2006 Mitsubishi Montero Starting issue

This could be a "toughy". Apparently the dealer has been using the "shotgun approach", 'cause they can't figure it out either, but, let's try. The only thing I ask is that the answers to questions is acurate and if you don't know the answer, just say so. Don't guess, or we'll just be going around in circles. The first thing we need to determine is what is missing when the no start condition exists. Is it spark, fuel, injector pulse or all? This could be tough if it only happens once in a great while. All the items that have been replaced affect all of the above, and when we find the problem, instincts tell me it will be something very simple. We have to look "outside the box" so to speak. Please advise.

OK, Over the years I've had just a handful of vehicles with your same problem. I would keep them at the shop, drive them everyday, use them for parts runs, drive them back and forth to work, everything, and they would run flawlessly. Give it back to the customer and a day or two later, it would stall. By the time I got there with the tow truck, it would start right up. FRUSTRATING, to say the least. But, it all comes down to knowing what part of the system is failing when the "no start" condition exists so we can narrow it down. Here is where you come in. Not knowing what your mechanical ability is, maybe you can have someone help you with this. It sounds like you are losing fuel pressure on startup. But we are going to check spark first. We need to hook up a regular ignition light to any plug wire and extend the light into the passenger compartment so you can see the "flash" of the light as you turn the key when it fails to start. This may sound a little confusing, but anyone who has experience with a timing light, will know what I'm talking about. What it boils down to is, when the motor won't start and there's no flash, we have no spark. Then, we have a starting point. If the engine won't start, but we "have" a flash, then we know it's not a spark problem and go to plan "B". I still have a unit I built, that would monitor all 3 system at the same time, but that doesn't do you much good.
If you can do this, or have any questions, get back to me. We'll find the problem, it's just going to take some time.