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Ask Hank F. Your Own Question
Hank F.
Hank F., RV tech - emphasis on gensets
Category: RV
Satisfied Customers: 15261
Experience:  RV tech since the beginning of the millenium.
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Onan 6.5 nhm geneator starts and runs seconds then dies off

Customer Question

Hi, onan 6.5 nhm geneator starts and runs for 20 seconds then dies off governor goes to full open to try to compensate new spark plugs new coil,new ignition module and board. new propane regulator but a replacement not from onan. seams to be running out of gas. will restart, by passed fuel filter and fuel selonoid. I am out of options.
Submitted: 1 year ago.
Category: RV
Expert:  Hank F. replied 1 year ago.

Hello, my name is ***** ***** I am going to assist you wtih this.

What is the full model number of the genset, exactly as it is written on the data label?

Customer: replied 1 year ago.
6.5nhmfa26115f and FYI I own a rental store and have been working on small equipment for 40 years, compression test show 150 and good spark now with the replaced parts. The replaced regulator has a pull off pressure of -1.5 psi is this correct or should it have the lighter spring to pull of at -.5 . The regulator/ fuel supply seams to be the problem. breakers are off on the gen set so no load on the engine. We can talk on the phone it might be easier XXX XXX XXXX. Hal
Expert:  Hank F. replied 1 year ago.

Your lock off pressure is way too high. The lock off pressure should only be 0.15"WC to 0.25"WC.

Customer: replied 1 year ago.
some confusion, my understanding, this generator is a liquid line feed to the generator the impco model J regulator in the generator which reduces the tank pressure to 1.5 pounds internally in the regulator. the regulator needs a vacuum if .5 pounds to flow propane. in playing with the generator we have found that, if we restart the generator several times in a row, and it warms up it runs longer and longer ex: 30sec. then 1.5 min then 3 min then 5 min. it actually shut down after running for 5 minutes. re started again and all was fine took a load ran for 30 min.
Expert:  Hank F. replied 1 year ago.

Sorry, I didn't realize you were working on a liquid withdrawal system - you didn't mention that.

What you are describing would normally be attrributed to a stiff or contaminated diaphragm. But since your regulator is new, that should not be an issue.

Without being able to see this, I am not sure where to go next.

I will opt out of this question. Perhaps another expert will be able to assist you.