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September 1990
Dear Tom and Ray:
I have a 1981 Volvo DL with a humming fuel pump. From inside, it sounds like a hum, from outside it sounds like a buzz. The hum/buzz gets louder when the gas tank gets below 1/2 full. My husband called our repair shop and they said this was pretty normal. Is it?
Pam
RAY: Unfortunately, yes. Your car has two fuel pumps. It has a "pre-pump" inside the gas tank itself, and a regular fuel pump outside the tank. Most likely, the pre-pump is no longer working. What you hear is the regular pump straining to do the work of both. It has to work harder as the tank gets emptier. That's why it gets louder. You need to replace the pre-pump before the regular pump dies from exhaustion.
TOM: This question once again illustrates a profound difference between my brother and me. My brother always wants everything to run perfectly...he's bothered by the slightest imperfection. Me--I always try to make the best of the situation. I wouldn't fix it if I were you, Pam. What you've got is a unique low fuel warning system. When you hear it hum, that just means it's time to fill up the tank! Back to the September 1990 index
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© 2006 by Tom and Ray Magliozzi and Doug Berman. Distributed by King Features Syndicate, Inc.
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