1978 Johnson 4HP outboards Service Manual, Page 20Get this manual
TROUBLE ISOLATION CHART PROBLEM: STEP ENGINE MALFUNCTION DUE TO FUEL SYSTEM PROCEDURE RESULT
Fuel OKGo to step 2Check Fuel Supply Is there fuel in tank? Is the fuel mixture correct? Is the fuel fresh? Is the fuel tank clean inside? Fuel questionableDrain and fill tank with correct mixtureSee page 2-683146
Fuel tank dirtyClean fuel tankpage 3-12
1No fuel or old fuelwrong mixture 2Blocked pick-up screen 3Dirt, varnish, water
Filter screen cleanGo to step 3Check Fuel Filter Remove fi Iter cover and inspect screen for dirt and varnishInspect gasketScreen dirtyClean or replacepage 3-11Gasket OKGo to step 3ReplaceSee