I am checking to see what may be causing my cmc speedster’s fuel gauge to read empty when ignition is off and it reads full all the time when I turn on the ignition. I have replaced the sending unit and replaced the gauge with a used replacement. Any suggestions would be appreciated.
Renfrance
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could the tank be full
My needle first moves below Full when there's 4 gallon of gas left in the tank. I'm running a 12.5 gallon tank and have bent the arm on the float to get more sensitivity at as it empties.
Just another data point.
The fuel gauge on our cars suck. It's a waste of space on our dashboards.
Just go by distance. When you fill up next time, zero out your odometer, and go until you run out, and record this number. That'll be your gauge from now on. Just remember, never zero out your odometer while moving. It'll break, then you'll really have no way of knowing.
City driving 100 miles fill it up. Hwy driving 150 miles fill it up. Forget the gauges, they are worthless.
I am beginning to agree with that philosophy.
Fuel gauge in the Spyder is pretty good. Def wobbles some with the waves in the tank, but full from 1/2 is like 5.5 gallons and full from a 1/4 reading is like 8.2 gallons. So I take that to mean it'll be empty when it reads empty. It's a repop Bug sender in the stock location, with Gordon's "5-Cent Racing" needle-calmer-downer gizmo wired in.
@Renfrance wrote: "my cmc speedster’s fuel gauge to read empty when ignition is off and it reads full all the time when I turn on the ignition. I have replaced the sending unit and replaced the gauge with a used replacement."
Question:
What happens when you turn on the ignition and the gauge goes to "full", then leave the ignition turned on and remove the gauge wire from the sender. Does the gauge now go to "empty"? It should. Max resistance on the sender is "empty" and least resistance is "full". When yu swapped senders, did you remember to bend the float arm 180º from the original direction because the gauge reads the sender a$$-backwards?
I'm trying to help you isolate the source of the problem. Doing that, above, will point to or isolate the sender or something else and we can go from there.
I have attached a wiring diagram (JPG and PDF) for the BACK of your CMC gauges. This may help you decide if the fuel gauge circuit is mis-wired. If the wire from the sender to the gauge is shorted to ground, somewhere, the gauge will read “full” all the time. If you pull the sender wire off of the back of the gauge and it still reads “full” then it’s a bad gauge. If it drops to empty when the sender wire is pulled off the back of the gauge, then it’s a miswired or a shorted wire from sender to gauge - Got it?
Let us know how you make out.
do the 100 mile thing,its easier....give the ol bladder a relief stop..or get another 20 ouncer to go
