I've got a 72 ES with fuel problems. My mechanic thinks it might be a corroded pick up line in the tank but we recently replaced the fuel sending unit and the tank is nearly spotless, including the brass filter at the bottom so I don't think that's the cause.

The car runs perfectly on a full tank until I use about 15-20 litres (4-5 gallons) of gas, then it runs like air is getting in the system or as though only pulses of fuel are getting to the injectors. The more I try to run it with less than 2/3 of a tank, the worse it runs. This happens with every tank of gas for the last year.

The only exception to this rule occurs when I have a full tank of gas but the engine is very hot. For example, I recently drove about 100 km (60 miles) out of town and filled up before I left. The car ran perfectly for the first 45 minutes then started hesitating intermittently. It's like the fuel supply goes off for a second, on for a second, but surprisingly the car almost never stalls. In this case, I pulled over and let the car cool down for 10 minutes and it ran perfectly the rest of the way.

To summarize - the car runs like crap with less than 2/3 of a tank or when it is very hot. Any suggestions?