Stihl MS210 Start Problem

[bill18163]

I've got a Stihl MS 210 chain saw that I can't start. I squirted a little fuel into the combustion chamber, and it runs well and then stops so I'm assuming the spark plug and electrical system is OK. It's not getting any fuel. If you pull the starter cord many times and then take the plug out, the plug is dry, and the chamber is dry. I tried a new carb that I had and there was no difference. I checked all the hoses, vent and suction hose with filter attached. The filter is new. The only hose I couldn't confirm is that hose from the engine crank case to the carb because it is down under everything. I think it is called a pulse hose. So, I removed everything so I could get at that hose. Was it attached to the nipple to the carb when I disassembled everything? I don't know. Everything is so tight down there, who knows, maybe it wasn't connected to the nipple. The hose looked OK. I am going to assume it was. What would you look for next?

[bgsengine]

First thing I'd look for is to see if fuel will come seeping out the fuel line with carburetor removed, tank about half full of gas and gas cap on and saw sitting in normal upright position - It should be able to pressurize the tank enough just sitting there that fuel will come pushing out the fuel hose (the end that attaches to carburetor) if it doesn't , give the saw a little shake while it sits and see if fuel comes out, if not then you have a cracked fuel line or plugged fuel filter. If it does, then it is time to pop the pump diaphragm side of the carburetor off and check the fuel inlet screen to see if that is plugged, if that is clear then you likely maybe have a sticking metering needle , because otherwise that little bit if fuel tank pressure should be enough to get *SOME* fuel to the carburetor that normally should pass through, allowing it to fire at least when choked, with or without a working impulse hose.
If you tried a known working carburetor than I'd say you likely need a new fuel line which is one of the MOST common issues I used to see on Stihl saws, so much so that I used to keep an assortment of fuel lines in stock for most of the common models I'd see.

Alternatively, your fuel tank vent may have failed (It should hold a LITTLE bit of pressure in the tank - If you blow into the unhooked fuel line gently, then fuel should come shooting back out as soon as pressure is removed, so I don't recommend doing it by mouth or with a air blow gun - One of those computer keyboard duster spray cans may do nicely for such a test if you have one handy.. or a long piece of regular 1/8" fuel hose you can stick one and in your mouth and hold other end over the saw's fuel line and give a quick puff of air, then fuel should shoot back out of the saw's fuel line...) If that little pressure test trick on the fuel tank does not work you have a cracked fuel tank, bad gas cap, or failed tank vent.

[SUKI]

I would be leaning to metering diaphragm being overly stiff myself.

Beside most of the Zama built in the last few year are just not holding up like they use to. I finding main nozzles leaking, acceleration plungers worn out, worn out throttle shafts, etc. This has happen since Stihl took controlling interest in Zama. And you find most Stihl dealers can't provide repair kits for the carburetors instead they are just selling replacement carburetors.

The good news here is this saw uses the older Zama and Walbro carburetors which repair kit are still available for. Or at least the metering diaphragms and gaskets are.

[Arkie]

Do you have a pressure or vac tester?
With a blood pressure bulb and 0-5 lbs gauge you can test the fuel line to the tank, the carb pop off pressure, the pulse hose instead of just doing a visual test. You can rig up a pressure test tool for less than $20. You can find lots of info online about how to test pressure test the carb and fuel lines.

Yes about the pulse hose. It operates the carb's fuel pump.
The pulse hose should fit onto the nipple snug. I would replace it if it's old and hard to access while you are looking in that area.

I was recently given a 034 for parts that owner said had low compression. Saw had accumulated lots of nasty oil and dirt on it's outer surface, looked really bad.
Pulse hose was old a split. All else ok. It's being used in the woodlot quite often.

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