Johnson 9.9 Starting Prob. Trouble shooting/ Fuel Pump Repair $3.99
I recently purchased a 1974 Johnson 9.9 hp motor and could not get it
Started , so here is how I found problem and repair.
1. First clue was that after pumping fuel line bulb many times could not
get it to hard state.
2. Removed upper spark plug and put a small amount of gas in hole and
replaced plug.
3. Motor started right up but would not keep running.
4. Repeated step 2 and after motor started I kept pumping the fuel bulb
and motor keep running as long as I pumped the bulb.
5. Took filter off at fuel pump and verified that filter was not plugged
and that gas came out when I pumped fuel bulb.
6. Removed fuel pump and scribed a line across the 4 sections so I could
put it back together properly.
7. I carefully took fuel pump apart and noted position of small and large
springs and their associated plastic end caps.
8. In my case the main fuel pump diaphragm (which is nearest to motor)
had a small tear in one corner.
9. I went to AutoZone parts store and found an auto carb. Accelerator
pump that had diaphragm very similar to original diaphragm.
AutoZone part no. 90082 and cost $3.99.
10. The Accelerator diaphragm had 2 metal plates swedged together in
Center. I drilled out the swedged area and removed the plates and
was left with a nice diaphragm I could use to repair my fuel pump.
The only problem is there is a small hole in center.
11. Cut a 3/8? square piece from a thin latex gardening glove and use a
Exacto knife to cut a small hole in center for snug fit for a 4 x 40 screw.
12. Take the large spring plastic end cap and drill and tap in center for
a 4 x 40 screw.
13. Install the threaded end of a nylon 4 x 40 screw through latex washer,
then through the center hole of new diaphragm (note the beveled side
of the diaphragm should face toward fuel pump end plate) into the
threaded hole in the plastic end cap. See attached sketch.
14. Tighten the screw until you squeeze the diaphragm between the latex
Washer and the plastic end cap. Firmly tighten the screw but not to
tight, you don?t want to damage the diaphragm.
15. Cut off the excess nylon screw threads protruding through the plastic
end plate.
16. Reassemble the fuel pump, install on motor and you should have a
nice working fuel pump. Try squeezing the fuel bulb a few times
and it should get very hard, indicating that things are working
correctly inside the fuel pump.
I recently purchased a 1974 Johnson 9.9 hp motor and could not get it
Started , so here is how I found problem and repair.
1. First clue was that after pumping fuel line bulb many times could not
get it to hard state.
2. Removed upper spark plug and put a small amount of gas in hole and
replaced plug.
3. Motor started right up but would not keep running.
4. Repeated step 2 and after motor started I kept pumping the fuel bulb
and motor keep running as long as I pumped the bulb.
5. Took filter off at fuel pump and verified that filter was not plugged
and that gas came out when I pumped fuel bulb.
6. Removed fuel pump and scribed a line across the 4 sections so I could
put it back together properly.
7. I carefully took fuel pump apart and noted position of small and large
springs and their associated plastic end caps.
8. In my case the main fuel pump diaphragm (which is nearest to motor)
had a small tear in one corner.
9. I went to AutoZone parts store and found an auto carb. Accelerator
pump that had diaphragm very similar to original diaphragm.
AutoZone part no. 90082 and cost $3.99.
10. The Accelerator diaphragm had 2 metal plates swedged together in
Center. I drilled out the swedged area and removed the plates and
was left with a nice diaphragm I could use to repair my fuel pump.
The only problem is there is a small hole in center.
11. Cut a 3/8? square piece from a thin latex gardening glove and use a
Exacto knife to cut a small hole in center for snug fit for a 4 x 40 screw.
12. Take the large spring plastic end cap and drill and tap in center for
a 4 x 40 screw.
13. Install the threaded end of a nylon 4 x 40 screw through latex washer,
then through the center hole of new diaphragm (note the beveled side
of the diaphragm should face toward fuel pump end plate) into the
threaded hole in the plastic end cap. See attached sketch.
14. Tighten the screw until you squeeze the diaphragm between the latex
Washer and the plastic end cap. Firmly tighten the screw but not to
tight, you don?t want to damage the diaphragm.
15. Cut off the excess nylon screw threads protruding through the plastic
end plate.
16. Reassemble the fuel pump, install on motor and you should have a
nice working fuel pump. Try squeezing the fuel bulb a few times
and it should get very hard, indicating that things are working
correctly inside the fuel pump.
