Re: 1990 fuel priming problem
Fuel filters rarely become totally full of fuel. If that's what you are using as an indication of failure to prime, you are incorrect in that assumption. If the primer bulb firms up as you squeeze it, you have proper prime. Next, do you understand the starting procedure? 1) Prime, 2) raise fast idle lever about 1/2 3) turn key to RUN (not start), 4) Push and hold the key in for a count of 8 or 10, 5) Turn key to START. When the engine starts, lower the fast idle to a comfortable idle -- but not all the way down as the engine will likely stall. Be ready to bump the key (push it in momentarily) to give the engine another shot of fuel if it tends to die. If this is the procedure you are using, then other checks are necessary.
1) Plugs wet? Indicates no spark or simply flooded.
2) Check for spark. Kill switch activated? Set it to RUN
3) Battery fully charged?
4) Last but certainly not least is the requirement for fresh fuel.
5) Try mixing fuel/oil in a spray bottle and squirt some into the carbs while cranking. If the engine tries to run, you have a bad fuel, bad fuel pump, or dirty/clogged carb issue.
Lastly -- diagnose, isolate, then repair. Don't shotgun the problem by replacing parts that likely don't need replacing.
