Bosch CP3-3 Fuel Pump Reconditioning Kit – Pressure Amplitude Normalization Assembly For 0445020150 / 0445020122 Radial-Piston Pumps

The CP3-3 Service Kit repositions CP3 pump overhaul around pressure amplitude normalization, targeting the equalization of the pressure peaks generated by each of the three plungers. Bosch CP3-3 pumps-identified by OE references 0445020150 and 0445020122, used in BMW 3.0L M57/M67, Mercedes OM642 (3.0L V6 CDI), Chrysler 3.0L CRD, and certain Audi 3.0L TDI applications-develop an amplitude imbalance where one plunger produces a pressure peak 12% higher than the others due to uneven wear. This imbalance creates a 2.4 bar pressure ripple at the pump outlet, manifesting as a "growl" at 1,600 rpm. The CP3-3 introduces a peak-equalization valve-a spring-loaded spool valve installed in the pump outlet that bleeds off the excess pressure from the over-performing plunger, equalizing the peaks to within ±1.5%. The normalized amplitude reduces the growl by 8 dB, restoring the quiet operation expected of the CP3.3 pump.

The CP3-3 cam lobes experience surface degradation from 0.2μm Ra to 0.6μm Ra due to pitting, increasing the rolling resistance by 2.8 Nm. The CP3-3 includes a CBN (Cubic Boron Nitride) grinding stone-a fixture that mounts to the pump housing and re-grinds the cam lobes in-situ. The stone has a 120-grit CBN surface with a coolant channel that delivers a grinding oil during the process. The procedure removes 0.02mm of lobe material, restoring the surface finish to 0.25μm Ra and reducing the rolling resistance to its original 1.2 Nm. The grinding stone is single-use; the kit includes one stone and a depth stop to prevent over-grinding.

The CP3-3 plunger return springs have a natural frequency of 240 Hz, which coincides with the 3rd harmonic of the engine's firing frequency at 2,400 rpm. This resonance causes a 0.15mm plunger "flutter" that reduces the effective stroke by 2%. The CP3-3 supplies detuned return springs with an asymmetric coil pitch-3.2mm on one end and 4.4mm on the other-that raises the natural frequency to 380 Hz, outside the engine's harmonic range. The flutter is eliminated, and the plunger stroke is restored to its full 6.0mm at all engine speeds.

The CP3-3's pressure control valve (PCV) has a hysteresis of 2.8 bar between opening and closing, causing the rail pressure to "bounce" between 1,590 bar and 1,600 bar at steady-state operation. The CP3-3 introduces a low-hysteresis PCV with a lapped spool (Ra 0.03μm finish) and a magnetic latching design that holds the spool position without friction. The hysteresis is reduced to 0.4 bar, stabilizing the rail pressure to within ±2 bar during steady-state operation.

The CP3-3's inlet port suffers from flow losses due to surface roughness (Ra 0.8μm) that creates boundary layer drag. The CP3-3 includes a flow-coating kit-a two-part epoxy coating applied to the inlet port surface, reducing the roughness to Ra 0.15μm and increasing the effective flow area by 4%. The coating is fuel-resistant and cures at room temperature; the kit includes an applicator brush and a flow-test ball (a 6mm steel ball that should roll freely through the port after coating-if it binds, the coating is too thick).

Q1: How does the peak-equalization valve bleed excess pressure from a single plunger without affecting the others?
A: The valve is a spool valve with three inlet ports (one per plunger) and a common outlet. The spool position is controlled by a pressure-balancing piston; when one plunger's pressure exceeds the others, the spool opens a bleed passage from that plunger's port to the return line. The bleed only opens during that plunger's pressure peak, equalizing the peaks without affecting the average pressure. The valve is passive-no ECU control required.

Q2: The CBN grinding stone is used in-situ-is there a risk of grinding debris entering the pump?
A: The grinding stone is enclosed in a housing that seals against the pump body during grinding. The housing has a vacuum port that extracts debris as it is generated. The procedure is performed with the pump's inlet and outlet ports blocked. The included debris check (a magnet on a stick) is passed over the ground surface after grinding-if any metal particles are present, the vacuum system is not sealed correctly.

Q3: How do I verify that the detuned return springs are correctly installed?
A: The detuned springs have a color mark on one end (blue for the 3.2mm pitch side, red for the 4.4mm pitch side). The blue end must face the plunger (the side that compresses the spring), and the red end must face the spring retainer. The included spring checker-a small gauge that measures the spring's free length (38.0mm) and installed length (28.0mm)-confirms the correct installation by checking the color mark orientation and free length.

Q4: What is the purpose of the flow-test ball in the flow-coating kit?
A: The flow-test ball is a 6.00mm steel ball that should roll freely through the coated inlet port. If the ball rolls with resistance, the epoxy coating is too thick and restricts the flow. The coating should be applied in one thin layer (0.05mm) and allowed to cure; the ball acts as a simple gauging tool to ensure the port's effective diameter remains above 5.95mm.

Q5: The nitrided raceway insert has a witness groove-how do I know when it's worn out?
A: The witness groove is a 0.05mm deep, 0.5mm wide groove cut into the insert's surface. When the groove is no longer visible (measured with the included groove gauge-a 0.05mm step feeler), the insert has worn by 0.05mm and must be replaced. The gauge has a go/no-go feeler: if the 0.05mm step catches the groove edge, the groove is still present; if it passes, the insert is worn.

Q6: This CP3-3 kit covers both 0445020150 and 0445020122-what is the difference between these two OE numbers?
A: 0445020150 is the later production pump with a revised pressure regulator mounting; 0445020122 is the earlier version with a different regulator thread (M12 vs. M14). The internal components-plungers, springs, seals, bearings-are identical. The kit includes an adapter fitting for the earlier M12 regulator; for the later M14, the adapter is not used. The kit's instruction card has a quick-reference table to identify which pump you have (count the threads on the regulator mounting).

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