I have a dewalt air compressor model d55155 will not bulte up any presure changed the cold start valve and the reed valves but not the reed valve plates it seemes like like now i have air coming out the oil fill and dip stick hole could i have installed the reed wrong or could the rings or piston be the problem do need your help

which model of dewalt
to may variables

ether a ring problem or reed /non return valves

if compressor is a direct drive or stand alone compressor belt driven
the compressor has gaskets and reed valves that can leak or wear

probably part # 30 here

http://www.ereplacementparts.com/dewalt-d55155-type-compressor-parts-c-1009_3079_3080.html
Dewalt D55155 Type 1 Compressor Parts

I don't what you mean by a "cold start" valve? Too much typing for a guess.

It's on the bottom, right hand side of the tank if you are facing the tank side. You can download the owners manual from this link. It is at the upper right side of the page in the section marked downloads.

DeWalt D55155 parts and owners manuals

The cold start valve will close when volume of air from compressor is sufficient to overcome spring under pin (allows the motor to come up to speed). Evidently your compressor is producing very little air. Usually the problem is leaking or broken reed valves or gaskets. Remove the head and look for torn/ leaking gaskets and replace as needed. Examing the reed valves and seats and look for broken cracked reeds or worn seats. Some of the valve plates used in Dewalt compressors are made of aluminum and would fail. Parts are available at www.toolpartsdirect.com or local dewalt service center. Good luck with your repair.

Could be leak or faulty valve plate in head. Use soapy water and spray all fittings including drain valve and pressure regulator. Repair as needed. If no leak found suspect problem with compressor. Try simple test, with compressor running and has reached max pressure (60psi) remove air filter and feel intake for suction. Be carefull could be hot. The suction should fairly strong. If no suction or actually feels like air is blowing out of intake, suspect valve plate. Parts are available at dewalt service center or www.toolpartsdirect.com. Good luck

Dear,
You required to replace the valves assembly,
Cylender and piston also need to check for any damages before ordering parts for valves.
Regards
Ashfaq

have you turned up the regulator, the big black know by the output fitting

You may have to open andclose it a few times cuz it may have trash or be stuck

The bleed valve is an unloader of sorts that allows the compressor to start with-out a load. It closes when the pressure in the airline reaches about 20-25lbs with good volume. If air volume is not sufficient, the valve will not close. To solve the problem lets do a few tests. A long cord will reduce power and reduce air volume. Try powering the compressor with-out extension cord. If bleed valve closes when you do not use a cord, the compressor is not getting enough voltage, use shorter cord of the 12 gauge quality and more hose to reach work. If valve still does not close, check for air leaks on all fittings including around pressure switch and drain valve with soapy water. Repair as necessary and retest. If no leaks were found, temporarily plug bleed valve port with screw/bolt and run compressor till set pressure cut-off while counting minuites/seconds. The compressor should fill and shut off within three minutes or so. If it takes an unusually long time to fill, then the reed valves /valve plate is worn and leaking pressure back into cylinger. Leaking valves will usually result in very hot discharge airline/air. Reinstall the bleed valve after test. Parts and partslist are available at www.toolpartsdirect.com . Good luck on the repair and email if you have other questions.

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 WWW.toolpartsdirect.com 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