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A good one here! Came it with a no start..... Found not a drop of gas in tank, gage reads 3/4.... Faulty gage right? wrong! tested the gage, tested wiring, simple: gage gives resistance to cluster directly, gage is spot on!!! tested wiring for short, bad contact, gren crustys! name it! back probed at cluster unpluged, within spesc! so everything from gage to cluster is mint! cluster reports the right amount of fuel level in tank but never moves.... even after 1000 miles.... the only way it can read the right level of fuel, is if i unplug the cluster for a couple of seconds.....after that it reads ok but keeps that level in memory..... any thaughts? buy the way, already replaced the cluster!!!!! still acting up!!!!! Dont like to change parts!!!!
So let me get this straight - If the tank is 1/2 full, and you plug the cluster in, it'll read 1/2, right? If I were to then suck the tank dry, the gauge would never move from 1/2 full? Then, cycle the cluster connector, and it'd show empty?
How about a variable resistor in place of the fuel level sender? If you were to vary the resistance of that circuit manually, would the gauge respond?
I seem to recall some vehicles came with a gauge that maintains its reading with the key off. It seems like when the gauge received power it was free to move and when the key was off the lack of power caused it to maintain the reading. This is from my hazy memory from seeing one years ago as a kid and wondering how it worked.
Hi..
The first thing I would do is look at a wiring diagram for the sending unit / pump. Next I would look to see any common connections that are associated with this circuit.. If there is a relay I would test the control side and the load side.
You say that you unplug it and re plug it and it works, I would think I look at some kind of control side. Check your wire diagram for all common grounds as well. Don’t for get to check any relays!
Just like numerous posts have already indicated, determine where the cluster gets the ignition on signal. Once found, ensure cluster is receiving ignition on.
I would assume overall powers and grounds would be good since you didn't indicate any other cluster issues, but I have been wrong many times before. You know what happens when you assume. LOL
Somehow the gauge does not know when to hold a value and when to allow it to change.
I like the idea of using a variable resistor or use a variety of resistors to check signal integrity and gauge response. But, from what you have said, it appears to be a gauge issue.
Thank you all for your inputs.... I did do my homework before posting... the variable resistor idea is what i did.... whit the sender removed from the tank with a multimeter attached to it to see the values real time.... the sender is spot on.... the cluster never reacted to the change in level.... unless i unplug it and replug it.... Did all the basic wiring checks also....
do you have a scanner that can do a gauge sweep test? also does the pcm receive the value from the sending unit then it sends it to the cluster over the network?
Yes, i have a scanner/scope... Verus pro.... No sweep test available for this vehicule, only the factory scan tool can access it.... The gage in the cluster works.... can make it report the actual value but only if i unplug the cluster and plug it back in..... The pcm is not involved in reporting fuel level... sender goes directly to cluster via variable resistor...
JeffBirt wrote: I seem to recall some vehicles came with a gauge that maintains its reading with the key off. It seems like when the gauge received power it was free to move and when the key was off the lack of power caused it to maintain the reading. This is from my hazy memory from seeing one years ago as a kid and wondering how it worked.
This kind of reminds me of when the tank is filled with the key on, but it doesn't register until the key is cycled.
What happens if you disconnect the sender at the tank and reconnect it? The gauge should go to empty with the tank sender unplugged, I'm curious to see if it goes back to the incorrect value, reports the correct level, or doesn't move at all.
The system looks about as basic as they come, weird issue... :blink:
tried the plug unplug thing with the sender......no change untill i unplug the cluster and plug it back in... for example: key on, gage reads 1/2... actual level in tank.... unplug sender with the key still on.....gage still at 1/2..... key off and remove key, with gage unpluged.... insert key an turn on... still 1/2.... unplug cluster and replug it gage reads empty(as it should).....
Unfortunately, I tried to zoom in on your uploaded diagram and just can't get the detail I need.
When you say you unplug it, where are your unplugging it? At pump or behind fuel gauge?
In the past, I do remember someone telling me their is circuitry present to not make the needle bounce as you drive, caused by fuel moving around in tank as we drive. How does this car handle this?
Again, maybe it is real obvious via the diagram, but I cannot make it out. Sorry if this is the case. I know you have done your homework.
The unplug it part: I unplug the connector at the back of the cluster 40pin connector.... Sorry for the diagram... will try to upload it in two parts....
For the bouncy needle, i assume the cluster takes readings every time or so to ajust for the fuel level decreasing.... but on this one the customer went for a 300km trip and the gage never moved.... talk about fuel economy!!!! lol!!! And thanks for all your inputs!
The problem maybe internal in the cluster, such as the servo or a loose or worn contact. From my understanding you've checked from the sending unit to the cluster with all test passing. If that's the case your attention next maybe the cluster. Chevrolet is famous for having a series of bad clusters. I always check from point to point in a methodical manner, not doubting my results until I'm at the of ther end and fully finished. You've gone from the float to the the back of the cluster now check to the needle!
ephotrod wrote: The problem maybe internal in the cluster, such as the servo or a loose or worn contact. From my understanding you've checked from the sending unit to the cluster with all test passing. If that's the case your attention next maybe the cluster. Chevrolet is famous for having a series of bad clusters. I always check from point to point in a methodical manner, not doubting my results until I'm at the of ther end and fully finished. You've gone from the float to the the back of the cluster now check to the needle!
As i mentionned, the cluster also was replaced.... Based on all the other tests.... Same problem.....
Kirby wrote: The unplug it part: I unplug the connector at the back of the cluster 40pin connector.... Sorry for the diagram... will try to upload it in two parts....
For the bouncy needle, i assume the cluster takes readings every time or so to ajust for the fuel level decreasing.... but on this one the customer went for a 300km trip and the gage never moved.... talk about fuel economy!!!! lol!!! And thanks for all your inputs!
Maybe you're onto something here... How DOES the cluster decide when to move the needle? :huh: No modern gauge is directly tied to it's sensor input, otherwise it'd be swinging all over the place, so there has to be some logic involved.
Some input to the cluster is missing? Something to clue it in that, "Hey, the vehicle is moving, keep an eye on the fuel level." Have you already gone over powers and grounds at the cluster?
the variable resistor idea is what i did.... whit the sender removed from the tank with a multimeter attached to it to see the values real time.... the sender is spot on.... the cluster never reacted to the change in level.... unless i unplug it and replug it.... Did all the basic wiring checks also....
