Old power washer with Interpump, information or advice anyone?

[Effsweet]

Hi all,
I have a GH 800P power washer, bought new about 40 years ago
its been in dry storage for about 35years.
Honda G150 s/valve engine & an Interpump W50 pump.
I want to recommission it, but I can’t find any reference to it on the web
Could anyone advise how to drain the pump of oil & the volume to refill with? Doesn’t seem to have a drain plug or a dipstick
Any pointers or suggestions gratefully received
Thanks in advance: effsweet

s

 

[500e]

Welcome some one will have an idea maybe @8ob
Please take the caps off it's shouting we are nice people here

 

[knighty]

are you sure it's just W50 and there's not more numbers that've worn off?

can you turn it by hand?

 

[carbon]

Interpump W50 pump.

Can you add a picture as none of the information about interpump’s I have lists a W50. There are some newer pumps that start with W50 but they have an extra two digits

 

[Effsweet]

500e: Apologies for shouting. Didn't realise I'd typed in bold. Hope I've got that sorted now
Knighty: Definitely W50, see pictures below
carbon: Pictures below show confirm Pump type & S/No also pictures of top of pump (note Schrader valve),front face of pump with inlet & Outlet hoses attached, & one side of pump.
Closer inspection this afternoon suggests there's a drain plug to the left of the inlet hose that 17mm oe spanner fits & it will slacken with gentle hand pressure. Not yet removed!
Interpump started up in 1977 (?) so this will be early production As I guessed earlier Invoice is dated 1983 I'd guess design was changed significantly No info on www.interpump.it either that I can find.
Thanks for all your comments so far. Any more help or suggestions very welcome
Hoping my photos file sizes aren't too big for the system - ah 3 thumbnails & 1 full-size it all seems very easy to upload

Thanks again: effsweet

 

[Effsweet]

Knighty, sorry missed replying to your question Can I turn it by hand? I don't know, I took the engine cylinder head off 2 or 3 days ago as I couldn't feel compression when gently pulling the start rope 4 or 5 times All seemed good with no sign of stuck inlet or exhaust valves. I take it you mean does the pump itself turn & could the pump be seized? I'm pretty confident the pump will be rotated by the engine output shaft but will confirm to myself tomorrow
Thanks: effsweet

 

[carbon]

As it’s a two cylinder pump the schrader valve was used to pressurise the diaphragm that is inside the housing in an attempt to reduce the outlet pulsing. Other manufacturers did something similar at the time but usually externally mounted the damper.

 

[Effsweet]

Carbon, Chris, thanks for the info. Today I assumed that the schrader valve allowed you to pressurise a membrane of some sort to absorb/smooth out pressure pulses. 40 years ago I had no idea pressure washers were so complicated
effsweet

 

[frank horton]

for me if the engine runs just go for it.......
u can get a cheap chinese bronze pump 2.500psi for around £60.......

 

[Effsweet]

Hi all,

to wrap up this thread, I now have a .pdf of the operators manual/technical drawings & parts list for the pump

I can post it here if of you feel its a useful resource? Let me know & I'll put it up as a separate Post for information

Thanks to all who have helped &/or commented