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Have a 1986 Olds' Cut Supreme Brougham 5.0 Liter whereas the 'fuel gauge' is stuck on full. What should I be looking for and what parts would cause this problem. All replies are appreciated.
Thanks very much. Just got the car out of the garage for repair. An 'open' circuit meaning a bad connection or fray in the wire. Seems a bit of happenstance after getting my car back from the mechanic. What would be the cost for repair should it be a bad connection? Any possibility of the problem being the sending unit?
Man, I ain't getting involved with you and your legalese. I knew you weren't going to fix it yourself. If you can't fix it yourself, you can watch your odometer or just pay the man. You're asking for a price estimate on something that a good electric guy will diagnose in 10 minutes, or a hack could fire the parts cannon at for 2 weeks. You can't estimate that, and you have a track record of picking crappy shops.
Your should sell that car.
Man, I ain't getting involved with you and your legalese. I knew you weren't going to fix it yourself. If you can't fix it yourself, you can watch your odometer or just pay the man. You're asking for a price estimate on something that a good electric guy will diagnose in 10 minutes, or a hack could fire the parts cannon at for 2 weeks. You can't estimate that, and you have a track record of picking crappy shops.
Your should sell that car.
After two to three days, the fuel gauge now reads a little above halfway. I don't know if it's accurate. At that point (being halfway), I grounded the pink wire below rear bumper and the gauge goes to "Empty". Would that be the sending unit? Actually both ends of the wire are 'pink'. I grounded each end. The 'grounding' of the male end brought the fuel gauge up to full > and the grounding of the female end brought the fuel gauge to empty.
Sending Unit Wire
Last edited by synoptic12; September 11th, 2022 at 07:32 AM.
The side that made it go empty is the gauge side, the other side is the sender. Before jumping into dropping the tank, make sure the ground wire from the sender to the body/frame is good. You should have some continuity to ground, through the sending unit, on the sending unit wire. The sender operates between 0-90 ohms.
The side that made it go empty is the gauge side, the other side is the sender. Before jumping into dropping the tank, make sure the ground wire from the sender to the body/frame is good. You should have some continuity to ground, through the sending unit, on the sending unit wire. The sender operates between 0-90 ohms.
The ground wire is pictured with red arrow. I cannot get it off. Even tried PB Blaster. The other end of the ground going to the Sending Unit is above the tank with I believe a snap on nut. I would not like to drop the tank, really am not equipped for that. I'm trying to determine if it is the fuel gauge or sending unit. The float may have gotten stuck, don't know or the resistor could be bad. As to the procedure I've conducted so far, would this be a bad sending unit? According to other replies in other forums, they state in grounding the gauge wire would bring the fuel gauge to empty. In that respect, they say it is the sending unit. How can I check for continuity if the ground wire is rusted (as shown)? Sorry for the snide remark in my last post.
Last edited by synoptic12; September 11th, 2022 at 09:03 AM.
Here is a picture of the tank (On top) whereas the ground is held in place by a push on nut. I would have to pull the tank to check that. It appears to be a sending unit. Should I replace the 'tank' as well, rather than dropping the tank months or years later for a leak? By the way, how long are fuel tanks good for? Sender Ground Wire
Grounding the Sender side at 1/2 gauge reading, 'Went to Full'. > Male End
Grounding the Gauge side at 1/2 gauge reading, 'Went to Empty'. > Female End
* When attaching the connectors (Pink) again, fuel gauge registered at 1/2 tank.
The ignition 'key' was not used at all. "THIS IS AN ERROR ON MY PART". The key was turned 'on' and off'.
Last edited by synoptic12; September 11th, 2022 at 02:51 PM.
That's odd, grounding the sender side (with it disconnected) should not have done anything with the gauge.
There has to be more to that story. It didn't do anything but since the gage side was dealing with an "open" the gage went to full anyway. The sender end had nothing to do with that. It's not Bluetooth. Although that'd be cool.
