1983 Mercedes Benz 280 • 140,342 miles

Car hasn't been driven in last year. Just changed the fuel pump
November 13, 2011.

My car is a 280SE Euro

Nov 13, 2011.
How much gas was in it, or is in it now? If there is not much gas in the car, get some fresh gas, as much as you can, and add it to the fuel.
The gas may be a little rotten or have gummed up the injectors.
Try some high quality fuel system cleaner. The only two worth while are BG44K and Sea Foam. BG44K is better, but you will have to go to a service station or car dealership parts counter to get it. Sea Foam can usually be purchased at an Advance or Auto Zone parts store.
You can put a can in the tank if you have at least 10 gallons in it.
That is about the only way to get the injectors cleaned out and it may take two cans and a little drive time afterwards to feel the difference, but it will gett better as you drive.
To clean the intake and upper valve train, you can pour a can directly into the intake manifold. The best place to do this is into the brake booster vacuum line. Do not reve the car up while the cleaning process is taking place. It will create a lot of smoke from the exhaust, so keep that in mind. After a few minutes, the smoke will start to clear. When it is back to normal, take the car for a spin. Again, it will loosen deposits that will take time to flush out so you may not feel all the benefits right away.
Other than that, if the car ran okay when it was put away, you may have to replace a fuel filter or something, but old gas is a tough problem when starting a car that has sat.

We drained the gas and put new gas in. It is a half a tank. Could the gas filter need changing?

Nov 13, 2011.
Yes, gas turns into a varnish like substance in no time at all and it will clog or impede fuel flow in fuel filters.
That is excellent that you dranined out the tank and put in new gas. Not many people realize that old gas is not really gas anymore.

Didn't work having to pull the tank and take to shop to clean. Any other thoughts?

Nov 21, 2011.
The injectors might be full of old gas that has turned to varnish and the only way I know of to get that cleaned out is by sonic cleaning. There is a place online that is really good called RCEngineering. Com. They will sonically clean, test, rebuild if needed and send you a report on the output and other information for each injector. It is cheaper than getting new ones, but you are not sure if this is going to start the car. There might be somewhere online that does sonic cleaning or some other type of cleaning or has injectors for cheaper. I would guess it is at least part of your problem. That is something you can judge by how bad the gas was in the tank. If it had an in tank pump with the sock type filter the filter would be an indicator of how gooey the gas was since you cranked it over a bunch. It would have made the sock filter really nasty if it was really bad.
Its tough getting a car running that has been sitting a long time.
If you are sure the intake tract is clean. No mice had made a home of it or something like that, and you have spark the fuel system is the most likely thing holding the car back. Gas gets so nasty so fast it is usually the issue with cars that have sat. I don't know if it is safe on the outer part of injectors, I guess it would be as it is bound to come in contact with the plastic part just as gas would. But, you could try soaking the injectors in Sea Foam fuel system cleaner. It is really good stuff and one of the only injector/fuel system cleaners on the market that acually does the job.
Other than that, I think you said you replaced an inline filter if it has one, another indicator of the condition of the gas and its effect on fuel system parts, I don't know what else to suggest other than cleaning the injectors and making sure the battery you use is fully charged as you want the engine to turn as fast as possible.
One last thing is that the rings may be stuck after sitting which makes compression low. You could test compression, but you would have to take the oil pan off and drop the crank as there is not any cleaner I can think of that would not pose a threat to harming the cylinders. At least you would know if it is part of the issue.
Let me know how things turn out.