I'm using my air compressor to sand a car for paint. The sander is an Ingersoll Rand rotary. My air compressor is a Sears 33gal, 1.6hp set up.

The compressor can't keep up with the sander. I get about two solid minutes before I have to wait five for the tank to get back to pressure. Not an ideal way to sand a car down. I painted a car using this compressor before and didn't have any issues using a paint gun. It was stripped using liquid stripper last time.

So what's the weakest link? The motor? The pump? I imagine the capacity of the tank is fine, it just isn't getting filled fast enough.

What can be done? Change the motor, or the pump, or both? I've searched a bit online and what I've found points to a motor with more hp (3 to 5). Thanks,

You need more CFM. Most of the compressors us mere mortals have are 5.9/7.3 CFM @ 90/40 psi. You need a bigger one. You might be able to rent one. Or get a used one on craigslist. Every time I look, all that's for sale are the smaller ones, or really expensive used one.
I tried sandblasting my car with a 2.6/3.7 CFM and got about 10 seconds of blasting before I had to wait 5 minutes for more.

My compressor is 60 gallon, 5 horse, set at 145 psi. It will not keep up with my cabinet shop da sander. Your compressor is way overwhelmed.

Yep to sand blast and paint really you should have a 5 to 7hp
You can get away with a bit smaller if you take breaks, but that does start to suck.

My motor is a true 5hp (made in Canada in the 70's), many of the new China motors may say a certain hp, but they are not even close.

The head pump on mine tossed a rod and I bought a Rolair BK119 head from Princess Auto (Canada's Harbour Freight) it says it takes 5-7 hp. It will stall my 5hp motor above 155psi.
I will say the Rolair is, so far, a nice unit. Parts are made in China, but it's built in the USA.

But new head and motor you're close to a new compressor in cost.

Also.....you need a two stage compressor.

And underwhelming. Thanks for the info everyone.

It's not your fault Ray. Sanders and blasters both consume crazy volumes of air. Most general-purpose compressors can't hang with them. There are some DAs (much better than a rotary anyways) which consume less air, but you'll spend a pretty penny for them. However, they do give you more sanding between downtimes. Still cheaper than spending money, time and effort installing a badass compressor.

I have also noticed that sometimes the regulators will not be accurate and not allow enough flow. I put a couple hose connection before the regulator and connected two smaller compressors together for twice the CFM refresh.

Buy an electric sander

Our guys tried electric tools when our snap on compressor was down for a week. Blew through half dozen electric tools. They won't stand up to hours of non stop use.

Hey man, what about getting your groove on with some chemicals?

Longboard and DA sanders take a lot of air.

Make sure your using the appropriate sandpaper grade or youll spend a lot more time sanding.

Apart from that you need a larger air pump for more cfm.

I use electric tools when I can, buy quality with extended warranty and when they wear out - go do it again. But: I finally sprung for a big boy compressor a couple of years ago - take's a day to move it around the shop (small cluster-f garage) because it is SO damn heavy I have to take it apart n reset the thing. Have I used it for painting n sand blasting n plasma air yet? Nope. But I will I promise.

Here's the secret to a homeowner Air Compressor setup: you can gang several 3 hp ones up until you get what you need. Sounds expensive but Craislist is your friend. My Secret to the Secret is using a very large air tank as a surge tank to help with the extra lil bit needed.

Love to see a picture of your Franken-pressor

Way under-powered. For my blast cabinet and high cfm tools like DA sander, I wound up getting a 7.5hp 80 gallon IR unit. The smaller Craftsman type units simply will not keep up.

Air or electric, you might want to try the 3M Bristle discs. They are awesome for paint removal. You can use them with an angle grinder which is certainly cheaper than buying a new, large capacity compressor.

http://www.eastwood.com/bristle-disc-set-of-three.html