North American Turbocoupe Organization



Low fuel light always on
matiii1 Offline
Member
#1
I have 87 Tbird and for about a year the low fuel light stays on about 95 percent of the time but does go out on occasions.I know i have at least half tank full most of the time.The fuel gauge reads about where it should.Is the sensor for this light on the fuel pump/sending unit or is it somewhere in the fuel line upstream from the tank.Any help would be appreciated.
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John B Offline
Member
#2
Sounds like an issue with the sending unit which is located in the tank. Has the tank ever been dropped/replaced in your car? You can also check the wires going from the sending unit to your gauge. This would ensure that there isn't something wrong with the wires.
88 Turbo Coupe: Front mount intercooler, MGW short throw shifter, full coilover conversion, tubular control arms front and rear, svo front brakes, vacuum assist brake swap, manual steering swap, GT35R turbo with external gate, pimpx ecu, 60lb injectors, 3 core aluminum radiator, Boport 1.5 cam, gutted upper, corbeau fixed back seats, and the list goes on.
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vegas_ss Offline
Senior Member
#3
There is a module by the glovebox ( between the glovebox and upper kick panel) that has a touchy ground, sometimes wiggling the wire bundle helps, haven't really checked it out, my low fuel light usually comes on around 1/3 - 1/2 tank but goes off within a few minutes.
1987 TC, 5sp, Boport Stage 3 Head/2.1 Cam
1996 Impala SS, DCM, Borla Cat Back, too much other stuff!!! (SOLD)
2009 Pontiac G8 GXP 6M, 6.2l LS3, Kooks Long Tube, Hi Flo Cats, Mild Cam
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BigJake Offline
Member
#4
Years ago I replaced my fuel pump and I think the low fuel light had it's own switch ? Wish I could remember.
1987 Thunderbird Turbo Coupe 5 speed Boosting 25 PSI with Boport/Stinger parts !
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vegas_ss Offline
Senior Member
#5
Here is the info from Jeff I was referencing

LFW isn't a separate sensor in the tank. LFW module just reads voltage across the fuel gauge (slightly more complex than that, but close), and turns on the LFW light when voltage drops below a given value. If the fuel gauge works correctly, the problem is in the harness or the LFW module. CHeck the 5 pin connector on the LFW module for looseness, corroded pins, etc. LFW module is a black box to the right of the glove box, with connector pointing down.

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Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 23 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 04 Taurus Duratec (wifes car) // 91 Topaz (daughters first car)
Jeff Korn
1987 TC, 5sp, Boport Stage 3 Head/2.1 Cam
1996 Impala SS, DCM, Borla Cat Back, too much other stuff!!! (SOLD)
2009 Pontiac G8 GXP 6M, 6.2l LS3, Kooks Long Tube, Hi Flo Cats, Mild Cam
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matiii1 Offline
Member
#6
Thanks for the replies.Im going to check out this stuff near the glove box first and see if I find anything.
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BigJake Offline
Member
#7
Found a YouTube video and the fuel level sending unit has it's own hole and the fuel pump pump has it's own too. Getting old is tough LOL.
1987 Thunderbird Turbo Coupe 5 speed Boosting 25 PSI with Boport/Stinger parts !
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anasazi4st Offline
Senior Member
#8
(07-21-2023, 11:29 PM)BigJake Wrote: Found a YouTube video and the fuel level sending unit has it's own hole and the fuel pump pump has it's own too. Getting old is tough LOL.

That didn’t help me. As vegas_ss suggested, the Low Fuel Module is next to the glove box on the right—mine is light orange in color, about the size of a tape measure, but not as thick. It plugs into a connector there. I’ve tried several and some have worked (for a while), some have not.

I understand you, like me, probably want everything to work like it did when it rolled off the assembly line. This is one where you need to choose your battles. I’ve found that it’s not a good idea to let the fuel get much below the halfway mark. I wish there was a way to simply drain the tank without removing it. There’s probably (at least in mine) a whole lotta junk at the bottom of that tank that shouldn’t be there. Once when the car was down for a tranny rebuild or something I let the fuel get too low and MAN did it run like CRAP for a while. I’ve heard it’s REALLY not good for the fuel injectors to allow it to get it down too low, probably because of all the junk like water that gets through the “sock” in the tank and the fuel filter.

So, in my case at least—no. Check that Low Fuel Module first before you start tearing things apart.
Another proud dues-paying member.

1987 Turbo Coupe w/T5OD, 8.8 axle, grey smoke; most options. Got it in 1991 with 41K miles: 3 turbos, 2 heater cores, 3 T5OD full rebuilds, 6 clutches, 1 head gasket, 2 Teves II ABS units, etc. later....
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