Hello. Been a while. About 3 months ago my 30 year old fuel age got a mind of its own and started doing all sorts of weird things. I over filled the tank in the 100 degree GA heat in the Summer. The gauge went past the full mark. After about 150 miles later it came back down to 3/4 of a tank and worked fine. I don't drive her very much so it was about 2 months later I needed gas. I only pumped about 15 gallons in effort to avoid the same hang up issue. I got gas again last week and I only pumped 10 gallons in the tank from about 1/4 a tank. Now the gauge has went up passed full again. Any ideas what is causing this. I've heard sending unit, too much pressure in the tank at fill up, a sticking float or bad gauge. Thank you.
Thanks Pete D. Yep, I'm guessing it is the IVR. Yesterday I noticed the temp and op gauge were nearly at HOT. I always keep an eye on these during normal city driving. When I would come to stop they would fall back to normal-gradually at idle for 5 or so minutes. Still having fuel gauge issues too. Do these IVR's go out a once or is it a gradual thing. I've been having these issues since August. Yesterday was the 1st time for the temp and op gauge. Thank you.
Those mechanical IVRs are a legacy from the 1960s or even earlier. They are a primitive mechanical version of PWM control where a bimetallic strip that conducts the current that go to the gauges opens and closes a circuit once every second or so to regulate the average voltage applied to the gauges to 5 Volts. The bimetallic strips contacts stick shut, causing the gauges to receive more voltage making them go up. Eventually the contacts unstick on their own, and sometimes a good swat to the dash can unstick the contacts.
New mechanical IVRs arent cheap and will fail again due to their ancient design. I built myself solid state versions years go for my older Fords that last forever. I think you can find solid state IVRs online (Ebay, etc) for Fords for 1/3 the price of the POS mechanical ones and they will last the life of the car.
Jeff Korn
88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
11 Crown Vic Interceptor
14 Toyota Camry (wifes car)
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized