B&S 10J902 won’t keep running

LKB

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Greetings:

I have a Troy Bilt pressure washer that has a B&S 4.5 HP vertical shaft engine (appears to be 10J902 or close to it). Recently, the engine developed the following problem: it’ll start and run a few seconds on the gas from priming it with the bulb, but won’t run at all thereafter. (Same thing with starter fluid.)

Tried cleaning the carb; no luck.

Completely replaced the carb and cleaned out the gas tank (the carb bowl is molded to the top of the gas tank). After I did that, it fired up and I figured, “problem solved.” Next day, I gassed it up to begin a spring cleaning — same old story. Removed the carb and checked/re-cleaned the screens, bowl, etc. Based on an online tip, I scored the mating plate at a place where there’s too long a distance between the bolts to create a reliable seal on the diaphragm (apparently this is a design flaw for this type of engine, and scoring the plate at that location is the official B&S fix for it).

Put it back together, and after a few tries managed to get it running (enough to run through an entire tank of gas).

This morning, gassed it up to finish the project: back to square 1; same old story. It’ll start and run until the gas from the prime is exhausted, then it dies. If I push the priming bulb when it starts to die, it’ll run for another second.

Ergo, for some reason it’s not sucking gas from the tank. Another data point: the priming bulb takes a few seconds to return to shape after depressing it (In the past, it would spring back almost instantly). I’ve blasted out everything in the carb repeatedly, so it doesn’t appear that a jet is clogged (but with these molded plastic carb bodies it’s admittedly hard to tell).

Ideas on how to fix?
 

bertsmobile1

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If the primer is slow returning then there is a blockage
The pick up tube has a filter on the end of it which gets clagged up
Other than this new diaphragms are in order .
Be wary of NOS ones as they can be quite hard from age I have sent more than one back
Because they are getting on, the shelf stock can be very old
 

sgkent

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I have a similar engine on a Craftsman Pressure washer. On mine it is labeled Quattro 4.5 HP. Same air filter housing and carb as yours. I think Generac made it. Here is what I did to get mine running at 100%

Replaced the head gasket. The head comes loose over time. At least re-torque it to spec.

Did a compression test on it after that, and it only had 38 PSI. Adjusted the valves and that came up to 70 PSI. That is within spec for my engine. Valve guides are worn on mine from all the hours but it still runs well.

Replaced the carburetor with a B&S original, correct number.

Filed the top of the fuel tank level as they can warp. Some shops use wet and dry sand paper on a piece of glass. I was a machinist for some time by trade so using a file to do that was quicker and no need to clean the tank afterwards other than compressed air. Don't use a file unless really good at it because one small slip or getting the angle wrong can ruin the tank.

The fact your primer does not return likely means there is some kind of blockage like at the screen like Bert said.

When replacing the carb, make sure the gaskets go in the correct order. Do not over-tighten

Did a standard tune up, plug, oil, new air filter (I found that my engine ran better after taking the old air filter off even though it wasn't all that old. New filter solved that. I also set the air gap because I removed the coil but that is not needed.

Use canned fuel, the washer just runs better with it. Starts easy and has no surge or stumble going from slow speed to high speed or when the wand is pulled. Starts like when it was new.

 

bertsmobile1

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TRS does very informative posts and are really worth the pain of watching
If you don't understand what is going on after atching any of them then get some one else to fix your gear.
Just unfortunate that is voice puts me to sleep .
 

sgkent

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TRS does very informative posts and are really worth the pain of watching
If you don't understand what is going on after atching any of them then get some one else to fix your gear.
Just unfortunate that is voice puts me to sleep .
it does the same to me. I had to break it up into 3 viewings to get thru it the first time, but the guy is dead on. reminds me of a math teacher I had once in 10th grade, Mr Warner. Sort of ironic too, my grandmom was a Warner. :)
 

LKB

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it does the same to me. I had to break it up into 3 viewings to get thru it the first time, but the guy is dead on. reminds me of a math teacher I had once in 10th grade, Mr Warner. Sort of ironic too, my grandmom was a Warner. :)
Thanks to all. The video is excellent as it ID’s exactly what’s what.
WRT the admonition to use a OEM carb, any idea where to get them? I can find plenty of aftermarket ones, but places that source B&S parts list the carb as “discontinued.”
 

bertsmobile1

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Get one from Rotary, Stens,Prime Line or Oregon.
Chances are they are the same carb from the same factory but these ones usually have has some sort of QC applied to them and of course come with a real guarantee .
A lot of the stuff from vendors who use platforms like Ebay & Amazon are actually defective parts bought as scrap metal then on sold as "OEM" or "fits a ..." in the knowledge that 90% of the people who get a dud will just chalk it up to experience, & buy another from some one else
 

LKB

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FYI, ordered a $15 tune up kit from Amazon (new carb, gaskets, diaphragm, o-rings, air filter, spark plug, governor springs). Took less than 10 minutes to install; machine fired right up.

Part of me enjoys being able to diagnose and fix the problem. Another part recognizes the money value of time. When it comes to debugging small engine carbs (especially for those of us in areas where ethanol-free gas is unobtainium, and thus crud in the fuel system is a fact of life for outdoor tool engines), I’m coming to the conclusion that if a quick cleaning doesn’t work and you can just pop a replacement carb on the machine for $10-15, it’s most efficient to just treat the carb as a consumable.
 

slomo

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it’ll start and run a few seconds on the gas from priming it with the bulb, but won’t run at all thereafter. (Same thing with starter fluid.)
Fuel delivery issue. Look at the main and the pilot if you have one. Something is clogged, engine starving for fuel.
Tried cleaning the carb; no luck.
Describe your cleaning method entirely.
Did a compression test on it after that, and it only had 38 PSI. Adjusted the valves and that came up to 70 PSI.
Did you use a car type gauge or one for small engines?

Remove the gas cap. See if it runs the tank dry. If so get a new cap or drill a tiny hole to vent the cap.
 
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