Hello. I am new to this board, so I thank everyone in advance for any help they may give.

Here are the problems with my 1988 245:

After driving about 15 km with no problems, I experience this phenomena:

When I engange the clutch and depress the accelerator pedal, the vehicle accelerates momentarily, then becomes un-responsive to the accelerator. The engine is running smoothly, with-out misfire, just un-responive to my
attempt to accelerate. If I shift to 2nd gear, same deal--momentary response followed by a loss of responsivenessto my depressing the accelerator. Same with 3rd gear. Vehicle idles mint. The vehicle still moves in 1st and 2nd grears without problems, so I can limp home.

Concurrent to this problem:

The wagon has become increasingly difficult to start when the fuel in the tank drops below rougly 1/4 of a full tank. I don't know how long this my have been occuring, because i have some sort of phobia about a tank that is less than 1/2 full-but i've been driving longer distances lately. Having read archived messages on this board, I believe this may be a problem with the in-tank fuel pre-pump or a defective pump signal relay (switch).

Where can I start with diagnoses? Are these problems possibly related?
I can supply more detail if needed.

Just to give you an idea about myself and my abilities, I usually try to do my own work when the problem is obvious. I can do most remove and replacement tasks, such as water pump, alternator, springs, shocks, etc. I can do minor service (cap, rotor, timing belt, plugs, filters, etc.). I have a multimeter, but don't know how to use it. I just don't know how to find the source of unobvious problems

Thanks again for your help.