CAT 320D Fuel Pump Adapter / Solenoid Assembly – Fit For 326-4635 Pump (312-5620 / 32F61-10302)

On a CAT 320D, the fuel system doesn't fail loudly at first-it loses control. You may feel delayed throttle response, unstable idle, or sudden derate long before the pump itself is diagnosed. In many cases, the real culprit is the fuel pump control "adapter" (electronic solenoid / metering actuator assembly) mounted on the high-pressure pump. This 320D adapter is widely sold as Solenoid Valve 312-5620, designed for the C6.4/C6.6 fuel pump 326-4635 and related pump references such as 32F61-10302

 

 

Despite the nickname "adapter" used in many aftermarket channels, this component functions as the electronic control unit on the pump-regulating fuel delivery into the pumping elements so rail pressure can follow ECU targets. When it reacts quickly and seals correctly, the pump builds pressure smoothly; when it sticks, leaks internally, or weakens electrically, rail pressure can swing-leading to power loss and fault codes.

Many listings describe this part as an electronic solenoid valve complete assembly for CAT 320D fuel pump systems.

 

 

Customers rarely search "CAT 320D pump controller." They search what's on the old part or the quote sheet:

312-5620  

Fits fuel pump 326-4635 (common fitment pairing in product listings) 

Also referenced with pump numbers 32F61-10302 and 10R-7662 in some aftermarket catalogs 

If your Google independent site places "312-5620 + 326-4635 + 320D" in the title, first paragraph, and a dedicated "Cross Reference" section, you'll match how technicians actually search during troubleshooting.

◆ Typical fitment: where this part is commonly used

This adapter/solenoid assembly is commonly marketed for:

Caterpillar 320D excavator fuel systems

CAT C6.4 / C6.6 engine applications using the 326-4635 pump 

Some listings also mention Perkins / CAT 1106 compatibility in the same pump-control family, depending on pump configuration and market starsdiesel 

Because Caterpillar machines can vary by serial range and pump version, the best practice is to confirm fitment by matching the number on your existing unit (312-5620 or the pump number 326-4635) rather than relying only on "fits 320D" text.

 

 

Workshops like this component because it addresses the kind of problems that waste hours:

✓ Restores rail-pressure stability (helps eliminate hesitation, uneven acceleration, and pressure deviation)
✓ Reduces downtime compared with replacing the entire pump when the pump's mechanical core is still healthy
✓ Improves start quality when hard-start symptoms are driven by poor metering response
✓ Cost-effective repair path for fleet and contractor machines

Many sellers position it as a direct replacement that matches the original function for the 320D pump system 

◆ Common symptoms (great for SEO + customer self-diagnosis)

Include these phrases naturally-buyers often search them before they know the part number:

● Hard starting / long crank (especially warm)
● Sudden derate or limp mode with fuel pressure control faults
● Power loss under load; machine feels "flat" during digging or travel
● Unstable idle or hunting RPM
● Pump-control related electrical issues (connector heat damage, intermittent response)

If a customer already replaced filters and checked supply fuel, this adapter/solenoid becomes a high-probability fix.

 

 

➤ New, ready-to-install assembly for the 326-4635 pump family
➤ OE-style connector housing and mounting flange (simple bolt-on replacement)
➤ Designed for harsh off-highway conditions (heat, vibration, long operating hours)
➤ Ideal for service shops rebuilding or maintaining CAT 320D fuel systems

 

 

Confirm the pump model (326-4635) and the solenoid reference 312-5620 before ordering.  

Keep the work area clean-common rail systems are contamination-sensitive.

After installation, verify rail pressure response and check for leaks; a quick diagnostic scan can confirm stable regulation.

 

 

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