Toro 20045 lawnmower only starting and running if sprayed into carb

[jason]

My Toro 20045 started misbehaving late last summer getting harder and harder to start. After googling and watching Youtube, suggestions seemed to be to clean and/or replace carburetor. Following that advice, I carefully removed the carburetor, unscrewed the bowl and cleaned the jet holes of the bowl jet and then proceeded to clean all of the indicated holes of the carb. I did the cleaning first with shots of carb cleaner spray followed by trash can tie wires through the holes and finally used compressed air on each hole. I also checked the action of the float and value and it seemed to be moving normally. Before replacing the carb, I replaced the gaskets on each side. Once reinstalled and with several primer pushes, still no start. My mower does start first pull and keeps running only IF I remove the air filter cover, take out the air filter and spray carb cleaner or gas into the carb entrance. Then I can actually mow the grass once the filter is reinstalled but once it runs out of gas, I have to go through the process of removing the filter again to give it a shot of cleaner.

Last summer, the primer bulb had cracked to the point where it wouldn't press or release properly anymore and I replaced it. This is the type of primer/ air filter assembly the mower has:

I notice that when I have the air filter removed and press the primer, I don't see anything happening in the carb chamber. Shouldn't I be seeing squirts of fuel entering the carb when the primer is pushed? I've suspected that the no start problem may lie within this primer/ air filter assembly, but I am not sure how to test it. I sent compressed air into the short hose as seen in the image of the amazon link. What is the short hose for? Is it supposed to pull gas from the tank when the primer is pressed? When I remove this hose along with the air filter assembly, should I be seeing gas dripping from that areas of the mower. Obviously I do when removing the carb hose.

At this point, I think the problem lies in either the carb itself or the air filter/ primer assembly. Before I run out and buy one or both items, is there any way I can definitively test each item first? I wish I knew more about how the primer assembly is supposed to work also.

I spent the weekend trying to get the mower starting the way it is supposed to, but to no avail. The good news is that I got the yard mowed, but each time I would have to refill the tank with gas, I'd have to remove the air filter, spray a bit of carb cleaner into the carb, and start first pull. This won't be fun if I have to do it all summer long.

Any help would surely be appreciated.

Thanks in advance, Jason

[Stormin Mormon]

I've done a bit of small engine work, over the years. This might not be at all useful to you, but some time when engine won't start on its own, the gasket between the carb and the engine is leaking air. A bit of Permatex IIb non hardening gasket sealer closes the leak. Beware, the stuff is messy and doesn't come off hands or clothing very well. gloves, and treat it like hazardous waste.

On some engines, there is a choke plate that closes when the throttle cable is all the way forward to choke. Probably not issue, here. I'd think the primer button would make gas go into the air stream. I think?

Please let us know when it's fixed, we can learn from you.

[hrhofmann]

I agree there is something wrong in the primer area if you don't have an air leak as Stormy says. The fact that it runs ok once it is manually primed by adding gas directly says that the primer is most likely the problem.

I don't have any further advuice as I have never had to take apart any primer assembly. There should be some good advice here pretty shortly as you are not the first to have this problem.

[dpb]

On 4/28/2014 6:37 AM, jason wrote: ...

Ayup, if the primer bulb isn't pulling in gas, it's either not installed correctly or the pickup is blocked or the new one is/was defective. That's your first thing to resolve. (BTW, I _DETEST_ the switch away from a standard old choke carb, but they didn't ask me...)

[trader_4]

+1

The purpose of the prime bulb is to pump squirts of gas into the carb. If you don't see, it, sounds like the bulb isn't working. I'd disconnect the bulb line at the carb and see what happens when the bulb is pushed.

I also agree that the traditional choke was better. The biggest problem with the bulbs is they don't last, crack and then it's a PIA.

[Fat-Dumb and Happy]

Sounds like you probably need to replace this gasket on the air cleaner assembly or goop it up good with gasket sealer.

and a youtube of course... Now how does it work, or rather how is it supposed to work? Unlike most small engines that squirt some fuel into the carb, on a Briggs and Stratton of this type the primer pressurizes the bowl of a float type of carburetor pushing the fuel up into the throat of the carb. It is not uncommon for those types that are mounted on the air box to not work right due to warping of the plastic air filter back plate. If it is one of these types, the least most expensive repair is to remove the back plate and reinstall it with two gaskets. More information and disinformation..

[trader_4]

Sorry, but an air cleaner gasket could not produce the problem. An engine will run with a leaking air cleaner gasket or the air cleaner completely off the engine.

[Fat-Dumb and Happy]

On this one it does, the primer bulb is on the air cleaner and the pressure from the bulb has to go through the gasket. Don't ask me why they did it this way, probably seemed like a good idea at the time.