The gage probably is ok, but the sender sounds fooked. Either it's a bad connection on the sender, the rheostat is cruddy or something, or the float is sticking (this is usually a stretch but it has happened). You can take the sending unit apart and clean it, and free it up. If you don't get a new sending unit (you'll need a 3 tube, original GM part number was 25001613) then get a new retaining ring (maybe) and gasket too. if you get a new sender, it probably would come with them, but if not, you can look for GM p/n 22515965 or equivalent for the gasket, and for the cam retainer it's 25124032.
A new sender does come with a new sock regardless if it's GM or not, but if you refurbish the original sender, and you want to put on a strainer sock, you can try and find a GM p/n 5651702, aka ACDelco p/n TS1000. They're discontinued, but you may find one around. If not, find a comparable aftermarket fuel sock that fits 3/8" tube. Jeg's #78538 works, although it's just a tad longer than the GM one.
And if you pull the tank (drain it best you can first) do what you can to clean it out if it needs it. Try to reuse your old tank if possible as I'm not sure if the repro tank filler necks have been fixed to keep fuel from sloshing back out. If it's not real rusty/pitted inside or outside, you can probably reuse it. It'll just depend on condition as to how long the tanks last.
There has to be more to that story. It didn't do anything but since the gage side was dealing with an "open" the gage went to full anyway. The sender end had nothing to do with that. It's not Bluetooth. Although that'd be cool.
The gage probably is ok, but the sender sounds fooked. Either it's a bad connection on the sender, the rheostat is cruddy or something, or the float is sticking (this is usually a stretch but it has happened). You can take the sending unit apart and clean it, and free it up. If you don't get a new sending unit (you'll need a 3 tube, original GM part number was 25001613) then get a new retaining ring (maybe) and gasket too. if you get a new sender, it probably would come with them, but if not, you can look for GM p/n 22515965 or equivalent for the gasket, and for the cam retainer it's 25124032.
A new sender does come with a new sock regardless if it's GM or not, but if you refurbish the original sender, and you want to put on a strainer sock, you can try and find a GM p/n 5651702, aka ACDelco p/n TS1000. They're discontinued, but you may find one around. If not, find a comparable aftermarket fuel sock that fits 3/8" tube. Jeg's #78538 works, although it's just a tad longer than the GM one.
And if you pull the tank (drain it best you can first) do what you can to clean it out if it needs it. Try to reuse your old tank if possible as I'm not sure if the repro tank filler necks have been fixed to keep fuel from sloshing back out. If it's not real rusty/pitted inside or outside, you can probably reuse it. It'll just depend on condition as to how long the tanks last.
Thank you very much for the detailed information. However, one point yo make just does not make sense according to the steps I've taken. You state "There has to be more to that story. It didn't do anything but since the gauge side was dealing with an "open" the gauge went to full anyway". No, it did not go to full, 'It went to empty'. See Post #15
If that's what you said originally, I'd say fine. But it isn't. You said it went to empty when you grounded the gage side. Which is expected. Since it's an open with the connection apart, it's going to float to full. Once you pull the connection apart, it doesn't matter what you do to the sender side, it's not going to affect the gage. If it does, there's a new problem you'll have to deal with because electrons are going where they shouldn't.
If that's what you said originally, I'd say fine. But it isn't. You said it went to empty when you grounded the gage side. Which is expected. Since it's an open with the connection apart, it's going to float to full. Once you pull the connection apart, it doesn't matter what you do to the sender side, it's not going to affect the gage. If it does, there's a new problem you'll have to deal with because electrons are going where they shouldn't.
Are you referring to Post #8? Please show what I stated originally, I'm confused here. With the connection apart it does not 'float to full', rather staying at 1/2 tank reading. The 'key' was used to activate the 'empty' reading in grounding the gauge side.
Last edited by synoptic12; September 11th, 2022 at 02:54 PM.
Are you referring to Post #8? Please show what I stated originally, I'm confused here. With the connection apart it does not 'float to full', rather staying at 1/2 tank reading. The 'key' was used to activate the 'empty' reading in grounding the gauge side.
Yes, you are correct. It was my error as stated in Post #15 The bottom line: 1.) I tested the Sender wire (Pink) @ 1/2 gauge reading in grounding to the chassis, then turned the key "ON" and the gauge moved to "FULL". 2.) I then tested the Gauge wire @ 1/2 gauge reading in grounding to the chassis, then turned the key "ON" and the gauge moved to "Empty".
Initially, the fuel gauge was pegged (Full) for two to three days, then started going down slowly whereas it now reads about 1/2 tank. Whether this is accurate is unknown. The Youtube video inserted is the process I followed, yet adding an extra step in grounding the sender wire.
I'm having someone look at it this week. If it is related to moisture, where would the moisture be prevalent? By the picture I've inserted in Post # 8, does the rust appear to be a factor? Again, I would hate to replace the sender unit, then have issues with the tank down the road which would mean double the cost. 69HO43 said to try and keep the original tank: > "And if you pull the tank (drain it best you can first) do what you can to clean it out if it needs it. Try to reuse your old tank if possible as I'm not sure if the repro tank filler necks have been fixed to keep fuel from sloshing back out . If it's not real rusty/pitted inside or outside, you can probably reuse it. It'll just depend on condition as to how long the tanks last."
You can't tell just by looking at the outside if the tank is too crusty to re-use or not. You'd have to inspect inside as well. Just from the post #8, pic, I'd clean the surface rust off and perhaps re-coat the outside with some of Eastwood's tank renew zinc paint or something similar to give it a refresh. If the rest of the tank doesn't look any worse than the picture you showed on the outside, it appears it should be ok.
That ground wire could use a cleaning/reseating as well. Why it won't come off, I don't know, but it needs to. Clean all the corrosion off around the area and make sure the ground wire is attached well to a clean ground. Or if you're going to re-use it, clip it off and put a new eyelet on the end of the ground wire and screw it in somewhere else.
If you do drop the tank, I'd highly recommend replacing the sender at a minimum. Might as well, because you're going to take the old one out anyway, so it's kinda cheap insurance IMO. It's something you don't want to do more than once, regardless. The sender part number referenced before (25001613) is if you have a fuel pump return line and a vent line going to the carbon filter canister under the hood needing 3 lines. If you don't have a fuel return line on your fuel pump, then you'll need a 2-line sending unit on the tank, which is p/n 25001612 or equivalent. Spectra Premium brand is FG08A for the 3 line, and FG08B for the 2 line sending unit. They can both be had at RockAuto for around $50 either one.
The inside of the tank is where it really matters regardless of how clean it looks on the outside. The point is, you don't want the tank to turn into swiss cheese and start leaking fuel everywhere. It's really a judgement call. Sometimes you look inside a tank of 30+ year old car and it looks new. Other times, if there was a lot of water in the fuel, you can get lots of rust and debris. If you see lots of rust and pitting, it's something to be concerned about and then you need to make that call. It's easier to inspect once the tank is out, drained, and the sender is removed from the hole.
Even when empty, you don't want to cause sparks around the tank if fuel vapors are present. But look around inside the empty tank (a small telescoping mirror and an LED flashlight can do the trick) and make the determination.
I advise against using any kind of tank internal miracle sealer unless an aboslute last resort, as if it's not done properly, can flake off down the road and clog up the fuel tank. And if you do determine you need a new tank, I advise to buy a neck-less tank and have your current tank's neck removed and installed on the new tank. The aftermarket necks don't seem to vent properly when filling and you can't quite get the tank full without slosh back and kicking off the pump prematurely. Again, not sure if they ever fixed that issue on those aftermarket tanks with their necks (probably not).
You can't tell just by looking at the outside if the tank is too crusty to re-use or not. You'd have to inspect inside as well. Just from the post #8, pic, I'd clean the surface rust off and perhaps re-coat the outside with some of Eastwood's tank renew zinc paint or something similar to give it a refresh. If the rest of the tank doesn't look any worse than the picture you showed on the outside, it appears it should be ok.
That ground wire could use a cleaning/reseating as well. Why it won't come off, I don't know, but it needs to. Clean all the corrosion off around the area and make sure the ground wire is attached well to a clean ground. Or if you're going to re-use it, clip it off and put a new eyelet on the end of the ground wire and screw it in somewhere else.
If you do drop the tank, I'd highly recommend replacing the sender at a minimum. Might as well, because you're going to take the old one out anyway, so it's kinda cheap insurance IMO. It's something you don't want to do more than once, regardless. The sender part number referenced before (25001613) is if you have a fuel pump return line and a vent line going to the carbon filter canister under the hood needing 3 lines. If you don't have a fuel return line on your fuel pump, then you'll need a 2-line sending unit on the tank, which is p/n 25001612 or equivalent. Spectra Premium brand is FG08A for the 3 line, and FG08B for the 2 line sending unit. They can both be had at RockAuto for around $50 either one.
The inside of the tank is where it really matters regardless of how clean it looks on the outside. The point is, you don't want the tank to turn into swiss cheese and start leaking fuel everywhere. It's really a judgement call. Sometimes you look inside a tank of 30+ year old car and it looks new. Other times, if there was a lot of water in the fuel, you can get lots of rust and debris. If you see lots of rust and pitting, it's something to be concerned about and then you need to make that call. It's easier to inspect once the tank is out, drained, and the sender is removed from the hole.
Even when empty, you don't want to cause sparks around the tank if fuel vapors are present. But look around inside the empty tank (a small telescoping mirror and an LED flashlight can do the trick) and make the determination.
I advise against using any kind of tank internal miracle sealer unless an aboslute last resort, as if it's not done properly, can flake off down the road and clog up the fuel tank. And if you do determine you need a new tank, I advise to buy a neck-less tank and have your current tank's neck removed and installed on the new tank. The aftermarket necks don't seem to vent properly when filling and you can't quite get the tank full without slosh back and kicking off the pump prematurely. Again, not sure if they ever fixed that issue on those aftermarket tanks with their necks (probably not).
Thank you very much for the exemplary detailed information. I've checked one fuel tank (Spectra Premium) in asking if the flapper is inserted in the filler neck and it "is not". Checking Precision Fuel Tank with O'Reilly and have not heard back as yet. Thanks for that valuable information (flapper) which I did not take into account. One problem after another and in this generation it's getting worse. A great many hide or do not display the critical information which I dislike. Again, your input has been well received and most appreciated.
Here is an issue that 69HO43 brought to my attention should I need a tank. It's good that we have such knowledgeable people such as 69HO43 to provide technical information detailing the facts. I did not even think of the filler neck flapper. Good thing I have not purchased as yet. Still making calls regarding the aforementioned. Filler Neck- Flapper
Last edited by synoptic12; September 12th, 2022 at 10:13 AM.
You might be trying to fix something that isn’t broken.
the gauge on my 72 Cutlass acts the same way. The gauge on a 68 Chevelle i had back in the day worked the same. These GMs with the flat rear mounted tanks seem to stay at full longer than they should and then start dropping rapidly. I have heard others on here state the same thing.
I said nothing about a "flapper". All the tanks with filler necks should come with one if designed for unleaded fuel, so the unsuspecting can't fit a regular leaded or diesel pump nozzle into it.
I was talking about the aftermarket filler necks that do not vent properly while you're filling them, which has nothing to do with the flap. In fact, the vents are basically slits and holes above the flap.
