As par for the course here, you're being given a mix of some good and some pretty inaccurate information.
From your postings, there are several scenarios that are possible.
was running fine, and was just not used anymore, and it had good fuel
in it, and a good coat of oil
on it, which just 'dried up' (evaporated) leaving the rack and pinions, and likely the p&bs gummed up. If there is little or no rust on it, and someone hasn't botched a reassembly after cleaning
or attempting to clean it, this will probably be your best case scenario.
Just because there are scribed marks doesn't mean anything is wrong; as you've seen in the book, those marks are made whenever the pump
is disassembled to aid in its reassembly.
With 600 hours on it, in this condition, if you bring it to a shop, much will depend on which shop you bring it to, and if new parts
are available for the 40 year old pump. Also, you'll almost certainly have to retime the engine by adjusting the shim pack, especially if they change any internal parts
Another scenario is that the engine was left with bad fuel
in it, in which case the lap fit internal parts will be corroded and have to be replaced, so the point is moot: it has to go to the shop, and you'll have to deal with retiming the engine when you get it back.
A final scenario is that in its time of disuse, condensation
has wreaked havoc
on it, it was left with bad fuel in it and will have to be replaced entirely. Sucks to be you if that is the case.
If it were me, I'd do what you're doing; see if you can free it up. If you're uncomfortable with trying to clean it yourself, then don't. But make sure you check out the guys you bring it to before you bring it to them, and get an estimate first. My first choice, all other things being equal, would be a shop that specializes in ag equipment
, but the quality of shop service
in my experience can best be quantified as a crap shoot.
These little pumps are very simple, if the only problem is that it has gummed up internals, and the engine was running good when it was laid up, carefully taking it down, cleaning
, inspecting and reassembling it as per the manual will be the most economical route
to take, if you feel you can do it.
It can be done, and I have done it more times than I can remember.
Nothing wrong with taking it to a reputable, conscientious shop though.