# Need help diagnosing problem



## BrianWV (Nov 12, 2008)

I have a 74 model sears suburban series 16.5 horse with an Onan engine. Over the past couple years I have had to run it with the choke pulled partly out. Each year a little more.
This year, it will start , but will not pull itself.
There is blowby coming out of the dipstick, but the engine does not smoke at all.
I hate to trash this thing, but I don't know where to start with working on it.
Are parts still available? The carb has been rebuilt twice.
Any suggestions?


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## wyomedic (Nov 12, 2008)

If it were me, I would replace the spark plug and then see if any differance. Still the same, I would look into the carb. Choke sticking? Maybe fuel filter? Bad gas? Just some suggestions. Good luck!


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## Bill Kapaun (May 8, 2007)

Sounds like the engine is getting "tired"!

Check for vacuum leaks in the carb/ntake system.
Worn throttle shaft, leaky gaskets, loose bolts kind of things.
A restricted fuel filter could also contribute.


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## BrianWV (Nov 12, 2008)

fuel and plugs have been ruled out. I was told the at some point the heads should have been removed and the valves adjusted, this has never been done. 
I would think if the rings are bad, it would smoke.
Would the valves being out of adjustment cause enough compression loss? I am not at all familiar with Onan engines. I do know they are hard to find parts for and no one around here will work on them.


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## 2COR517 (Oct 28, 2008)

I have a Kohler on a GT 6000 that did about the same. I ended up dumping all the fuel, including the lines and bowl. The bowl is very important to empty. Put it all back together and the carb was way out of adjustment. The idle stop/speed and idle mixture both needed to be adjusted. I think there was a full throttle mixture screw also. After the adjustments it ran great. As for the valve adjustment, I don't know. I've only had a few briggs open, which were not adjustable. If the adjustment is needed to compensate for worn cam lobes, I believe you would need longer lifters.


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## HYDROGUARDIAN16 (Feb 14, 2007)

yeah you may be looking into a good amount of money to get parts for your engine. Try starting off with a carburetor overhaul kit. It includes new gaskets, jet, needles, float needle, float bowl gasket, and some new throttle plates. Plus a bunch of other goodies to replace in the carb. They run around $25 for briggs, I am not sure though what onan would charge for a rebuild kit. But its best you seat any jets or needles and count the amount of turns. Once you seat the new needles or w/e back it out the amount of turns it took you to seet the needle. When doing this DO NOT tighten the screws(needle), just turn until it gently stops. There will be small smartie candy sized metal pieces, use a punch to take them out carefully, then use some carb cleaner to clean the internals out. Once cleaned install the new piece with the punch ( hit the center of the small circle shaped piece) and once it is in place, use some nail polish to seal the piece in. There you have it. Be carefull, carb cleaner can ruin rubber.

Happy fixin

Ben


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## HYDROGUARDIAN16 (Feb 14, 2007)

sounds like your fuel to air mixture isnt right or it simply is not getting enough fuel.


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## Jetblack1525 (Nov 9, 2008)

maybey its not getting enough fuel. that might cause it to not pull itself. once a load is put on it it just stalls out, just saying though. by the way, what year is it?


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## BrianWV (Nov 12, 2008)

it's a 1974 model with an Onan engine.


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