Coleman 1600 pressure washer

no I dont have manual

This is the best site to get ANY Honda manual, just send them a search request and within 2-3 hours you will hold your manual in your fingers.

Usually, there are spaces between the pump and head portion of the pump. This space is not sealed and will allow water leaking past the seals to come out. There may be a seal kit available, however I have had better luck just changing out the whole pump. There are many available on ebay. Search for one that will use same mount and hoses. Once the seals are gone, the pump will never be the same (may nickle and dime you the death).

Well, you may be out of luck with Coleman's customer service. They have gone out of business, from what I understand. I have a pressure washer just like that one. You may be able to find one on ebay, or one online that someone has scanned.

This sounds like you have an inadequate supply of water to the unit. Make sure your supply faucet is turned all the way on, use a 5/8 or 3/4" hose from the faucet to the unit, and use a smaller tip on your spray nozzle to minimize the amount of water you are using when working.

Sounds like the valve in the handle is sticking closed. May have a broken spring, or maybe a part is stuck..
I say take it apart, and the answer will present itself.. Play with it with nozzle out too... Maybe something is stuck after storing so long and will loosen up.. Fingers crossed

I've never used it before what plugs in where, the 1210 powermate, Pictures would help

You're describing a number of issues related to old age and maintenance. First, you've likely got a mechanical timer that is getting stuck. If the price of replacement is outside your budget for an old warhorse....

Second, in come cases, the timer takes care of water level...in most, however, there is a float or aeneroid level sensor. If it is a float...it may be clogged/jammed with detergent or debris. Located in the wash tub near the front. Clean it up. If it is an aeneroid, it has a tube going from the tub to the lower part which hooks into a 3 inch or so flat sided round item with two wires coming out. With the power off, test it by blowing and sucking on the tube. Blowing into it should open the switched leads ...sucking should hold a 'vacuum'. The pressure of water opens and closes this switch to determine water level.

is the washer noisey when spinning? If so its probable that the main bearings are worn, & losing the original grease into the wash tub. At 10-14 yrs old its probably not woth fixing (assuming parts are still available)