Service engine light keeps coming on after pressure builds up in gas tank. The light goes off once we take gas cap off and release pressure.We have replaced cap.

did you reset codes after every repair ? is it a newer car ? there is a sensor in canister called a netural pressure vapor sensor they tend to leak or stick .causing evap codes , I chased the same code ,it would go out for about a week then come back in my case it was the new gas cap it was the wrong one for my car. it keeped building pressure in gas tank . and could hear it hissss when I would open it fuel up .

I don't know much about jet skis but it sounds like its building pressure in the gas tank as you have said..Does it have the original gas cap.. Sometimes the original caps have a very small vent hole. People replace them with one that dont....if it was a car it would be called Vapor lock....it's when the pressure in the tank becomes greater then the fuel pump..Might be a little hose that goes to the carb... Supposed to burn fumes..if it's clogged it builds pressure in your tank... Something like this is going on..If you take the gas cap off and hear air sucking into tank this might be your problem..Hope this helps..

You have some otyher issue here besides the pressure problem.

You have a check light on & pressure when you
remove the gas cap,so the question to you is,
why are you not getting the codes & repairing the
Evap System

Pretty simple I would say !!

I am not sure I understan tghe question. You should not have a lot of pressure in the tank. There are hoses that capture any vapors that are in the tank and eleviate pressure build up.
Most often I have found the engine light on because of gas tank vent, such as loose
or bad gas cap or the vent valve stuck open. The computer does a cycle ever so often
and maintains the vent pressure build up in the gas tank and vapor canister, and if the purge valve sticks open the computer gives a check engine light and code as the pressure is not in the vapor storage tank when called for.
If your worried about no pressure at all then I would change the gas cap and see if this helps

the code doesnt refer to gas cap it is just the most common problem associated with PO440 what it means is the tank isnt building pressure can be caused by leak loose vent hosae damaged canister look for loose connections at tank will not be fuel lines only vent

hope this helps give you ideals plz leave a comment and reply if you have more questions

check the charcoal vapor canister located under the hood,it reclaims the vapors and can plug up

Make sure that the gas cap is the correct one. If the gas cap was replaced with a different style or a locking cap this will set off the check engine light. It can tell there is a problem because it measures the built-up pressure in the gas tank. So the pressure is not building in the tank due to a loose or incorrect fitting gas cap or a loose,cracked fuel line, or bad check valve in the charcoal canister for the fuel tank vapor release line.

Yes it can trigger the service engine light if the cap is loose replace it so it will build up the pressure in the tank. the seal is probably worn out and won't seal the preasure in

A loose gas cap will sometimes trigger the service light to come on.  Since this appears to have happened on multiple occasions I can assume that this is not the problem but may be associated with it.  The level of gas in the tank affects the amount of atmospheric pressure in the tank. There are multiple things that could set off the light, one being a loose or defective gas cap, and the other is a fuel vapor return valve.  I'm not sure of the exact type of fuel system you have so I cant give a more exact answer.  If you wanted to give something a shot before bringing it into the shop, you can simply replace the gas cap first, a very cheap try.