Glow plugs heat up to close to 1500°F ether's ignition point is about 300°F. The ether will ignite explosively and uncontrollably when it hits the glow plugs.
On the IDI 6.2- All the glow plugs are hot at the same time, but the cylinders are all on different stages of their cycle. So you can get the ether exploding and pushing against the piston while it's trying to come up on the compression or exhaust stroke
On a direct injection diesel- the ether mixes with the diesel fuel when it's sprayed into the cylinder, and helps it to burn, only doing so when the piston is on the power stroke.