Grillmeister
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Good morning,
Reference
1984 ONAN 4.0 Generator
Model #4.0 BFA-1R/16004C
Serial # B843751185-E
I am chasing an intermittent shut down of my 1984 Onan 4.0 generator it runs perfect but now while stationery (not driving) under load or not it will intermittently shut down after 30 minutes to 2 and 1/2 hours, but will re-start immediatly everytime. I changed the fuel filter, and oil pressure switch, but it did not help. The next thing I can think of is possibly a bad thermal switch but I don't know where it is located. I realize a 25 year old generator could have almost anything cause this. I was just hoping to change a few simple things for an experiment and get lucky. I have had this unit for six years and so far it has been pretty much bullet proof.
Thanks for any suggestions, Gary
Solution posted below
Thanks, Gary
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edited 11/03/08 10:18am by Grillmeister *
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MAJESTYPOINTERS
MONROE, MI.
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Joined: 04/08/2008
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I had a problem with mine shutting down at one time.
There is also a "thermal" shut off switch on onan gens.
My gen set had a mouse build a nest in the cooling housing.
It stopped the air flow over the cyl. head cooling fins and would cause the head to over heat and shut down after a short run time.
I cleaned out the cooling fins and the problem whent away.
Just one other thing you can check before you start replacing parts.
One other thing.
You can jump your oil pressure switch to test if it is why your gen shuts down but you should "wet test" your oil pressuer with an actual gauge first to make shure you do not harm the engine.
* This post was
edited 08/14/08 08:54am by MAJESTYPOINTERS *
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gunny357
North Carolina
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Get the one from Onan, it will be the correct one in regards to the pressure at which it switches, it'll fit too.
Oil pressure should be at least 30 psi running at rated speed. Switch should be closed (completes circuit) with less than normal oil pressure.
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Grillmeister
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MAJESTYPOINTERS
Yes, I did jump the pressure switch and the suggestion to "wet" test the pressure with a gauge is a very good one. It is kind of tough though considering how long between shutdowns. I tried this with a volt meter on the pressure switch and I ran out of beer before anything happened
Thanks for the help, I will try to find the thermal switch.
gunny
Thanks for the reply, I did get the ONAN factory oil pressure switch part #309-0322 from my local ONAN service center. Unfortunately that was not the fix, it shut down after 2 ½ hours of experimenting. I guess I need the next round of ideas of what to try next. The nice part is I can live with it and continue to experiment. The only drawback is when it shuts down under load I believe this is detrimental to some of the electrical components.
Thanks for the help.
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dougrainer
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IF you have the old style Point and Condensor ignition system---replace the condensor. There is NO thermal switch on your model BFA. Doug
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TEXAS
Centerville Tx
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Joined: 08/17/2003
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First of all. Always have plenty of BEER on hand before you begin any test. The condensor was a problem at on time. Onan had a PSB out on it. I think if it has a black top on it it is the bad one. I have the PSB list will check it out.
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Grillmeister
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Thanks for the replies, I am lucky I do not have a Point and Condenser ignition system. I had to figure that out when I did a tune up. I have the electronic replacement that I am told NOT to mess with. It is good to know I don't have a thermal switch so I can rule that out. I think my next move before I take it to the ONAN service center will be to run a can of Sea Foam through it and see what happens.
Time to stock up on BEER
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TEXAS
Centerville Tx
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OK So yours has been converted. That's good one less thing to worry about. You have no safties except low oil preassure. I would look for the simple things. Lose connections,cracked fuel lines,whatever you canb think of.Just have Plenty of BEER.
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ssands
Nerk, Ahia
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Joined: 06/04/2004
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My problem was the fuel pump. It would run for a while and stop pumping. Next time it stops, disconnect the fuel line after the pump then try to start it again to make sure you're getting fuel. I doubt this is your problem as yours will re-start immediately. I would hope I would not have to caution you about being careful with the fuel. Good luck. Ended up taking mine to the local Onan service center. They were very good. I tried swapping parts but all I ended up with is a stash of spare parts.
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dougrainer
Carrolton
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He stated that it restarts immediately. If the fuel pump was the problem, it would have to crank five to ten seconds to get the pump to fill up the Carb bowl. I would also lean towards the Armature brushes and how clean the Armature area is (No Dirt buildup). Also, I would remove the Carb and verify it is clean inside. You would be amazed how much crude can be in the Carb and bowl/jets. Doug
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