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So, this took a while, but it's done and it is humming beautifully.
One question I had, which I may have answered, is if it's the pre-pump that generally is the bad pump. The car ran just fine due to the main Bosch pump, likely, but the noise was incredible.
Initially, I installed a hand-me-down used pre-pump. This pump was supposedly a "known good" but it was loose within the housing a little bit so I was suspecting something wasn't quite right. Upon removing the old pump, there was metal dust in both the tank and on the filter that connects to the bottom of the pre-pump. I think that's bad (ya think?), so I decided at least that was bad. Once installed, the used pre-pump sound was different but not exactly reassuring. I now had a hum that would change abruptly. Kind of a HUMMMMMMM, hum, hum, HUMMMMM oscillating. But at least it wasn't ratcheting. Still, I never had any stalling problems.
Finally, the new AC Delco (Made in UK) pump came and it was identical to the other two used pre-pumps and it fit exactly. By the way, at least from what I can tell, black wire goes to the left, white to the right, or that's how I see it on all the used pumps on the Internet. I decided at that point to just go full out and replace the main Bosch pump with the new one. With both new pumps installed, it hums beautifully with no oscillation and no ratcheting. I will keep the old Bosch main pump as a spare since I now think that what I have read elsewhere must be true: generally it is the pre-pump that should be suspect and a lot of the main Bosch pumps are needlessly replaced.
BTW, the correct pre-pump is AC Delco p/n 6441336 or at least it's identical to the pump I had and it fits. Some in this forum had mentioned that their pre-pumps were too long. The new pump is identical and still made in the UK and says AC Delco on it.
posted by 24.118.5...
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