Audi 200 not starting, fuel pump?

[MHCAudi200t]

What's up everyone?

This past Friday I ended up working late, and I decided to leave the 200 at the shop as usual. Once I got back I had a hard time getting it started, i had to crank it for a good 10-20 seconds.
Once it turned over and it turned on every time the RPM dropped to idle it would turn off. That happen a good 3 times till the fourth time I just pushed to gas a bit to keep the RPM above idle and took off. Once driving I didn't have any issues and drove home. The next morning once it was time to go to work I got in cranked it and turned on with out any problems. Once I got to the shop I parked for 20 min. And I had to move so an other employee could move. Again it started giving me problem and it turned off as I mentioned above. I kept trying and could not get it to run, since we had to leave to install I just left it. All day till I got back and was checking it out, one of the people at the shop suggested to hit the gas tank to see if it was the fuel pump. We smacked the gas and it turned on.
Before I start throwing parts at it is there any thing else I should check?
Any advice/comments are welcomed!

[themagellan]

I was having a hot start issue and it ended up simply being the ECU boost line.

If you physically hit the gas tank while cranking and the heard the fuel pump come on, I would put a lot of money on a bad ground to the fuel pump or something wonky with the unit. I wouldn't consider that "throwing parts" at it.

The best 25$ I ever spent was a hand operated vacuum pump, using that I tracked down all intake leaks. There were a lot.

[MHCAudi200t]

I was having a hot start issue and it ended up simply being the ECU boost line.

If you physically hit the gas tank while cranking and the heard the fuel pump come on, I would put a lot of money on a bad ground to the fuel pump or something wonky with the unit. I wouldn't consider that "throwing parts" at it.

The best 25$ I ever spent was a hand operated vacuum pump, using that I tracked down all intake leaks. There were a lot.

Well my brother started hitting it and did it around till he got to a spot where he stopped and continued hitting it. Thats when the engine started to turn over and from ther i just pushed on the gas a bit and it turned on. I just wanna make sure i know what the problem is before i order parts. I wanna do it right the first time. I appriciate the feedback

[vt10vt]

Sounds like more than vacuum leaks to me, leaks would, generally, provide a more consistent starting problem than this. In my experience intermittent usually means electrical, not mechanical. The fuel pump is triggered by one of the timing sensors (can't remember if it's hall sensor but I think it's the crank sensors...) so to see if the fuel pump is at least running consistently, when it won't start crank it for a second and then listen for the pump to run for a hot second after you stop cranking. Should run for a second or two after the motor has stopped rotating. You might need to have someone crank it while you stick your head in the trunk, I just have to pull the carpet FP cover back to hear it in my Avant but I bet your rear seats will make it more difficult. From the smacking of the fuel tank it does sound FP related