1998 Johnson Evinrude "EC" 9.9 thru 30 HP 2-Cylinder Outboards Service Manual, Page 70Get this manual
Disassembly
1Remove primer pump housing retaining ring from primer pump2Remove primer plunger from housingDiscard O-rings
Inspection
1Inspect brass plunger shaft for any burrs or scratchesRemove small scratches by polishing the plunger with crocus clothIf the plunger has deep scratches, replace the plunger
2Inspect plunger where cross hole intersects inside holeAny burrs around cross hole will accelerate wear of O-ringsRemove any protruding burrs and polish with crocus cloth
The check valve under the small nipple on the primer pump housing allows fuel flow out of the pump housing and prevents flow into the housing