from the fuel tank to the fuel filter housing inlet can cause high-restriction and low fuel pressure.
• Plugged supplemental filters or water separators can cause high-restriction and low fuel pressure.
• Debris in tank can cause high-restriction and low fuel pressure.
• A kinked or bent fuel supply line or a blocked pickup tube can cause high-restriction and low fuel pressure.
• Waxed or jelled fuel in the fuel filter will cause high-restriction and low fuel pressure. (Usually Grade 2-D)
• Ice in fuel lines.
• A restriction between the fuel inlet fitting, strainer, and fuel pump can cause high-restriction and low fuel pressure.
• Debris in the fuel regulator valve
• Failed fuel pressure regulator valve.
• Failed fuel pump
• Failed high-pressure oil pump (can not operate fuel pump)

Aerated fuel
• Failed seal for inlet fitting in fuel filter housing
• Supply filter or water separator leaking
• A loose fuel line on the suction side of the fuel system can ingest air into the system and cause low fuel pressure (most noticeable under load).
• Strainer drain valve loose or damaged
• Strainer bowl warped or damaged
• Missing O-ring from strainer bowl
• Damaged seals on steel inlet tube to fuel pump
• Primer pump seals damaged

Fuel restriction
• Dirty filter element
• Debris or rust in fuel strainer

• Restriction from the low-pressure fuel filter housing inlet to the fuel tank can cause high-restriction and low fuel pressure.
• Plugged supplemental filters or water separators can cause high-restriction and low fuel pressure.
• Debris in tank can cause high-restriction and low fuel pressure.
• A kinked or bent fuel supply line or a blocked pickup tube can cause high-restriction and low fuel pressure.
• Waxed or jelled fuel in the fuel filter will cause high-restriction and low fuel pressure. (Usually Grade 2-D)
• Ice in fuel lines.
• A restriction between the fuel inlet fitting, strainer, and fuel pump can cause high-restriction and low fuel pressure.

High fuel pressure (pulsating fuel pressure)
• Debris in the fuel regulator valve
• Inoperative fuel pressure regulator valve.
• Combustion gases leaking into fuel system

Checking for Aerated Fuel using Spare Fuel Line

NOTE: This is an alternative test. Do this procedure, only if Fuel Pressure Gauge with shut-off valve is not available.
Tools
• Spare fuel line (filter housing to fuel supply pump)
• Clear plastic line
• Hose clamp (2)

Procedure

1. Remove fuel supply line from suction side of fuel pump and fuel filter housing.

2.Make a test fuel line.
• Use spare fuel line. (Make sure both sleeve seals are good.) Cut a 3 inch section from the center of the fuel line. Install clear plastic line in place of removed section and secure plastic line with clamps.

NOTE: The mechanic is expected to keep the fuel test line for future diagnostics. Expense the fuel test line as an essential tool and keep it with other diagnostic tools. Warranty will not cover the cost of the fuel test line.

3. Install test fuel line.
NOTE: Verify that sleeve seals are in good condition.
4. Do one of the following:
• For Hard Start and No Start Diagnostics, crank engine for 20 seconds and check for air bubbles in the clear plastic line.
• For Performance Diagnostics, run engine at high idle, no load and check for air bubbles in the clear plastic line.
5. Record results on Diagnostic Form.
NOTE: Initially, fuel will be aerated due to draining fuel from filter housing and strainer in previous test.
• If fuel is aerated check for a leak in the suction side of fuel system. See “Aerated Fuel” in Section 4.
• If fuel is not aerated and fuel pressure is good, continue with next test.
• If fuel is not aerated and fuel pressure is low, do “Operation of Fuel Pump”.
6. Remove fuel test line and install original fuel line.
NOTE: Verify that sleeve seals are in good condition.

Operation of Fuel Pump
Tools
• Vacuum Pump And Gauge (kit)
• Hose clamp
• Fuel pressure test gauge
• Fuel Pressure Test Kit
• Fuel/Oil Pressure Test Coupler
• 1 to 5 gallon bucket

Procedure

NOTE: The fuel pressure gauge with the inline shut-off valve is still connected to the fuel pressure test valve.
If shut-off valve is not opened, test will result in false readings. Do the following procedure:
1. Open the shut-off valve.
2. Disconnect fuel line (suction side) from fuel filter housing.

When routing test line, do not crimp the line, run the line too close to moving parts, or let the line touch hot engine surfaces.
3. Slide test hose onto fuel line and secure with hose clamp or use cone adapter (vacuum pump kit) that fits into end of fuel line.

4. Insert vacuum pump nozzle into test hose.
5. Crank engine, check gauge reading, and record on Diagnostic Form.
• If less than 12 in Hg., check steel line and test connections between the air vacuum test gauge and fuel pump. Verify integrity of test hose adapter
• If vacuum is still below specification, replace the fuel pump following procedures in the Engine Service Manual.
• If greater than 12 in Hg., the fuel pump is working. Replace fuel regulator and retest fuel pressure.
• If fuel pressure is still low after replacing the fuel pump and regulator, check for restriction between the filter housing and fuel tank.