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Old 06-05-2013, 09:59 PM
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GM Fuel Tank

1992 Chevy Silverado. Removed the bed and the fuel pump to inspect inside the tank with the idea of cleaning it out since the truck sat two years. In the tank there are baffles that sit quite a ways from the bottom of the tank itself. I'm thinking these are anti slosh baffles.
It appears they're held in place by 4 studs, issue is there are cracks coming off each hole where the studs ride. What kind of issues will the cracks cause? The fuel pump sock rides in the top baffle but since it sits so far above the bottom of the tank how does it get fuel in the baffle once the fuel level is below it? from slosh? My father's 98 GMC 1500 has no baffles in the tank and the fuel pump sock rides on the bottom, this seems like a lot better idea as in my opinion having a baffle that sits above the bottom of the tank is a rather dumb idea. I'm also thinking the cracks would cause the fuel in the baffle to drip out when at a dead stop and would cause the vehicle to shut off or the fuel pressure to become erratic. I don't think trying to epoxy the cracks would do much good and the baffles won't come out without breaking them so it looks like a new tank is in order. Can anyone shed some light on why GM used this design then dumped it later? Or if there is a possible fix for mine? Any help is appreciated.

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Old 06-06-2013, 03:44 AM
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Quote:
Originally Posted by DoubleVision View Post
1992 Chevy Silverado. Removed the bed and the fuel pump to inspect inside the tank with the idea of cleaning it out since the truck sat two years. In the tank there are baffles that sit quite a ways from the bottom of the tank itself. I'm thinking these are anti slosh baffles.
It appears they're held in place by 4 studs, issue is there are cracks coming off each hole where the studs ride. What kind of issues will the cracks cause? The fuel pump sock rides in the top baffle but since it sits so far above the bottom of the tank how does it get fuel in the baffle once the fuel level is below it? from slosh? My father's 98 GMC 1500 has no baffles in the tank and the fuel pump sock rides on the bottom, this seems like a lot better idea as in my opinion having a baffle that sits above the bottom of the tank is a rather dumb idea. I'm also thinking the cracks would cause the fuel in the baffle to drip out when at a dead stop and would cause the vehicle to shut off or the fuel pressure to become erratic. I don't think trying to epoxy the cracks would do much good and the baffles won't come out without breaking them so it looks like a new tank is in order. Can anyone shed some light on why GM used this design then dumped it later? Or if there is a possible fix for mine? Any help is appreciated.
I'm sure you're smarter than g.m. but my guess is that running the sock away from the floor keeps it clean from the junk that gets in the tank. as for the baffles, I'd guess they are there to keep the sloshing of fuel from upsetting the entry of the fuel at the sock but thats just my guess, as plugged up socks kill pumps,
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Old 06-06-2013, 08:13 AM
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The 1998+ trucks use a jet pump which fills the fuel pickup chamber. These fuel sending units are differnt than the 1997 and older setups.

pics

1997 and back fuel sending unit


1998+fuel sending unit-


In teh 1998 unit the fuel is picked up from the tank through that sock, then some fuel is diverted into that big white plastic "cup" that encircles the sending unit. While some of it is sent to the engine.
When fuel is low in the tank and under times of fuel slosh and the fuel sock runs dry temporarily, fuel is then immediatley taken from teh white plastic cup until fuel surrounds teh fuel sock again.

I have a few 1997 and 1998 Vortec 350 trucks. When I am under 1/4 tank, if I satnd on teh throttle form a dead stop in the 1997 trucks, teh fuel wish slosh and the engine will bog HARD. The 1998 trucks wont do this.

Basically instead of using the baffled tank, GM made the cheaper unbaffled tanks and simply changed the fuel pump design.

The 1997 and older pumps use the threaded suppy and return lines, while the 1998+ pumps use the quick-connect fittings. Both fuel sending units are of different diameters and cannot be interchanged.
The 1998 sending units are held down into teh tank by a snap ring, whereas the 1997 and older units are held down by that cam type ring that you turn by using a hammer tapping on a screwdriver to turn the cam-lock device.

peace
Hog
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