Question about Dewalt 3800 PSI Pressure Washer

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Feed from a water tank

Can i connect my dewalt 3800 to a water tank and use gravity to feed the pump and what happens if the tank runs dry while the unit is running

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SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

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Posted on Jan 02, 2017

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SOURCE: dewalt compressor not filling with air drained tank closed valve

Some dewalt air compressors with single cylinder are known to develop trouble with reed valves and /or failed gaskets in head. Parts lists and parts are available at Simple test is to remove air filter and check for suction at intake. Bad reeds will tend to blow air out intake as pressure increases. Failed gaskets in head will cause very high temp at discharge hose. Parts are not too expensive. Enjoy

Posted on Dec 05, 2008


SOURCE: My Dewalt Aircompressor runs but does not pump up

Check valve on tank

Posted on Mar 16, 2010

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The engine runs but the water will not come out under pressure

You must have blown out the cones (thats how the water gets compressed inside of pump) in the water pump-

You could try this though on the back of the washer right on top of the water pump is a black knob about the size of your hand that knob will adjust the pressure try turning it and see although I doubt that is the problem-

A pressure washer is not like a compressor you HAVE to pull the trigger every minute NEVER let it just sit there running without pulling the trigger to release the pressure that Dewalt 3800 psi washer you have is a great machine in fact we own 4 of them and they are pretty powerful and easy to damage if left running alone.


Perry Tradesman

Sep 05, 2014 | Dewalt 3800 PSI Pressure Washer

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I have a liquid cooled 20hp kawi motor on a j.d. Riding mower. The guy next door to me gave me. He has been having an issue with the running. Replaced fuel cap, lines, pump, carb, and spark plug. Still...

Have you checked the fuel pressure with the pump running? If you have a way to measure the pressure at the carb check what it is on gravity feed and with the pump running. Some fuel pumps have a return line to the tank that may be clogged causing the pressure to be high.

Nov 13, 2013 | Garden

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You checked the output to measure 5 GPM? How are you feeding that unit? What are you using for detergent? Have you adjusted the bypass valve?

May 04, 2013 | Dewalt 3800 PSI Pressure Washer

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Sanblaster gravity feed bad media flow

Check that the new gun is compatable with the media you're using in your sandblaster. If you just replaced an old gun with the same kind you should be OK. Check that there aren't any peices of "stuff" in the line to the gun or where the line enters the sand. Next, make sure you are using dried air. Compressing air causes the water (humidity) to condense out and pool in the tank. This water then makes its way through your air lines and to your gun. If the air isn't dried by a filter somehwere on the line the moisture will mix with the sand and make it flow like you describe.

Jul 22, 2012 | RTO Gravity Feed Sandblaster

1 Answer

Can I use a 200 gal. water tank that is not pressurized for my dewalt dp3900 3750 psi pressure washer? the manual says that you should use a water source that has a minimum of 20 psi 5 gallon per miniute....

My name is Dane and I am going to help you solve your problem.
A pressure washer pump is lubricated by the water running though it. You never, ever even start one when not connected to an approved water source. If the manual says that it has to have that presure, don't risk it. I would get an auxillary pump and install on your tank.
Well, I hope I've helped. If you found this information useful, please leave me some THUMBS UP if you think I'm deserving! :-) Thank you! Dane

Dec 05, 2010 | Garden

1 Answer

Got a Dewalt 3800 PSI Pressure Washer with 4.0 GPM with a Honda GX 390 gas engine. Tipped it up to roll it out to my truck and got a big puddle of water with what looked like Pump oil in the puddle. Can...

Could very well be. Did you check the oil level and condition of oil? If its too full or if its light brown milky, then water has entered crankcase. Pressure washer pumps cannot stand to ever let run dry. Even a little. Also excessive idling will overheat pump if it doesn't have a thermostatic relief valve that allows some more cool water to enter pump.If it doesn't have one add one. Find your PUMP mfg and model number. IF it's pumping good now and no leaks, quick replacing the seals will save big future repairs. has lots of info on many pump manufactures. Or get some seals from dewalt.

Aug 11, 2010 | Dewalt 3800 PSI Pressure Washer

1 Answer

When stored oil goes from oil tank into engine, have to drain engine to refill tank and run engine. this is 1969 trident. thanks

This is quite normal. You have what is called a dry sump. The oil gravity feeds through the oil pump. you don't need to drain the engine , just start it and let it idle for a minute then check oil level in tank. The scavange side of the oil pump pumps 3-4 times more than the pressure side.

Aug 14, 2009 | Triumph Trident 750 Motorcycles

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