1979-1993 & 94 Conv [Subscribe to Daily Digest] |
Hi Mel,
actually the fuel pump and main pump work like this (see link below for picture), the main pump is attached to the internal fuel plumping and to power, the main pump resides inside and almost centered in a can slightly smaller that a 1 lb coffee can, it draws fuel from *inside* that can. The pre-pump, wired in parallel with the main pump (meaning it runs all the time) has an attachment that sits very near the bottom of the fuel tank and scavanges fuel from there ALL the time, not just when it's low, and pushes fuel directly out it's top into the 1 lb coffee can where the main pump is doing it's thing. When, and if, the pre pump stops working, the only way that the coffee canister with main pump gets any fuel to work with is gravity feed into that canister. It does have a couple of places that fuel can "leak" into the canister. so, when the fuel is higher than some point on the canister it leaks into the canister, the main pump is happy, UNLESS 1) your demands on fuel flow exceed the gravity flow into the canister, or 2) the main pump is weak already, and 3) the one we usually hear about, the level of fuel in the tank is low enough (some magic point) that the fuel is not leaking into the canister. think going around corners, extended curves, uphills and downhils. Usual symptom is you are running out of gas, observed and not via the gauge, and you can only put about 12 gallons of gas in the 16.1 gallon tank. The pump is not scraping the bottom of the barrel! Also, when the prepump and/or main pump are replaced there are both depth adjustments and direction on the compass of the pump and there are differences by year, nice write up in the Bentley on this.
If you get the pump out, take the prepump off, pretty easy, and put 12v to it briefly, remember the sound. if you got a replacement motor do the same and compare.
http://www.saabnet.com/tsn/members/gallery.html?memberID=5953&do=show&id=12326
, Tue, 9 Sep 2008 19:00:50, Mon, 8 Sep 2008 03:49:10
, Sat, 6 Sep 2008 05:56:22, Sat, 6 Sep 2008 20:13:30, Sun, 7 Sep 2008 08:05:58
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