Somehow I missed this thread, so hope a late reply is of some use.
I have the 40" MES from Sam's too, and have had the same problem with getting to heat. I think I have used the MES about 6 or 7 times, and twice it had the problem of getting to heat. The 1st time was the extension cord, the 2nd was 10 racks of ribs on 4th, and that was scary because 70 miles away people were expecting those ribs. The 3 uses since have been small quantities of food, so not a good test.
However here is my current procedure:
1. Preheat MES to 270, no water pan. Be sure and spray the racks with pan if you want easy clean-up. No extension cord.
2. While preheating boil water, I have a electric hot plate for outdoor use that I use.
3. Throw wood chips in some water and let soak during preheat. BTW I found a neat little scoop $2 at walmart, I use for the wood.
4. Get meat ready to go into MES.
5. I used to load water, meat, wood. The racks already in MES. As I said I have only been smoking small quantities since the 4th, so only using two racks most of time. Now I keep the racks I intent to use out of MES during preheat, and put meat on those racks, when ready I then load in MES. The idea here is only have the MES door open the absolute minimum time, to keep heat/temp up. To help, I have a prep table setup next to the MES with everything ready to go.
*I used to load water pan at same time, now I load water pan about 15 minutes prior to loading everything else, again I do this very quick so the MES doesn't drop much in temp.
The temp drops to around 180-200, provided I keep door open to a minimum.
At this stage, you really want to absolutely keep the door closed, no peeking! That also means you need to be careful when you load the meat everything is in the MES the way you want it, meat, water, temp probe if using one, etc. I have had the temp probe fall off the rack when pushing another tray in, and not notice this. Then having to correct this by opening the door. This can add another 30 minutes to getting MES up to cooking temp.
4. I now do a hard reset, (turn off digital control, unplug electric cord). I reset the MES to my desire temp usually 225, and set cooking times. My thinking here, this serves two purposes. 1st, when the MES failed to get to temp previously I did hard reset sometimes two and the MES finally got to temp. So now I just automatically do the hard reset when starting the smoke. 2nd, I want to make sure the heating element is on, I have no clue how fast the sensor when detecting the temp drop turns the heating element on. So by hard reset, I know for sure the heat element will be on and working to get to my set temp.
5. The 1st hour of my cook I check the MES and Taylor every 15 minutes to make sure the MES is working properly and achieving the desired set temp.
I know a lot of this is obvious, but I thought a detailed description may help new MES owners.