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Discussion Starter · #1 ·
Greetings:

I have a Troy Bilt pressure washer that has a B&S 4.5 HP vertical 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).

Ideas on how to fix?
 

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The bulb is either the engine choke or purge bulb they are both different.
B&S 4 stroke with gravity fuel tank above the carb fitted with a plastiic top and a large diaphragm and choke primer bulb you press 3 times to start the engine are very reliable. If the choke bulb does not return immediately it suggests a vacum in the fuel tank which will stop the engine from running correctly check the fuel cap most are fitted with a valve to allow air into the tank. Purge bulbs on small engines have a totally different operation they suck fuel from the fuel tank and the fuel tank can be lower than the carb, you are filling the carb with fuel to start the engine and this puts fuel into the engine via the main jet hence a rquired amount of pumps to purge the system. A purge bulb is more important than a primier bulb that is only a choke mechanism you can see squirting fuel into the carb to start the engine. A purge bulb is part of the fuel delivery system returning fuel to the tank so the engine does not over fuel and an important part of the system for the engine to keep running. You need to understand the difference choke primer bulbs are fitted to 4 stroke engines with carb fuel chambers. Purge bulbs are fitted to carbs with no fuel chamber to purge air from the fuel system and have non return valves so the carb always has fuel to run in any position needed like chainsaws/strimmers/weed wackers/blowers etc. Engines with purge bulbs retain a vacum in the fuel tank to assist fuel delivery to the carb and stop fuel leaking from the tank, primer choke bulb carbs rely on no vacum in the tank and normally fitted on machines always in the upright position like lawn mowers/chippers/water pumps etc. 2 stroke engines with purge bulb carbs rely on a crankcase vacum for engine lubrication and correct air fuel mixture with no engine valves to ajust. 4 stroke engines need engine oil for lubrication and no crank case pressure but need inlet/exhaust valve adjustment. I hope this helps understand the two different types of fuel systems.
 
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