Hello all
I have a 2000 Mercury Mystique I recently acquired.
It seems to “quit” running if I go up a steep hill. I’ve had it towed, get to a flat place, let it sit a few mins and it starts again. I took it to a garage, mechanic thinks it’s electrical, but has only dealt with this once before and cannot recall how he did that. lol. 
help please…
If it runs fine other than that I’d be inclined to want to know if it has an inertial sensor. That’d be designed to sense an accident and shut the fuel pump down. If it were malfunctioning it could be shutting the fuel pump down based on simple angle of inclination.
I agree. The fuel pump safety shut-off is a good place to start. Check your owner’s manual for its location. It’s usually in the trunk or rear of the vehicle.
Just for fun you might want to check the fuel pump’s pressure.
Does the car behave differently with a full vs low fuel tank?
This is a long shot and it would be the last thing I would look for, but there may be foriegn material in the fuel tank. Back in the 80’s a customer bought this Chevette that was on the lot and it would shut down intermittantly. The service manager was stumped as they could not figure this one out. As a last resort I was instructed to r&i the fuel tank and that is when we found rocks and maple leafs floating around inside.
Like I said, it’s a long shot but…
I have an even LONGER shot, but the triggering event reminded me of a problem that my little sister had on a Celica once. It had a bad time/temperature switch that is supposed to enrich the mixture on a cold start. It just happened that whenever she went up a steep incline, like a parking ramp, it would kick on and flood the car. After a few minutes, the car would restart. She took it to multiple shops until she found someone sharp enough to figure it out. The chance that this is the problem here is nearly zero, but it gives you an idea of the sorts of things that can go wrong and how they can be triggered by unexpected stimuli.
Rule out a dirty fuel filter …by changing it. Have the fuel pressure checked. It may be low. Remember that the engine is working harder when the car is pulling a hill, and, therefore, needs more fuel. A dirty filter, or low fuel pressure, won’t have the flow / pressure. {You don’t try only one solution on a problem; but, different ones until you’ve found the right. So far, everything proposed is inexpensive. Taking action is up to you. Of course.]