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Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 15198
Experience:  Certified on Onan and Generac generators
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I have an onan 4000 it turns over good. fuel pump doesnt run

Customer Question

i have an onan 4000 it turns over good . fuel pump doesnt run and it has no spark! I can jump the fuel pump and it will run!
Submitted: 1 year ago.
Category: Small Engine
Expert:  Hank F. replied 1 year ago.

What is the model number?

Customer: replied 1 year ago.
s/n co20344172 p/n 4kyfa26100k 33-3 amps
Expert:  Hank F. replied 1 year ago.

You said that the unit is not getting any spark.

But you also said if you jump the fuel pump the unit will run.

If it is not getting any spark, it can't run.

Which is it?

Customer: replied 1 year ago.
i said the pump will run if i jump it! i wanted to eleminate the pump the generator will not run !when i try to start it ther is no spark or fuel
Expert:  Hank F. replied 1 year ago.

Oh - you made it sound like the genset would run if you jumped the fuel pump.

Remove the front access cover from the genset.

Inside, in the front left corner, you will see a black 8-pin connector. Unplug it.

See if the genset will start with that plug disconnected. You will need to use the start switch on the genset itself, as that plug will disable the remote switch.

Expert:  Hank F. replied 1 year ago.

Did the genset start with that plug disconnected?

Customer: replied 1 year ago.
no it didnt
Expert:  Hank F. replied 1 year ago.


Remove the control panel from the front of the genset.

Inside, go to the coil.

Remove the small white wire from the coil, and remove the spark plug wire from the spark plug.

Set your meter to ohms.

Place one meter lead to the tab on the coil that you removed the white wire from.

Touch the other lead to the screw holding the small black wire that comes off the coil.

It should read 0.5 ohms.

Now place one meter lead into the spark plug wire, and the other lead to that same screw.

It should read 1,100 ohms.

If either reading are out of spec, the coil is bad.

Now set the meter to VAC.

Connect one lead to the small white wire you removed from the coil.

Touch the other lead to a clean engine ground.

Press and hold the start button for 5 or 6 seconds.

At cranking speed, you should see between 15 and 50 VAC.

If you do not, the magneto is bad.