The Henry J shop manual does not mention any measurements or tests. It simply states that "if the wipers become inoperative, remove the motor and send it to an authorized Trico repair center." There may be kits for them but I've never used one. There is a leather-like flap inside them that dries out over the years and no longer seals which is why they become weak and don't work. I've had one person tell me he was able to soften it up in his and get it to work. My solution is much simpler - Rain X. Get a bottle of Rain X from any auto parts store and apply it to the windsheild every couple of years. You will never need the wipers again. I use it on my '53 J and I haven't turned the wipers on in 15 years (and I drive the car all summer). I drove it to the National in Auburn back in 2004 and we were hit with a major downpour just outside LaCross, Wisconsin and I kept right up at 65 to 70 mph and never had a problem. The rain just rolled right off. Rain X, that's my solution. I'm sure there are places that will repair the pumps. You may want to google "Trico Wiper Motors" or something like that and see what you get. If you do find something, post it on here as I'm sure others will want to know too.
Also, some Henry Js had a dual action fuel/vacuum pump. The shop manuals say the vacuum section on the boosted pump should measure 10" Mercury Min at 500 rpm.
In addition, don't overlook the vacuum hose which goes from the back of the motor to either the manifold outlet or the fuel pump (on those with the vacuum boosted for wipers) as it can be rotten, cracked and leaky which will certainly effect the operation of the wipers.