[makolber]

To the op After you replaced the primer last summer, did it ever start correctly after that?

When did the starting problem start relative to when you replaced the primer?

Mark

[Jason]

When I replaced the primer, it took a lot of priming to get it going...

10-20 primes I would say. It was just getting worse and worse though. I also noticed that when I removed the air filter assembly so I could change out the primer, the gasket between the air filter and carb broke in half. I didn't have another handy and just put it back together. So it's possible that I might have initially offset priming trouble by replacing the rubber bulb, but then recreated the problem when I didn't replace the gasket.

Based on replies here, I went ahead and ordered a gasket "kit" that will include gaskets for the carb bowl and jet as well as for the one between the air filter and carb. The next step will be to replace the gaskets and see what happens.

Once I start the mower first pull after spraying gas into the carb and replacing the air filter, the mower runs fine and easily cuts the lawn, so at least I have had little down time.

jason

[trader_4]

But then he should see gas spraying out of this carb primer plate. He says he doens't see gas getting to the carb when he pushes the prime bulb.

[hrhofmann]

Yeah, he needs to be able to see some raw gas when looking in to the carburetor from the removed air cleaner and pushing the primer.

[Jason]

UPDATE 5/3:

The carb gasket kit arrived two days ago and I replaced the carb to air cleaner gasket as well as the other gaskets in the carb. Still no prime. I even doubled up the carb/ air cleaner gasket, but this still didn't help. Finally, I removed the primer bulb and cleaned the screen underneath thoroughly with compressed air. Replaced the bulb and still no prime when pushed. Just to re-confirm that the carb was ok, I once again sprayed a little gas directly into the carb and the mower started right up.

I think the only thing left here is replacement of the entire air filter holder.

Jason

[trader_4]

There is still no prime because none of that has anything to do with the prime. The primer is just a bulb that pumps gas through a hose to the carb. Gas should squirt into the carb and out the end of the hose if it's disconnected, without regard to any carb gaskets.

I even doubled up the carb/ air cleaner gasket, but this still

Isn't there a gas line from the primer bulb to the carb? I asked previously, if it's disconnected and you push the bulb, do you get gas? If you get gas, then there must be an obstruction in the orifice between where the hose connects and the carb throat.

If you don't get gas, (which I suspect), then the problem is with the primer bulb, lines, ie something in that path and screwing with the carb isn't going to fix it.

[hrhofmann]

How many people have to tell you that there is something wrong with the PRIMER since you are not getting a squirt of gasoline when you push the primer bulb??!!

[Mr.E]

Somehow most of the posters think a 4-cycle B&S sprays gas by pumping the gas thru a primer bulb. It does not.

2 cycles pump gas thru the carb but 4 cycle B&S use AIR PRESSURE to force fuel up thru the jet to the throat of the carb. The backcheck pressure bleed under the welch plug is probably thoroughly crudded and needs to be rodded out and cleaned per the B&S carb repair guides.

[jason]

Can you provide me to an online resource for doing this task? I noticed one or two metal plugs were included with the carb kit and I wasn't sure of their purpose. I did not attempt to touch these when cleaning the carb. I have some version of the B&S manual for this engine, but the content seems to cover several carb versions and I find it difficult to pin down exact information.

Thanks, Jason

[Mr.E]

I read a factory service manual that a friend had- I had never seen a "How it works" in any of the online references. Might check youtube.

[trader_4]

he PRIMER since you are not getting a squirt of gasoline when you push the primer bulb??!!

This guy who seems to know what he's talking about in an engine that sounds similar to what the OP has says the primer does indeed push gas into the carb throat.

WRONG! On a Briggs and Stratton the primer pressurizes the bowl of a float type of carburetor pushing the fuel up into the throat of the carb. Without knowing the specific model I can't give any really good suggestions. It is not uncommon for those types that are mounted on the air box to not work r ight due to warping of the plastic air filter back plate. If it is one of t hese types, the least most expensive repair is to remove the back plate and reinstall it with two gaskets.

And if the primer bulb doesnt' result in a squirt of gas getting into the throat, how exactly do they enrich the fuel/air mix to get the engine started? They typically don't have manual chokes on them anymore.

[bubbacotton]

My leaf blower, weed eater, tiller and chain saw all have a primer bulb and a choke. The primer bulb gets the fuel to the carb and sprays a little fuel into the throat of the carb and the choke causes a low pressure in the throat when the when pulling the start cord. I have had the chokes butterfly not close completely because of trash between the choke butterfly and the throat of the carb or a cable that needed to be adjusted. I am not familiar with a motor that dosen't have a choke.