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Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 13581
Experience:  have worked on and around most engine models for 35 yrs./Polaris ATV expert
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I have a onan 5.5 hgjad-2558b generator I have a code 31 for

Customer Question

I have a onan 5.5 hgjad-2558b generator I have a code 31 for overspeed the unit runs a while then smells like engine gets hot after 20mins with air filter out like its has blowby I took compression and has 160psi at both cylinders I even checked fuel pressure has 43psi,runs ok but after awhile it dies and wont start cleared code and comes back soon as starts after cool we don't use the gen part only for the boom this on a versalift boom truck,where should I go from here thanks

Submitted: 2 years ago.
Category: Small Engine
Expert:  Hank F. replied 2 years ago.

My name is ***** ***** I am going to assist you with this.

First, have you checked to make certain there is plenty of free air for the cooling system, as well as an unobstructed exhaust? Both the intake and exhaust on this unit are underneath, and must be kept isolated.

When the unit shuts down, have you checked to see if you are getting spark to the plugs while it wouldn't start?

Have you checked to see if the fuel pump is pumping fuel after the unit shuts down?

Connect a frequency meter to the unit, and start it up.

Monitor the frequency reading until the genset shuts down.

What readings do you get?