Is the tank the same or not and how about the fuel pickup lines in the tank?

I recently replaced my fried sending unit with an 87 Tpi unit. Today when i took the sharp right turn the engine cut out like the fuel pump wasn't picking up and the gauge showed very close to empty. So i filled up and i only put in 41 liters of gas.

That would indicate that there was still 20 liters left. (4 gallons).

My question again is:

- could the tank be different shape or depth and the fuel pick up in too short

- and does it matter which way the filter at the bottom of the fuel pump is located

Any suggestions welcome.

 

Looked at a couple senders from different years, all look the same. There is a tab that locks in the sending unit, can't get it in wrong that I know of. Not sure if there is a different tank size, could be. Odd shaped tank but the lower section is smaller so you shouldn't get the loss of suction with four gallons still in it I'd think. My 88 doesn't hold very much gas for sure, Fill up when near empty is about 10 gallons. Guessing a 14 gallon tank. Kind of unhandy to fill up so often but I get decent gas mileage so I'm not complaining.