Stanadyne Service Bulletin 398R1

Supersedes Bulletin 398 dated 03/15/1984

Housing Pressure Regulator Fittings

The housing pressure return line connectors currently used in “D” series pumps are listed in the following chart. The operating pressure for each regulator fitting, the type of fitting, and the thread sizes are also provided in this chart. Housing pressure is normally checked at the full load rated speed and pressure fluctuations up to 2 psi are considered acceptable. Always refer to the individual pump specification for exact parameters.

P/NTypeGovernor Cover EndReturn Line EndPressure Range (PSI)
13265Brass Elbow1/8-27 NPT7/16-20 External Thread
& 45° Flare
6.0 – 12.0
15830Steel, Straight1/8-27 NPT1/8-27 NPT Internal Thread6.0 – 12.0
16800Brass Elbow1/8-27 NPT1/2-20 External Thread
& 45° Flare
6.0 – 12.0
17356Steel, Straight1/8-27 NPTPush on Barb for 1/4” I.D.
6.0 – 12.0
20154Steel, Straight1/8-27 NPT1/8-27 NPT Internal Thread10.0 – 20.0
21251Steel, Straight7/16-20 UNF1/8-27 NPT Internal Thread6.0 – 12.0
22109Steel, Straight7/16-20 UNF1/8-27 NPT Internal Thread8.0 – 12.0
23183Steel, Straight
for use with HPCA
7/16-20 UNFPush on Connection for
1/4” I.D. Hose
8.0 – 14.0
23645*Steel, Straight
for use with HPCA
7/16-20 UNF1/8-27 NPT Internal Thread8.0 – 14.0
26564Steel, Straight7/16-20 UNFM12 x 1.56.0 – 14.0
28973Steel, Straight7/16-20 UNFM12 x 1.56.0 – 10.0
40998Steel, Straight7/16-20 UNFM12 x 1.58.0 – 12.0
42429Steel, Straight7/16-20 UNFM12 x 1.512.0 – 21.0
*Supersedes 23530 and 22853, contains stainless steel spring

Housing pressure should be checked with a dampened pressure gauge, calibrated from 0-30 psi (0-207 kPa) with graduations of 1.0 psi (7 kPa) and an accuracy of plus or minus 0.5 psi (3.5 kPa). This gauge is attached to the available housing pressure port on the 39938 Electronic Advance Indicator. Reference Service Bulletin 562R1 for details.

Note: Fittings with 7/16-20 UNF external threads on the governor cover end are to be used with O-ring seal p/n 27607.

Jimmy Finch

Dallas Branch Manager, M&D Distributors

Jimmy Finch has over 33 years of experience in Diesel Engine Sales, Service and Repair. His experience started early in life at Texas Fuel Injection Service (an early acquisition of M&D) as a job with a means to an end. Somewhere in that 33 years this job turned into a fulfilling career. He started in the injector clean up department and has held practically every position leading up to his current role as Branch Manager of the Dallas, Texas location.

In his spare time, Jimmy enjoys spending time with his wife of 24 years, Priscilla. They are currently getting ready to make their way into the empty-nesters stage of life. He also enjoys the occasional hunting trip with friends and family and chasing down potential customers by the names off their trucks.

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