Drain to Laundry is leaking sewer gas smell

[Jefehebes]

Hi All, cannot figure this one out. I know there has been similar posts.

I have a split level home, Laundry machine is on the bottom floor, plumbing is in the crawl space.

When I start the laundry, the sewer smell starts building from the drain hose. It takes about 30 seconds then slowly starts building more and more. This only happens with the laundry.
I attached a picture of my plumbing and a picture of the P trap.
I think, by the end of the cycle the gas smell stops coming and it starts to dissipate, kind of hard to tell.

I have tried pouring a bunch of water down the drain before starting the laundry, that didnt work.
I climbed on my roof and looked down the vent, I could only see so far but I didnt see any clogs.

Is it the trap? Vent? Washer?
Can anyone help me on this, Its driving me crazy?

Jeff

 

[Terry]

You look to have it plumbed right. I match over the standpipe would perhaps tell you if the trap was dry and allowing wind coming up the pipe.