Toro 3521 runs for 30-40 seconds, stalls out. Fuel/carb issue? - Snowblower Forum : Snow Blower Forums
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post #1 of 12 Old 06-02-2015, 10:24 PM Thread Starter
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Toro 3521 runs for 30-40 seconds, stalls out. Fuel/carb issue?

Toro 3521 model 38035, serial no 9000135 (1989), with a Tecumseh H35-45598T.

I had a similar issue last year when I first got it, but thought I had it solved. This past winter I ended up having to restart the engine after each pass down my driveway.. extremely irritating to say the least! But it was too cold to bother looking at it.

The past few days I took the engine off, greased everything up and repainted the chassis. I cleaned the carbs out, cleaned some carbon buildup off the valves and piston head and put it all back together.

It runs great, for about 30 seconds or so and then it sputters out like it ran out of gas. I've tried a few things, adjusting the power/idle mix screws, made sure it has fresh gasoline, etc.. The fuel gets to the bowl, but my guess is the engine is using the fuel faster than the gas tank can replenish the carb bowl. It uses it all up, stalls, and by the time I can restart it the bowl has refilled.

I checked the float, it seems fine - it's moving freely and the little metal thing that blocks the gas inlet seems to be fine - nothing is stuck. I made sure the deeper part of the bowl is in the right place (under the part of the float that comes down).

To test my theory out, I ran it until it stalled out - as soon as it stalled out I quickly shut the fuel tap off so no new gas could flow. I opened the carb bowl up and there was very little gas in there - I'd expect it to be relatively full.

I think I've narrowed the problem down, but I just don't know what to do next? I'm not sure if it's the fuel not getting to the bowl, or the engine using the fuel up too quickly? How can I adjust how fast the fuel gets into the bowl? When I had the bowl open, I opened the fuel tap and the gas definitely flows in, but it's a steady trickle..not sure if that's fast enough? I don't have anything to compare to.

Any suggestions are appreciated!
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post #2 of 12 Old 06-02-2015, 10:33 PM
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remove the gas cap and try it again, check for obstructed fuel lines. if its not one of those then check your ignition
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post #3 of 12 Old 06-02-2015, 10:35 PM Thread Starter
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Thanks for the response, I should have noted:

I checked the gas cap, the vent is unobstructed and completely clear - but to double check I ran it with the gas cap off and no difference.

I also checked the fuel line, it doesn't have any obstructions - it looks like the previous owner replaced it around 2006 (the hose is stamped with that date, anyway).

When you say check the ignition, what can I check on that exactly?
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post #4 of 12 Old 06-02-2015, 11:06 PM
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Is there a filter screen in the outlet in the bottom of the gas tank? I'm not 100% sure but I'm betting on fuel delivery problems.

Joe

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post #5 of 12 Old 06-03-2015, 05:15 AM
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The fuel line could be swelled up inside too, especially true if he used something not rated for gas or if it is kinked behind the flywheel. You should be getting more than a trickle. It should be coming out pretty quick. You can try disconnecting the hose from the carb and then compare that to what comes out of the bottom of the tank with the hose removed there.

Is the tank full? Sometimes they don't run so well when the tank is near empty. The weight of the fuel will push it through the hose better. Also, the angle of the tank relative to which side of the tank the outlet is on matters.

Last thing is the hose should be running pretty straight. If it has a big drop down like a p-trap in a sink that will affect it poorly.

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post #6 of 12 Old 06-03-2015, 09:22 PM Thread Starter
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Alright, I tried a few things and think I've narrowed things down. I replaced the fuel line and hung the fuel tank above the snow blower, tried it. It ran for a solid 10 minutes with no issues. Encouraged, I ran the new fuel line behind the cylinder and put the tank back in the usual spot - it stalls out after 30 seconds as it was before.

I made sure the fuel came out of the tank at a decent rate (it comes out FAST) with and without the new hose attached. The problem seems to be the fact that the fuel line goes down from the tank and then back up into the carb. I've been testing it out with small amounts of fuel (maybe half a liter or so) so I don't need to keep filling up / emptying the tank.

Here's what I'm talking about:




I'm thinking about raising the fuel tank up about 3-4 inches - hoping that will solve the issue.
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post #7 of 12 Old 06-03-2015, 09:45 PM
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If you install a 90 degrees shut off valve right at the bottom of the tank, the hose will not have to do the curve and go too far down (and it's a safety item).
I personally would run it with a full tank of fuel and see how it runs, I think it will solve the issue as the fuel will have more pressure at the carb.
In the other hand there has to be a restriction somewhere between the tank or the carb, unless the carb float needle is sticking and not letting enough fuel come in or the elbow at the carb is partially clogged.
I think I would take the carb bowl off, have a container ready underneat the carb to collect the fuel, place the 1/2 litter of fuel in the tank and manually close an open the needle by moving the float up an down and see how much fuel you get, maybe then you would find out if fuel supply is or is not enough.
Just some thoughts.
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post #8 of 12 Old 06-05-2015, 09:22 AM
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I can't be sure but in your first pic it looks like your fuel line is partially flattened or collapsed. I don't believe that raising the level of the gas tank is going to help. There are thousands of those engines with that same tank configuration that don't have problems. Replace your fuel line with some good quality line qnd make double sure verything else is clean. As I said earlier there may be a filter screen of some type right at the bottom of the tank that is partially clogged. Let us know what you find.

Joe

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Ariens 5/22 ss ..Sold
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post #9 of 12 Old 06-05-2015, 11:14 AM Thread Starter
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michah68kj - I don't disagree, it seems strange to me since this is essentially the stock configuration. I've checked the fuel tank, there is no filter screen and the fuel flows out of the tank at a good rate. The fuel hose you see pictured is brand new fuel line from the hardware store, it's definitely not flattened or collapsed and if I pull the hose of the carbs fuel flows through it just as quickly as if I didn't have a hose on the tank.
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post #10 of 12 Old 06-05-2015, 11:28 AM
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I'd suggest you check the fuel flow at the carb by removing the float bowl, there is where you would really see the flow, manually close the fuel inlet by pushing the float up and open it by releasing the float, do this several times and see if maybe the valve is sticking, you should have very good flow there, and it should open and close as you move the float up and let it down.
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