Mazda 626 2.0L 1996 - Starving for Gas

Interesting, I would have started with the fuel filter, instead of the pump. I'm guessing its Fuel injected? in tank pump? not really familiar with the 626's

The car seems to run better on a quarter tank of gas, than when it has a half tank of gas or more. -Thats a bit interesting to me, but there is a first for everything, right?

I would start with your filter, move to (injectors/TB/Carb), Play (carefully) with your fuel mixtures, if all this provides no result, drop your tank and investigate.

You possibly would have a leak somewhere in your intake side of your engine (IE intake manifold/injector seats ect)

Its quite a fun little problem, i wish the best of luck to you.

It has a new fuel filter and I tried a bottle of Prestone fuel injector and intake valve cleaner. When my mechanic changed the fuel pump out he check the fuel filter to see if the fuel looked dirty. He said it looked clean.

I asked my next door neighbor what the problem was. He's a mechanic for Volkswagon.

It was the Mass Air Flow device. Did not replace MAF simply cleaned it with brake cleaner then sprayed dry with a can of air. Car has more get up and go now than some small V6 cars. Ben explained that the sensor wires get oil build up on them which throws the readings off of the MAF.

It has long passed the guessing time. Put a pressure gauge on the thing, drive it till the problem is present. look at the fuel pressure. If it is within specs, you almost certainly are not starving for fuel. A restrictive catalytic converter, or exhaust system anywhere can feel like fuel starvation. The test for this is a vacuum gauge. When driving, when you reach the limits of exhaust flow, the engine vacuum will drop off very rapidly. Under hard use, it will go to pressure. TEST. TEST. TEST.

Check the return venting of the tank.

Did you check the air vent to the fuel tank? as it could be the pump making a vacume in the tank and then u get engine starvation. And is it engine starving or flooding the problem? did you check your fuel pressure from the pump ? There could be sediment but cant see why it works better with a quarter of the tank than a half tank (if there is sediment it should be even worse when its quarter full!

If there was sediment in the tank, it would clog your fuel filter. If there is sediment in your tank, it will be at the bottom of the tank. The fuel pickup is always on the bottom of the tank. It will suck the sediment first, them clean fuel when the sediment is gone. TEST.