Espresso drips out slowly So my wife and I have a Delonghi EC155 espresso machine that we have used for years.  Lately it's been having a lot of trouble pushing the water through the coffee.  We can hear the pump pumping, but the water just barely drips out.  We end up having to pull it 2 or 3 times to get a full shot (or just wait for the drips to fill up the shot glass).

I opened up this machine once before in the hopes of cleaning it, but found almost everything inside pretty clean and the plumbing is all sealed up.  So I'm a little befuddled as to what to do next.

How do I fix my machine so that the shots come out in a single pull?  I wonder if my pump just can form enough pressure anymore - can I measure the pressure?

A note on the grounds:  We have the grinder set to the finest grind, which comes out like a fine sand.  We've had it this way for a long time and not had any problems.  We fill the basket to about 1/2 full (it's a double shot basket, and we only need one shot - the single shot basket was fed to the garbage disposal years ago) and tamp.  I've been tamping more lightly recently, thinking that the problem was grounds that are too compressed to let the water through.

Thanks
As suggested in comment above, descaling or decalcifying your machine may solve your problem. We just run straight distilled white vinegar through ours to do so. Running the machine with distilled water rather than tap water helps keep mineral deposits to a minimum.

Also, running it without water can create an airlock (which makes it take a while for the water to pull through), and allows the pump to spin freely, and so can wreak havoc on, or at least weaken the pump. (I don't know what specific pump is employed by your machine, but this page may apply.) 

Moreover, in the event that the pump has become weakened, it can be helpful to keep the reservoir completely full of water. I do not believe that a normally working machine would be affected too much by the grinding coarseness selected. 

Edited to add: While commercial descaling/decalcifying solutions are available (and might work really well) for this application, the staff on a website selling such reports in the Q&amp;A, "Breville actually recommends using vinegar to descale their machines while you're under their warranty." 

When deciding what to use, it may be to one's advantage to research whether the product is under warranty, and what the specific manufacturer recommends. Also, take into consideration that the unlisted chemicals that might be found in a given solution could put off foul odors and/or flavors (not that vinegar makes a good perfume, by any means).

P.S.  I just found out that the safety data sheet for one descaling liquid contains the following hazard warning (although the company might issue the same warning about vinegar if they sold it): 

H315 Causes skin irritation.

H319 Causes serious eye irritation.