Hi Bruce,

Yes, I took a look at this. But I don't know for certain from experience the tank pump on a Bosch system for a 900 is the same as those from the 200 series.

On the 200's tank pump, an AC Delco design and OEM, the impeller is centrifugal, meaning the intake is to the center of the impeller and the output taken from the outside. The pins are marked + and - by being cast in the molding.

The impeller's port is shaped to be efficient with only one polarity, but it definitely will not draw fuel from the output and spit it out the intake if wired backwards. A new pump would not have a problem with reverse rotation, but a used one with brushes worn, will have taken a set in the brush position and not run smoothly and freely backward.

The reason I spent time to check this out came from trying to help a friend, long distance, just like we are today. He had gone through two new replacement pumps with early failure, and I had suspected perhaps the wiring had gotten flipped around. The third replacement pump was a pay-through-the-nose blue-boxed version from the Volvo parts counter. Installing that was the last trip into the tank for him. Beats me what the trouble was with the other two pumps - I all but begged to have them for post mortem, like done with these originals.








--
Art Benstein near Baltimore

Today's mighty oak is just yesterday's nut that held its ground.