Put new in line fuel filter, but will not fill filter up with gravity flow. needs air to get the fuel flowing. is there a special filter to use on this?

This sounds likely a badly routed fuel line that is getting hot and causing airlocks. The fuel delivery is slow, the gas heats up and vaporizes causing an air lock. You can test by removing the fuel line and with no engine running, run the contents of the fuel tank into a container. Do you have good fuel flow?

Or the float bowl isn't venting via its overflow pipe.

If the engine does not have a gravity fed carb. then there will be a vacuum pump on the engine, this takes a pulse from the rocker box to work a diaphragm, this in turn pulls fuel from the fuel tank, if the pump is faulty then fuel will not fill the inline filter, the pumps are not really serviceable , a quick check to see if its working, there will be three hoses to it, one to the rocker box, one from the fuel tank, and one to the carb, remove this one, put the end into a suitable container, now crank the engine, there should be a flow of fuel.

In order to answer specificly we need Make/Model/Year/Engine Model/Deck Size.

I was mowing along on my LA145, which had about 200 hours on it, and it slowed down then died. Before it died, it was acting like it was losing power. It felt like it was only firing on one cylinder. I waited a bit and it restarted after a lot of cranking. I made a couple mowing passes, and then the same thing happened.

Because I have mowed commercially for many years, I know my equipment inside and out. This mower was in top running condition and should not have been acting this way. There were no engine misses, no backfires and it was not normally hard to start. I knew the carburetor was clean, the coils were good, and the plugs were new. The fuel filter was recently changed. I got off, lifted the hood and gave a general inspection of the engine compartment. I noticed the fuel filter was nearly empty. I pulled the hose off the tank side of the filter and saw there was no flow.

The gas should gravity flow from the tank to the filter, if the tank has a good supply of fuel. Not that I recommend this practice, but I have no problem with doing it myself....I wiped the hose off and blew air back into the fuel tank. It helps to take the gas tank lid off first. After I got a good flow of air going back into the tank (it required several lungs full of air, you can hear the bubbles) the fuel began to gravity flow back through the hose at a decent clip. This fixed the problem. There is likely silt build up in the tank and it settles at the output port blocking the flow of fuel.

The problem repeated itself several times last summer. Back at the shop, I used compressed air to blow the line clear. The problem has not shown up in quite some time.

probably needs carb rebuilt and needle and seat put in

I am pretty sure that your mower doesn't have a fuel pump... What kind is it? Mowers are gravity fed and pulled by the carb suction. Carb dirty or bad= no fuel flow. Check the outlet of the tank there could be a piece of trash in it or in the fuel line preventing flow. Try a new filter and make sure the correct filter is installed as it will cause those symptoms. Also if it cranks an runs like normal without you dumping gas manually in carb, then its fine. Not all filters are going to be totally filled especially the wrong ones. Half is normal. Id need more details to know give you an sure accurate answer.

vacuum though there is a prime (gravity) position

Does it use gravity or a pump? If gravity, check the fuel line for internal disintegration. Air filter is clean, right? If your float does not move freely, it can restrict fuel flow also. Need for choke indicates that fuel is not being supplied, so check that it can flow by loosening the float bowl and catching the fuel. If slow, remove the bowl, and check the unrestricted flow.

there is a screen molded into the tank stick a coat hanger wire threw the hose fitting and put a hole threw the screen and just install a better filter in line

I have fuel flow (gravity flow) past the fuel filter. I can start the engine after putting fuel into the carb. but it does not pump any fuel from the fuel line. Gas burns in the carb and engine dies. How do I check any of the componets without replacing them?

gas tank gravity feeds fuel to the carb. if you pull the fuel line from the carb, fuel should flow out of the tube. if it does not, then either the vent hole on the gas cap is plugged or there are contaminents at the bottom of the gas tank preventing fuel from flowing into the fuel line.