I fill up my gas tank, & it shows full. Then, after I drive off the indicator shows 7/8 full. ??

Is the sending unit faulty?

I noticed when the indicator is almost to E, that the van quits running (out of gas). Usually, there is a few gallons of gas left when the indicator is in this position. Is the fuel indicator also faulty at the low-end?

 

The fuel sending unit is resistance based. so either the sending unit or the head may be bad. Since you don't say what year you have, it is a bit trickier, but you can look for a 6 connector plug just before the harness goes into the A-Pillar(inside the dash, or along the back edge of the front seat. '87 and older have the A-Pillar plug. 89 and newer have the seat one. I've not seen an 88 so I don't know which that one has, but I'm betting the seat one. Anyway you can measure with a meter to ground the resistance of the sending unit full to empty to see what data the head is seeing. There is a possibility that the sending unit sticks some. which explains the sudden drop, or the dash gauge itself may be wonky. To replace the sending unit, you need to drop the gas tank and it is really a pain in the rear end...yours and the vans'.

The other wires in the 6 position plug are rear marker lights, the dome lights, directionals and reverse. Brake lights run on a wire that doesn't go though the plug.