PAI 645050 Fuel Check Valve – Detroit Diesel Series 60 12.7L 14L

The PAI 645050 is a premium aftermarket fuel pump check valve designed for Detroit Diesel Series 50 and Series 60 engines. This valve is a critical component in the fuel system that prevents fuel from draining back to the tank when the engine is shut off, ensuring reliable starts and proper fuel pressure. PAI Industries manufactures this valve in the USA to meet or exceed OEM specifications, backed by their 2-year unlimited mileage warranty.

Signs You Need a New Fuel Check Valve

• Hard starting or extended cranking, especially after sitting overnight
• Engine cranks but won't start until after prolonged cranking
• Fuel system loses prime after engine shutdown
• Air in fuel system causing rough running or stalling
• Fuel draining back from injector lines after shutdown
• Inconsistent fuel pressure readings
• Engine starts fine when warm but struggles when cold
• Fuel filter bowl level drops after engine is turned off

Specifications

Cross References

This part replaces or is equivalent to the following part numbers:

• PAI: 645050
• Detroit Diesel: 23516993
• Alternate: A-23516993, A23516993, DDC23516993

Engine Applications

This fuel check valve fits the following Detroit Diesel engines:

• Series 50 8.5L: All years
• Series 60 11.1L: 1987-1998
• Series 60 12.7L: 1987-2007 (DDEC I through V)
• Series 60 14.0L: 2001-2011 (DDEC IV through VI)

Vehicle Applications

The Detroit Diesel Series 60 engine was installed in Class 8 trucks, buses, and coaches from major manufacturers:

• Freightliner: FLD, Classic, Century, Columbia, Coronado, Argosy (1987-2011)
• Kenworth: W900, T800, T600, T660, T2000 (1987-2011)
• Peterbilt: 379, 378, 377, 385, 386, 387, 389 (1987-2011)
• International: 9200, 9300, 9400, 9600, 9900 (select years)
• Volvo: VN Series, WIA, WG (select years)
• Western Star: 4900 Series (select years)
• Sterling: A-Line, L-Line (select years)
• Transit Buses: MCI, Prevost, New Flyer, Gillig, NABI
• Motor Coaches: Prevost, MCI, Van Hool, Blue Bird
• RV/Motorhomes: Monaco, Newmar, Country Coach, Newell

How the Fuel Check Valve Works

The fuel check valve is located in the fuel system between the fuel pump and the fuel return line. When the engine is running, the fuel pump draws fuel from the tank and circulates it through passages in the cylinder head to supply the unit injectors. Excess fuel returns to the tank through the return line. The check valve contains a spring-loaded mechanism that allows fuel to flow in one direction only. When the engine is shut off, the check valve closes to prevent fuel from draining back out of the fuel galleries in the cylinder head. This keeps the fuel system primed and ready for the next start. If the check valve fails, fuel drains back to the tank, causing air to enter the fuel lines and resulting in hard starting or no-start conditions, especially after the vehicle has sat for extended periods.

Installation Notes

Before replacing the fuel check valve, verify the valve location on your specific engine application. On some Series 60 installations, the check valve may be located in the fuel return line near the fuel tank rather than on the back of the engine. Use thread sealant appropriate for fuel system applications. After installation, prime the fuel system and verify there are no leaks before starting the engine. If hard starting issues persist after replacing the check valve, inspect fuel lines for cracks, loose connections, and check injector O-rings for leaks.

Verify your engine serial number and fuel system configuration to confirm application before ordering. Location of the check valve may vary by chassis manufacturer and fuel system layout.

Handling Time
At All Pro Truck Parts we do our best to ship all orders same day for orders placed before 12:00pm Central Standard Time. Same day shipment is never guaranteed. For standard UPS or USPS shipping, you will typically receive your package in 1 - 5 business days. Shipping times are never guaranteed and All Pro Truck Parts is not responsible for lost or delayed shipments by the carrier. Carrier times vary by distance from shipment origin and may change without prior notice. Shipping price is calculated from package dimensions and weight. Calculated rates for orders will be available at checkout. Orders placed after 12:00pm CST on Fridays will not be fulfilled until the following business day, Monday morning barring a holiday.

Next Day Air Shipments
The cutoff time for UPS Next Day Air is 12:00PM. If you have missed the cutoff time but would still like to place an order for Next Day delivery, please send us a text message or email. We can try to accommodate and ship your order from another warehouse.

Incorrect Shipping prices
All Pro Truck Parts reserve the right to cancel any order, in the event shipping rates are calculated incorrectly at checkout. We will notify you at your provided contact information to give you the option to pay the correct amount, or allow you to cancel the order for a full refund. 

Free Shipping
Select products qualify for free shipping. Qualifying product groups can change without notice. Free shipping will be shipped via UPS Ground, USPS First Class or USPS Priority Mail.  

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Returns
All Pro Truck Parts offers lifetime returns for any reason on NEW, UNOPENED items in the original packaging with exceptions. (See sale items and special order items).
To be eligible for a return, your item must be unused and in the same condition that you received it. It must also be in the original packaging.

Used items (if applicable)
Items marked as USED at the time of sale will be accepted for return up to 30 days from the date of sale. 

Defective items (if applicable)
Defective items under manufacturer warranty will be eligible for return, as well as a full refund for the total amount paid by the customer. The following criteria must be met to be eligible. (a). The part is under manufacturer warranty (b). the manufacturer has determined the part defective for the purchased application. 

Refunds (if applicable)
Once your item is returned and received and inspected, we will send you an email to notify you that we have received your returned item. We will also notify you of the approval or rejection of your refund.
If approved, then your refund will be processed, and a credit will automatically be applied to your credit card or original method of payment, within 7 business days. For order placed by phone through a card terminal, you must call in to initiate the refund. 

Late or missing refunds (if applicable)
If you haven’t received a refund yet, first check your bank account again.
Then contact your credit card company, it may take some time before your refund is officially posted.
Next contact your bank. There is often some processing time before a refund is posted.
If you’ve done all of this and you still have not received your refund yet, please contact us at sales@allprotruckparts.com.

Sale items (if applicable)
Only regular priced items may be refunded, unfortunately sale items cannot be refunded. 

Special Order Items (if applicable)
Special order items may be eligible for a refund. The decision to accept a special order item for refund is left solely to the All Pro Truck Parts management team. 

Exchanges (if applicable)
We only replace items if they are defective or damaged. If you need to exchange it for the same item, send us an email at sales@allprotruckparts.com and send your item to: All Pro Truck Parts, 3948 Interstate 30 W, Caddo Mills TX 75135, United States.

Shipping
To return your product, you should mail your product to: All Pro Truck Parts, 3948 Interstate 30 W, Caddo Mills TX 75135, United States

You will be responsible for paying for your own shipping costs for returning your item. Shipping costs are non-refundable.

Depending on where you live, the time it may take for your exchanged product to reach you, may vary.

If you are shipping an item over $75, it is advised that you use a trackable shipping service or purchasing shipping insurance. We don’t guarantee that we will receive your returned item.
For returned items designated as "Free Shipping", any items shipped to the customer in which the customer did not pay shipping. All Pro Truck Parts will recover the cost of shipping to the customer's address from the refundable amount owed to the customer on the return and inspection of the item.