[Doug_B]

I am trying to figure out a problem I am having with my fuel pump on my 89 TRX350D. At first the 4wheeler started stalling out and I could not hear the pump running. I replaced the pump with a Mr Gasket low pressure pump but it runs all the time when the key is on. The oem pump never did that. I'm trying to figure out how it knows when to cut the pump on and off. I know it should come on for a second or two when you first turn the key on, and then be on when the engine is running and there is spark, but this pump runs as soon as you turn the key on and never shuts off. Should the pump also run constantly when the engine is running? Is there a pressure switch inside the OEM pump to tell it when to cut off and back on when the engine is running?

 

[Helmut]

Welcome to the forums. That model has a fuel pump control unit that cuts the pump on and off. Shadetree said he replaced his fuel pump with a low pressure pump from Advance Auto Parts and it works perfectly, so the problem might be the fuel pump control unit. I believe it's located under one of the rear fenders.