Quirky fuel gauge needle - Forums at Modded Mustangs
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post #1 of 3 Old October 29th, 2019, 06:29 PM Thread Starter
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Quirky fuel gauge needle

Just curious if this is the norm for these cars or not.

Since I've owned the car (about 11 years) this has always been the case. With a full tank of gas the gauge moves very slowly, almost not at all, over the course of 3-4 days then over the next 3-4 days they gauge goes from full-ish to empty. These days are my average and change based on how/where I'm driving, but basically the gauge moves really slowly at first then rather quickly after that.

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post #2 of 3 Old October 30th, 2019, 12:58 AM
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My 04 has a similar issue. Its a garage car for the past three years. Since i got a 04 GT five years ago and slammed the left headlight into the back of a lady that decided to stop on the highway for “a speedbump”. I picked up this convertible and did a GT swap (complete interior and driveline) and just this summer the same thing. My needle registers full then I park it for a week and says it empty. Drive it around a few sharp corners or a short stop and burn. Then it’ll slowly come back to correct reading ( only what can be guesstimated) I have another sending unit that came from my original GT but just haven’t had the will to do it. Not to steal the convo but can anyone tell me what my fuel system looses prime? After two to four days not running it i have to squirt starter fluid and its fine but after sittin for a few days same stuff...
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post #3 of 3 Old October 30th, 2019, 09:03 AM
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Regarding the needle it could be either something to do with the sender, like the resistor failing, bent float arm, or failed float, or even with the gauge cluster.

For the losing prime, you could have a bad/stuck PPRV valve, or a slight leak in the system. I would get a pressure gauge on the rail and see what it does with key on. Does the pressure jump up to 39psi? If not, it would go back to a fuel pump issue. If it does then rapidly decay, then it's a PPRV or leak.
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