Fuel Gauge bounce

[Bitsyncmaster]

I was driving home yesterday on some pretty ruff roads and saw my fuel gauge would bounce around instantly and get stuck at the vertical (way past full) position. At the end of my trip the gauge is working fine. I have the Zilla fuel gauge unit and there most likely is an intermittent connection but I would have though the gauge itself would have some dampening built into the mechanics.

Has anybody ever seen their fuel gauge jump instantaneously like that?

I did have it get stuck at that vertical position once a long time ago. Just wondering if I should buy a new fuel gauge.

[DMC5180]

Bad connection someplace for sure. None of the tube style fuel senders have built in buffering. If the Needle pegs straight up you momentary lost the input signal. I could easily see the DMCH original replacement senders jump between steps.

[David T]

I have a Tankzilla also. I was getting some erratic readings. Solved it by taking the sender unit out of the tank and cleaning the long wire with some sandpaper.

[Delorean3610]

My fuel gauge needle started pointing straight up on Saturday. What caused your issue?

[dmruschell]

I was driving home yesterday on some pretty ruff roads and saw my fuel gauge would bounce around instantly and get stuck at the vertical (way past full) position. At the end of my trip the gauge is working fine. I have the Zilla fuel gauge unit and there most likely is an intermittent connection but I would have though the gauge itself would have some dampening built into the mechanics.

Has anybody ever seen their fuel gauge jump instantaneously like that?

I did have it get stuck at that vertical position once a long time ago. Just wondering if I should buy a new fuel gauge.

I had this exact issue a couple of months ago. I cleaned off the contacts where the fuel sender connects to the car harness. That fixed the gauge issue.

However, the next time I went to start the car, I realized that the fuel pump wasn't working. Apparently that connection was corroded, too, and I had nudged it just enough to break the connection, so you might as well clean that connection too while you're in there.

[TTait]

None of the tube style fuel senders have built in buffering.

The DMCH reproduction senders (which never show full) can buffer a bit, physically. There are two screws in the bottom of the unit, used to hold it together. Some units seem to be virtually fuel tight at the bottom and don't appear to work, or can take hours to show that you have added fuel to the tank ,or hold the sender full of fuel higher than the level in the tank. With those units I was told that if you loosen one or both screws a bit, you can adjust how much fuel seeps in and out of the bottom of the unit, and therefore adjust its sensitivity. I've had to adjust 3 units like this over the years.

IF you had a DMCH unit I'd suggest you tighten one or both of the screws just a bit... You can look at the tankzilla and see if there is any method of adjustment in the bottom of your sender.

I hoped for years that Houston would build a better unit, but now that they have their all in one - little chance of that. My advice is to try to keep the Zilla unit working as the DMCH ones are not the greatest (with each unit I've seen they never register a full tank it drops down almost instantly - either something is restricted inside the housing or the switches near the top of travel are poorly implemented.)

T

[Josh]

The DMCH reproduction senders (which never show full) can buffer a bit, physically. There are two screws in the bottom of the unit, used to hold it together. Some units seem to be virtually fuel tight at the bottom and don't appear to work, or can take hours to show that you have added fuel to the tank ,or hold the sender full of fuel higher than the level in the tank. With those units I was told that if you loosen one or both screws a bit, you can adjust how much fuel seeps in and out of the bottom of the unit, and therefore adjust its sensitivity. I've had to adjust 3 units like this over the years.

IF you had a DMCH unit I'd suggest you tighten one or both of the screws just a bit... You can look at the tankzilla and see if there is any method of adjustment in the bottom of your sender.

I hoped for years that Houston would build a better unit, but now that they have their all in one - little chance of that. My advice is to try to keep the Zilla unit working as the DMCH ones are not the greatest (with each unit I've seen they never register a full tank it drops down almost instantly - either something is restricted inside the housing or the switches near the top of travel are poorly implemented.)

T

My Dmch combo sender/fp registers full consistently. I do find it sits at each tick for a while but drops very quickly between ticks. 4/4, 3/4, 1/2, 1/4

[DMCMW Dave]

I've noticed that there is damping in the gauge itself. On most cars. Once in a great while I see a car where the gauge in the dash is completely undamped. When combined with the aftermarket sender the movement is very jerky, you can see where the float passes the reed switches. I'm not sure whether this is a difference between gauges or a repairable defect, I've never dug into one to find out.

The new all-in-one unit is VERY heavily damped in the electronics, on the order of minutes. On purpose. The only time you'll ever notice it, is if you fill the tank with the engine running. But you'll never see the gauge wandering around as you speed up and slow down.

FYI on the original post - here's a quick check of the car/wiring - if the sender is disconnected or broken internally, the dash gauge will point straight up. On the wiring at the sender there are three wires. One is black. Ground the other ones to the black one, one will turn the "empty" light on and the other will make the gauge point straight down (sorry - don't recall the colors offhand).

[dmruschell]

I've noticed that there is damping in the gauge itself. On most cars. Once in a great while I see a car where the gauge in the dash is completely undamped. When combined with the aftermarket sender the movement is very jerky, you can see where the float passes the reed switches. I'm not sure whether this is a difference between gauges or a repairable defect, I've never dug into one to find out.

The new all-in-one unit is VERY heavily damped in the electronics, on the order of minutes. On purpose. The only time you'll ever notice it, is if you fill the tank with the engine running. But you'll never see the gauge wandering around as you speed up and slow down.

FYI on the original post - here's a quick check of the car/wiring - if the sender is disconnected or broken internally, the dash gauge will point straight up. On the wiring at the sender there are three wires. One is black. Ground the other ones to the black one, one will turn the "empty" light on and the other will make the gauge point straight down (sorry - don't recall the colors offhand).

A friend if mine owns a late 1000s vin DeLorean where every needle on the dash jerks around. It's as if there is a digital meter driving the analog needles because the motion isn't smooth on any on the four smaller gauges. Were going to be overhauling his car this winter and was wondering if there is any way to fix the needle jumping, or if that's normal on some cars.

Sorry for the hopefully short hijack.

[DMCMW Dave]

A friend if mine owns a late 1000s vin DeLorean where every needle on the dash jerks around. It's as if there is a digital meter driving the analog needles because the motion isn't smooth on any on the four smaller gauges. Were going to be overhauling his car this winter and was wondering if there is any way to fix the needle jumping, or if that's normal on some cars.

Sorry for the hopefully short hijack.

I have not see this on anything but the fuel gauge. "Check your Grounds"

[dmruschell]

I have not see this on anything but the fuel gauge. "Check your Grounds"

Yeah, I think his grounds need going through anyways based on other things his car does. Thanks!

[Bitsyncmaster]

I found out if you have the tankzilla unit, if a fuel sender connection is open, the gauge will show empty. Now if there is a break in the OEM 3 pin connector (Where the OEM gauge plugged into) then the gauge points straight up. So my problem had to be an intermittent on that 3 pin circuit. I installed 3 new female pins in the connector (they were very corroded). The male pins looked good (think I pulled them before and cleaned them).

So now if that straight up gauge problem happens again.....it may be at the washer bottle connectors.

[Delorean Industries]

That is where I would look Dave. I'm curious about the tank zilla unit. I am dissolving one currently to see the inner workings since Zilla doesn't support this community currently.

[Bitsyncmaster]

That is where I would look Dave. I'm curious about the tank zilla unit. I am dissolving one currently to see the inner workings since Zilla doesn't support this community currently.

Let us know what you find. I'll bet it is just an op-amp, a few resistors and a few capacitors. The Zilla unit has a pretty large time constant (filter). It takes about 60 seconds for the gauge to settle. Don't know why the Zilla box is so large for those few components. I would use a micro to filter and calibrate if I were designing one.