Allmand — Relief Valve Pressure Too Low Diagnosis
Testing & diagnosis
From a Allmand service manual covering: M-250 Series, M-258, M-259, M-301, M-303, M-304, M-310, M-311, M-313, M-314, M-319, M-326…. Check it applies to your exact model before use.
Procedure
- Symptom: motor RPM faster than normal; cylinder will not extend; excessive turbulence in reservoir.
- Possible causes: adjusting screw backed up; foreign matter trapped between seat and ball/cone.
- Loosen jam nut and turn adjusting screw clockwise a turn or two and watch gauge; continue until required setting reached; retighten jam nut.
- If pressure does not increase, turn adjusting screw counterclockwise all the way out; energize pump to flush dirt past seat.
- Inspect cone or ball for nicks and replace if necessary; reseat with drift punch and hammer; reinstall spring and adjusting screw and reset pressure.
- If replacing cartridge relief valve, push blunt object into nose to push poppet after backing screw out; blow compressed air through side port.
- If procedure fails, check for worn pump or leaking cylinder.
Tools required
- Pressure gauge Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Source: Allmand service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.