uncouple on a grade

[justafew]

I have Elevated one end of my lay out now the train uncouples from the engine.

[Ken G Price]

These are what I can think of.
Where on the grade. At the beginning, at the end, in the middle, on a curve?
Seems that you most likely have a track lining up problem.
If at the beginning or end of the grade then you have the transition from flat to grade at to steep of an angle.
If in the center then there is a dip or rise that moves the couplers up or down and away.
I have had both of these happen when I first laid track.

If none of these then bad couplers or to many cars being pulled and the weight pulls the couplers apart.

[rogertra]

I have Elevated one end of my lay out now the train uncouples from the engine.

Only two reasons, poorly adjusted coupler(s) and or poorly laid track.

Solution?  Fix both.   

[justafew]

Thanks for the help. have gone over all the track no movement and the supports are at the track joints. I don't see any adjustment to the couplers.

[Len]

If the vertical transition from flat to grade, or grade to flat at the top, is too abrubt knuckle couplers can "bypass" each other and you get a runaway train. This is especially true with longer passenger and freight cars, e.g., over 50 scale feet long, and pier/trestle sets with the piers/trestles set too close together creating a steep grade.

You can usually see this happen if you watch carefully as the train makes the vertical transition. If this is what's happening you either need to make the transition less abrupt, or switch to shelf couplers.

Len