Direct Answer: To resolve cylinder misfires and injection pressure drops on DAF XF105, CF85, and CF75 trucks, mechanics must physically test the 1668325 Electronic Unit Pump (Delphi BEBU5A00000) for plunger scoring and solenoid resistance. Upgrading obsolete 1625753 units to OE-calibrated 1668325 pumps restores exact hydraulic tolerances across PACCAR MX 12.9L and PR 9.2L engines.
EUP Engineering & Mechanical Stress in PACCAR Engines
The 1668325 Electronic Unit Pump (EUP), manufactured under Delphi reference BEBU5A00000, is the primary high-pressure generation component for Euro 4 and Euro 5 DAF commercial fleets (2006-Onwards). Engineered specifically to work in tandem with DAF’s Smart Injector architecture, each individual unit pump is driven directly by the engine camshaft on PACCAR MX (12.9L) and PACCAR PR (9.2L) platforms. Because DAF superseded the older 1625753 part number with the reinforced 1668325 (and compatible 2135456) design to handle continuous high-bar pressures, running degraded pumps leads to severe hydraulic lag, internal fuel bypassing, and camshaft roller wear.
Physical Failure Modes & Diagnostic Indicators
| System Fault / Symptom | Mechanical Root Cause | Impact on PACCAR MX / PR System |
|---|---|---|
| Peak Torque Loss & Cylinder Misfire | Plunger & Barrel Micro-Scoring | Abrasive fuel particles erode the micron-level clearance inside the 1668325 pumping chamber, causing internal pressure bleed-off before the Smart Injector can open. |
| Dead Cylinder / Thermal Cut-Out | EUP Control Valve Coil Breakdown | Extreme thermal cycling on the engine block degrades the internal solenoid winding, preventing the spill valve from closing to build injection pressure. |
4-Step Hardware Isolation & Bench Verification Protocol
In an EUP + Smart Injector system, mechanics must physically isolate whether pressure loss originates from the 1668325 unit pump or the downstream injector. Follow this strict mechanical testing sequence:
- Static Coil Resistance Verification: Disconnect the engine harness from the 1668325 EUP terminal. Use a precision digital multimeter to measure resistance across the solenoid pins at both ambient and hot engine temperatures. Any open circuit or dead short confirms internal coil failure.
- Exhaust Manifold Thermal Profiling: Under load, scan each exhaust port on the PACCAR MX or PR cylinder head using an infrared pyrometer. A substantially cooler exhaust port pinpoints the exact cylinder where the EUP is failing to deliver pressurized fuel.
- High-Pressure Line & Seal Inspection: Inspect the short high-pressure delivery pipe connecting the EUP to the Smart Injector, along with the external viton O-rings on the pump body. Ruptured O-rings allow low-pressure supply fuel to leak externally or dilute crankcase oil.
- Tappet Roller & Cam Lobe Examination: Upon extracting the 1668325 unit pump from the engine block, physically inspect the bottom roller tappet and spring assembly for spalling, flat spots, or binding. Always verify the camshaft lobe surface is free of pitting before seating the replacement unit.
OE Supersession & Exact Fleet Fitment Data
Gottoparts supplies rigorously bench-calibrated EUP units built to exact Delphi and DAF metallurgical standards. Verify your Euro 4 / Euro 5 commercial truck fitment using the official engineering cross-reference table below.
| Category | Part Number | Application (Machine / Engine / System) |
|---|---|---|
| Delphi Part No. | BEBU5A00000 | Electronic Unit Pump (EUP) — Works with Smart Injector |
| DAF OEM (Active) | 1668325 | DAF XF105 / CF85 / CF75 Truck (Euro 4 / Euro 5, 2006-Onwards) |
| DAF OEM Supersession | 1625753 / 2135456 | 1625753 (Replaced by 1668325) | 2135456 (Compatible Number) |
| Truck & Engine Models | CF85 / XF105 / CF75 |
DAF CF85 & XF105: Engine PACCAR MX (12.9L) DAF CF75: Engine PACCAR PR (9.2L) |
What is the Delphi part number and supersession history for the DAF 1668325 unit pump?
The DAF 1668325 Electronic Unit Pump (EUP) is manufactured by Delphi under part number BEBU5A00000[cite: 9]. Within the DAF OEM catalog, 1668325 directly replaces the older part number 1625753 and is cross-compatible with DAF part number 2135456.