I've never heard of doing that.

You would know because it is disappearing, not leaking onto the ground, not leaking somewhere in the engine bay, and not getting into the engine oil or transmission fluid.

That is a separate thing to diagnose. I'm not sure what part you are referring to here. If the battery doesn't get charged, the car will not start. This likely would not cause a fuel pressure sensor error code.

The Mechanic says that it is not starting then likely the starter is gone. He doesn't seem worried about the water loss. I will keep an eye on it once the car starts.
Right now I just need the car started..I will likely have to rent a car today

He thinks it needs a starter? If the starter is the problem he would say so not THINK so. If the engine cranks (this doesn't mean it starts) then the starter is fine.

You had the starter tested back on January 20th . I bet it hasn't gone bad in twenty more starts since the engine got taken apart etc. There are too many coincidences here: The engine just got "overhauled" and now is losing coolant and also the starter is bad? Odds are slim.

. . . and the "mechanic" not being concerned about coolant loss is not surprising any more. Seems typical for this mechanic and others I've seen like him. If I repaired a hundred of your car, none of them would lose coolant like this after I gave it back to you, unless some other thing failed (like water pump, heater core, hose, etc.) and coolant was leaking out there.

Now you have an engine that won't turn over and no explanation for where the coolant is going.

Next step in my book: Take it back to this "mechanic", point at it, and cry. He should have warranteed his work for more than a couple of weeks and a couple of hundred miles.

If that isn't an option, then pull the spark plugs and crank it over. My bet is you'll see a bunch of coolant get blown out.

Engine does not crank any more..only a click sound. The mechanic says that the starter was probably tested without load..under load it behaves differently. I had taken it to autozone and they tested it and said it runs like new. (I am not sure if their test is under load) . After the car was fixed(overhauled), the starter seemed to be just fine (started with no abnormal noises) . On a side note..Funny thing, I took the 275 amp fuse that provides to the starter to Lordco. They tested the fuse and told me it was not "continuous" and when the fuse was out of the car, no electronics worked ..but I put the same fuse back in the car and all the electronics worked..I have no idea a "non continuous" fuse would have any effect whether it was in the car or not. The mechanic seems to replace parts to test if all is good..He said that hopefully it is not the high pressure fuel pump, I guess that might be the next part to replace if needed.

Is there a way the mechanic can test if the starter is working or not rather than just replacing it ? Also the fuel rail pressure sensor ( this part alone is $155 at the dealer)

Yes, the auto parts store tests it without load if it is not installed on an engine during the test. You can still tell a lot about a starter under no load, but yes not everything.

If the engine doesn't crank, the problem isn't any kind of fuel pump. If this mechanic is suggesting this, he'* trying to pull one over on you.

Next step in my book: Take it back to this "mechanic", point at it, and cry. He should have warranteed his work for more than a couple of weeks and a couple of hundred miles.

If that isn't an option, then pull the spark plugs and crank it over. My bet is you'll see a bunch of coolant get blown out.

Normal diagnostics seems like a foreign concept to this mechanic from what I can tell. Engine ran but coolant disappearing, now starter only clicks.

Step 1. Try to turn engine over by hand, at least two full revolutions. Easy to do, especially with a lift. If it turns over by hand then could be a bad starter so proceed to Step 2. If not then engine is seized or hydrolocked, proceed to step 3.
Step 2. Troubleshoot bad starter, check electrical system connections, battery, etc.
Step 3. Troubleshoot seized engine.

If the engine doesn't crank, this is not the problem. If the mechanic told you that the starter is unable to turn the engine over because of a bad fuel pressure sensor, then the mechanic is the problem.

So the mechanic worked on the car today for just over 2 hrs. He replaced the starter and the fuse. The car started up (with slight reluctance) but no engine code lights .
He said to keep an eye on engine light as if it happens, it is likely related to fuel rail pressure sensor and we would have to replace that..He wasn't worried about the water loss.. the exhaust was giving white smoke but he said it is normal. I will keep and eye on the coolant level...hopefully it was just air bubbles in the system.