Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

Hi,

My recently bought (second hand) Ariens ST504 won't start anymore. It used to be really easy to start. Throttle on 50%, full choke and three pushes on the primer and it would start on one or two pulls. It was the neighbor who drove it the last time so I don't know how it acted last time it ran but the neighbor didn't mention anything until he tried to start it next time.

Anyway, now it won't start no matter what. There's fresh petrol in the tank (maybe a bit too much). I've tried having the lid off the petrol tank when starting but that didn't help. The spark plug gets oily after I tried starting a couple of times and after cleaning it I can get it to *almost* start. A few puffs of pretty black smoke and then it dies. Then, the spark plug is all oily again. I checked that there is a spark and it seems fine. Probably time for a spark plug change but it seems wierd that it died so suddenly, no? 

When pushing the primer, it sounds and smells like fuel gets through but I don't know how to check the fuel line better. I haven't starting taking the covers off to check the eninge more but I was hoping to get some pointers before doing that.

So, any ideas?

/Ola, Sweden

Ola - are you sure its oil that you are finding on the spark plug? If that were ture, you would be getting blue smoke when the engine does attempt to run. Black smoke means excess unburned fuel. Change the spark plug firstly. Now - check the oil & see if its over full, and also see if the oil smells like gas. I'm thinking that your carburetor float is stuck & the engine is becoming flooded with fuel...

Marty

All I can say about it it's that it's an oily black/dark brown residue. Not dry black like soot. Looking down throught the spark plug seat it looks pretty oily inside. It's definetly black smoke I'm getting rather then oil-burning blue.

The carburetor float being stuck would account for the engine being almost startable when it's been left alone for a time. I.e. the excess petrol should have evaporated and it should be able to function almost normally for a few revolutions before flooding the carburetor? After a couple of tries in a row I get absolutely no response from the engine. Or is this a faulty conclusion? Will a flooded engine force petrol into the oil? I checked the oil before reading your reply and it seemed quite full, but I didn't think to smell for petrol in the oil.

How do I check, and repair, a stuck carburetor float? I'm fairly handy with engines but am used to direct injection :o)

Thank you

/Ola

Ola - if the oil level is ABOVE the FULL mark, AND the oil smells strongly of fuel, I suspect a stuck float in the carb. As for fuel evaporating, if the float is stuck there is almost a constant flow of fuel, which means it will not evaporate. Did you leave old fuel in the tank during storage? The carb float could just be stuck - a few taps with a plastic screwdriver handle on the float bowl may loosen it if its gummed up. The float itself could have developed a leak which would require replacing it - to test it, place it in a container of water & submerse it. If you see bubbles then you need to replace it. Replacing the needle/seat would be a good idea too. These parts are very inexpensive & repair is simple. A spark plug & oil change are recommended, but hold off on the oil change until we know exactly what is going on here. Let us know what you find & we'll go from there...

Marty

Now I got the engine started but not running well.

I took apart the carburetor and the float didn't seem stuck. Very clean inside the bowl and the needle was moving freely. Maybe I loosened something taking the carburetor apart or maybe that was never the problem. The float was empty when I got it out and there were no bubbles when I submesed it in water.

Putting it al together, the engine now starts with lowest setting on the throttle and 0-25% choke. It runs with an unsteady idle for about a minute and then dies. If I try to give it any more gas than idle, it dies immediately. After running, there's some soot on the spark plug. Not the oily substance it used to be but too much soot to be good. I'm guessing taking the carburetor apart messed upp some setting. Also not being able to handle any more than idle is a sign of a poor spark, no? Kind of drowning the spark as soon as more petrol is introduced.

So, now I need to get a new spark plug, just in case the spark has become weak and adjust the carburetor. Any pointers for adjusting this carburetor?

Also, on the screw that holds the bowl, there is a tiny hole and in the grooves, there is a matching hole. What are these for and must they align? Now they don't becaus when I had the screw tightened to where they aligned, the bowl leaked petrol so I had to tighten it more but could not get an entire turn more so the holes aligned again.

Thank you for your help so far.

/Ola

One more thing. I checked the oil and it was about half-filled but had a distinct smell of petrol. Not very much but enough to be noticed. Maybe there was not very much oil in there to begin with and that's why it isn't over-filled if any petrol has been forced into it.

I'm going to change the oil regardless because it has not been done this season and I don't know how long the previous owner has run on this oil.

Got a new spark plug. They didn't have Champion's so I got the NRK replacement. No difference in behavior, more difficult to start with the new spark plug and dies after about the same time. Now my arm is too tired to get it started again :o)

The NRK spark plug has a smaller gap, 0.60 mm than the Champion's 0.75 mm. Should I open the gap slightly on the new plug or leave it as it is?

Ola - I'm thinking that you loosened up a stuck float condition. Now, you have just the opposite problem - I believe your carb is running lean! If you have adjusting screws for hi & lo speeds, turn each one counter clockwise a 1/2 turn & see if that helps. If not, remove the bowl bolt. Those small holes in the bowl bolt are what meter the fuel & are probably clogged. Run a small, thin wire thru them & spray them good with carb cleaner. Put the bolt back & attempt a restart. If the engine now runs rich again, turn each screw clockwise (to their original positions) to lean it out. You're getting close! DEFINITELY change that oil!

Marty

Now I'm at a loss.

Today, I get no spark. Tried both the new and the old spark plug and nothing. So I checked with a "spark checker", whatever those are called. The kind of lamp you connect between the spark plug and the spark plug wire. I tried it before and it worked but today I get nothing from it.

I checked for electrical connections and got a bit confused:

The black wire that comes out from under the pull-start cover and that connects to the black lead to the ignition switch is always grounded. Should it really be like that? I thought setting the ignition to "off" grounded that wire by connecting it to ground via the red lead from the ignition switch. I.e. ignition off = black wire from under the cover, via the black wire to the ignition and then to ground via the red wire. Turning the key breaks the grounding via the red wire and the engine can start. Am I wrong here?

If I'm right, what do I do about this? Sounds like  it's time to take it to a professional because new electrical parts isn't readily available here. Also, since everything is under three layers of cover, I don't even know where the coil and magneto is located on this engine. Or maybe it's just a case of corrosion and I should try to repair it myself. If so, what are the steps I should take?

This thing is really haunted... Now it seems like I've managed to break my spark test lamp. So there *may* a spark. However, I can see no spark from the spark plug when I take it out, ground the tip against the engine top and then pull the starter cord. Maybe it's a so much fainter spark than the one from a car that it can't be seen with the naked eye.

Should I be able to see a spark when grounding the tip of the spark plug and pull the start cord?

Should the wire coming out from under the start cord be grounded all the time?