Hi there I'm hoping to get some help trying to diagnose a problem I've had for some time which just got worst today...

Initially I thought I had the hot start issue. My symptoms seemed to match pretty well. Cold starts were fine. However, if I shut the car off after it was at normal temp, let it sit for a few minutes and then try to restart it, it will crank and crank but will not fire.

So after reading up on the hot start issue a few months back I gathered that a way to get around the issue is to apply some gas if the engine is cranking but not firing. So with this in mind I made sure to try if it ever happened. Well a few weeks went by and nothing happened. After a few weeks it finally happened and I had a chance to try the workaround by pressing down on the gas... but no luck! The engine would just continue to turn and start. I let it sit for a few more minutes, and tried again and boom, it starts. THe start was rough at first but quickly settled into a normal idle. I didn't think much of it at the time and to be honest, it is pretty tough to recreate the issue with any consistency.

A few weeks went by since, and today was the worst. I was downtown picking up my gf from work. So I am on the side of the road and shut my engine off while I waited. It must have been around 7 mins or so, she gets in, I try to start the car and it just starts cranking but doesn't fire. I'm thinking no big deal, its happened before, just wait a minute and try again. It seemed to work in the past. Not so this time. I tried to start the engine 2 more times (over a span of 10 minutes) but no luck. I figured I'd better understand what's going on before I drain my battery trying to start the car. Note that during my attempts, I tried both pressing the gas and not pressing the gas. I also let it turn for a max of 5 seconds at any one attempt.

I step outside and it's pretty noisy downtown, but one of the sounds I think was missing was the sound of the fuel pump. I swear I used to hear it go on when the key was turned to position 2. Can anyone verify if this is supposed to be the case? I'm talking about the one I can normally hear at the back right. In any case, the fuel pump definitely doesn't turn on, and I later verified this in my driveway (when I finally got home).

So at this point I'm out of ideas. I checked the fuse panel but doesn't seem to be any fuses blown and none that seem to be related to the fuel pump. I don't know how to check codes. In any case, after about another 10 mins of tinkering I figure let's give it another shot. Turn the key, starter starts turning and boom! Engine comes alive! WTF?? Again, it started a bit rough but settled into a normal idle within seconds.

So now I'm driving home and decide to get gas, and also wanted to see if I could recreate the situation. I go to a gas station near my house, just in case. Also, I should mention something else strange, at first I was a bit low on fuel (just below the 1/4 mark, but no warning light yet). After I got it started the fuel needle was at the empty mark (didn't rise at all, and still no warning light). After I filled up and turned the key to position 2 the fuel gauge seemed to work normally again.

So after filling up and trying to start the car, exact same problem. This time, I tried starting it a couple times with no luck. Waiting 10 mins or so, tried again. Car did fire once but died immediately. Waited 5 more mins, tried again and it starts.

Here's some other notes / questions...

- wiring harness was replaced just under 2 years ago by MB
- am I supposed to hear the fuel pump in the rear right when the key is in position 2?
- when the engine did start and was running, I could hear the fuel pump in the rear right
- 170,000mi, full MB service history with previous 1 owner
- post that seems closest to my issue but no resolution / update: http://www.peachparts.com/shopforum/showthread.php?t=206180&highlight=fuel+pump+w124

What's going on???