Have you smoke tested the intake, or sprayed around it with flammables to check for vacuum leaks? Run a compression test as a sanity check since it started running rough?
Onan should be the name of a dog: Rough Ruff...
- Thread starter Seeburg220
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I did about 2 years ago. I took it apart last week and blew it all out with compressed air and to inspect it.
I have not. I'm going to buy a compression gauge tomorrow. Will try the ether spray on the intake, too. Thanks.
I installed the Gary Bovee Pertronix kit on my supposedly factory reconditioned Onan back in 2017 and have not had issue #1 with it since. I got this Onan from Steve Ferguson, who obtained it from Kerry Tandy after he had his replaced and had the one he took out "reconditioned". It had some kind of Onan electronic ignition on it, in place of the points, that would work for a while, then quit. It was frustrating to have to go over the whole set-up every time it quit, only to have it run for a while, then quit again.
Once I put the Pertronix on it and replaced the fuel pump with a factory style Facet, it has been rock solid dependable.
Once I put the Pertronix on it and replaced the fuel pump with a factory style Facet, it has been rock solid dependable.
I ran a compression test. Both cylinders at 100 psi. I started it and fiddled with the idle mixture screw (the one on the bottom of the float bowl). I leaned it out a little and it seemed to run somewhat smoother. 5 minutes later, without warning, it just shut down. No sputtering or backfiring, just off, like you hit the stop button. I removed the top row of wires on the board (that go to the remote start switch) and no change: it won't start. ($%^$#%!!!).
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Jump pin 9 to 5 on the control board and the fuel pump should run, and there should be spark for it to run after you hit the Start button. That way you can diagnose it. First check to see it's getting fuel. (you need at least 1/3 fuel level in your tanks for this to run btw) Then check to see if you have spark.
If you have fuel and spark, then maybe the low oil pressure switch is killing the engine? Maybe defective? That's easy to check at the control board as well.
I jumped 5 to 9 and the fuel pump is working. I am getting spark. Where I'm at now is, the float level. The book shows to adjust the float to 1/16" from the gasket to the float. Mine was way off, more like 1/4". However, when I adjusted it closer to 1/16", it flooded the carb big time. I'm wondering if that is a misprint in the manual, 1/16" ? So, what's a decent float level setting from experience?
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Was the engine running?
Mine leaked after putting on a healthy fuel pump also. It was brought to my attention that the float may seal as the engine runs, I guess the vibrations help work it into place.
What pressure is your pump putting out?
No, it will no longer start. Super frustrating, this Onan. You piqued my interest with the fuel pump pressure question. The literature says 4.5-5 psi. and roughly half a gallon a minute. Sounds a tad much, doesn't it? : )
You want the 1-4 psi. Higher pressure pumps will push the needle off the seat and make it run rich. The GPM rating is meaningless.
The heat on top of the engine will cause the dielectric material in the condenser to dry out and lose capacitance over time. Especially on cheap Chinese condensers. The condenser forms a resonant circuit with the primary winding of the coil and is fundamental to pushing the magnetic field’s energy toward the secondary to make the spark. Get a real Cummins condenser. Number of running hours doesn’t mean as much in “wearing out” a condenser as its environmental heat exposure.
When my Onan started to play up this spring and finally wouldn't start/run i looked at the carb, board, relays etc before running a jumper from the battery directly. Started right away and ran smoothly again. Cleaned the battery terminals and now running and doesn't miss a beat.
The GMCMI parts interchange shows a Napa 610-1074 pump with an advertised psi of 4-5.5
It also shows the Onan 149-0650 has been superseded with a 149-1304 that also has a psi of 4.5.5 and looks like the same pump for sale on gmcrvparts. Same for the Facet 480545 that is listed. If that were too much psi, wouldn't everyone be having problems with flooding?
I do not have time to look at what part #’s are what. But Jim Miller is 1st. The most expert available on the onans.
And 2- i thought it was very common knowledge that the onan needs the replacement pump of 1-4 psi. Much less then the pumps people feed the quadrajet with.
I ran a mr. Gasket 42s. That was 2-3.5 psi on my old onan.
Use whatever pump you want but I can tell you - from firsthand experience - that a 4+ PSI pump caused two different Onans of mine to flood. When I installed 1-4 PSI pumps the units ran great with no other changes. Just because Onan superseded a part does not mean that the new part is exactly the same; the bean counters might have triumphed over the engineers in their zeal to cut parts inventories and get themselves an attaboy. Perhaps the 4+ pump works fine on other carbs that used to use the 1 PSI pump. Who knows? I put on what the Onan engineers originally asked for and had no further problems with flooding. YMMV
Fair enough. My point was, the parts interchange has made this confusing and I'm wondering if maybe those specific listings should be removed or annotated at least. I will search for a lower fuel pump. Thanks.
Maybe it's common knowledge, but I had never heard that. I figured the part #'s listed in the GMCMI parts exchange would be correct. Perhaps not. Thanks.
Guys, don't take me wrong, I am not dissing the parts exchange list in any way - it is an incredibly valuable resource and I have used it extensively in maintaining my 1977 Eleganza. It is possible - albeit unlikely - that I have the only two Onan NH's still in existence that didn't like the 4+ PSI pumps. All I am saying is that I have firsthand negative experience with those pumps and although I am engineer myself, I understand that the guys that spec'ed a 1-4 PSI pump did that for a reason. While I acknowledge that the "engineers" from the Harvard MBA School of Engineering seem to always triumph in getting their way over real engineers, I try to use what was originally specified for a given application. Those old timers knew far more than I do about why they specified what they specified.
If you stick an 8000 PSI hydraulic pump in as a fuel pump on your onan and it works then good for you! Enjoy it! The irritating part to me is that a lot of people badmouth the Onan without taking the time to understand it - it is a tried and true 80+ year old engine design after all. It is dirt simple to fix and maintain if people would just take some time to learn about it instead of jumping on the 'net and becoming a keyboard warrior.
Mr Gasket 42s is what I used for about 5 years until it quit on me. It's about as inexpensive and common as they come. Jon hit the nail on the head.
