Stihl 025 Starting Problems

linesfarm · October 12, 2019, 08:18:29 AM

I can't start my STIHL 025. I have had it from new and despite it hasn't idled properly for a few years, it has always done the job. When using it this summer it died and I seem to remember there was quite a lot of smoke at its demise. I have used a repair kit to replace carburettor, ignition coil, both fuel pipes, wiring, fuel filter, breathing valve. and spark plug. It still wont start. There is a strong spark, but am unsure if fuel is getting through. Firstly I removed the fuel filter, but still no good. I put a syringe on the inlet pipe to the carb and it started and sounded fine, but hasn't started again since. The exhaust is not blocked. Any ideas? Since it did start with the syringe of fuel, I am assuming the piston, rings and bore are in good fettle. Compression seems to feel good.

btulloh · October 12, 2019, 08:26:11 AM

Diaphragm in the carb has gone bad or the impulse line needs replacing. A carb rebuild or replacement is needed most likely.

linesfarm · October 12, 2019, 08:31:01 AM

Thank you for your very prompt reply, but it is a new carburettor. Can you tell me what a Impulse Line is please?

btulloh · October 12, 2019, 08:40:27 AM

It is a small tube that goes to the carb from the engine and makes the diaphragm pump fuel to the carb.

btulloh · October 12, 2019, 09:03:01 AM

You pretty much proved that it's ok but gas is not being delivered to the carb. Re-reading your post, I see you've replaced everything that could be responsible, but something is still causing the gas problem. Maybe you could try and draw some gas through the pickup line using the syringe. ?? Something in that fuel loop is not cooperating.

I'm just a fiddler and I have an old 026 I keep up that has been through similar issues. I've been lucky and things cleared up for me when I did essentially what you've done. It's always possible to have a kink in the fuel line or something silly like that.

Perhaps a real mechanic will come along shortly with some better ideas!

linesfarm · October 12, 2019, 09:49:55 AM

Thank you for your replies.
I will check for kinks in the impulse line. (I wondered what that extra fuel line was for and equally wondered how fuel was lifted to the engine without a pump!) I'll also have a go with the syringe on the pickup line. I suppose it could be the new carb. It is a Chinese copy! I wonder if I am about to be shot down in flames!!