My daughter had the same problem some time ago. I spent ages faffing about with the valve...pin... washing...blowing.... etc. In the end I brought the valve into the garage and got a replacement...cost a fortune!...either 20 or 50 cents, inc VAT. Felt an idiot for not replacing straight away.
btw, I presume we're talking about the valve between the washer pump and the jets? If so it generally is just a push fit onto the hoses, but may be a bit tight to get off. Hot water may soften the hose to enable removal/refit.