Anyway, the aftermarket necks allow fuel to gurgle up too soon and prematurely cut off your fill nozzle when filling with gas at the gas station keeping you from getting a completely full tank. It's likely an engineering design flaw within the aftermarket fill necks. I've never owned an aftermarket tank, so I can't speak to it directly, but I've heard a hundred stories from those who have bought aftermarket G-body tanks. Not all do it I don't think, but I don't know which brands actually do. Something about the angle of the neck entry or something, I'm not sure what is believed to be the root of the issue. You can still fill the tank, it's just more of an inconvenience that has to be dealt with. People end up modifying the neck to accomodate, but to me, I'd rather just use the right one if possible.
If I put in a new tank, I'd have my OEM filler neck removed from the original tank and installed into the new tank. If you wanted to do it yourself, it's just soldered into place. Fill the old tank with water first to prevent fuel vapors from burning and having fire department sirens in the neighborhood, then just heat the area around where the filler neck enters the tank. As the OEM solder melts, just work the neck out of the tank, applying heat to the solder joint as necessary to keep it soft.
Then take the neck and the new tank to a reputable radiator repair shop and have them solder it in if you don't think you could do it yourself. It probably wouldn't cost much for a rad shop to do it, if you so choose.
Last edited by 69HO43; September 12th, 2022 at 11:38 AM.
You might be trying to fix something that isn’t broken.
the gauge on my 72 Cutlass acts the same way. The gauge on a 68 Chevelle i had back in the day worked the same. These GMs with the flat rear mounted tanks seem to stay at full longer than they should and then start dropping rapidly. I have heard others on here state the same thing.
I believe you may be correct. I was uncertain of that fact. Thanks much.
I said nothing about a "flapper". All the tanks with filler necks should come with one if designed for unleaded fuel, so the unsuspecting can't fit a regular leaded or diesel pump nozzle into it.
I was talking about the aftermarket filler necks that do not vent properly while you're filling them, which has nothing to do with the flap. In fact, the vents are basically slits and holes above the flap.
Anyway, the aftermarket necks allow fuel to gurgle up too soon and prematurely cut off your fill nozzle when filling with gas at the gas station keeping you from getting a completely full tank. It's likely an engineering design flaw within the aftermarket fill necks. I've never owned an aftermarket tank, so I can't speak to it directly, but I've heard a hundred stories from those who have bought aftermarket G-body tanks. Not all do it I don't think, but I don't know which brands actually do. Something about the angle of the neck entry or something, I'm not sure what is believed to be the root of the issue. You can still fill the tank, it's just more of an inconvenience that has to be dealt with. People end up modifying the neck to accomodate, but to me, I'd rather just use the right one if possible.
If I put in a new tank, I'd have my OEM filler neck removed from the original tank and installed into the new tank. If you wanted to do it yourself, it's just soldered into place. Fill the old tank with water first to prevent fuel vapors from burning and having fire department sirens in the neighborhood, then just heat the area around where the filler neck enters the tank. As the OEM solder melts, just work the neck out of the tank, applying heat to the solder joint as necessary to keep it soft.
Then take the neck and the new tank to a reputable radiator repair shop and have them solder it in if you don't think you could do it yourself. It probably wouldn't cost much for a rad shop to do it, if you so choose.
Thank you very much. I'm sorry in misconstruing the message of the 'vent' as opposed to the flapper. However, I certainly take your input with respect. The problem may have been solved as the fuel gauge is operating normally. When you made mention of the 'moisture' problem as possibly being a factor, that started me thinking. One of my brake hoses gave way a couple of weeks ago as I barely made it to a service station without crashing. I had to leave the car there for two weeks before he could make the repair. In the interim, the car was left outside in some inclement weather, namely some heavy rainstorms. My car is always garaged. Anyway, would that have been a factor for the 'moisture' problem? Sounds kind of odd that the car being left outside for 2 weeks would cause that issue. At this point, I'll probably let it go to empty, then fill up again. GM recommends using a fuel additive when the gas gauge is stuck. I've been using Gumout regularly to forego any problems with the fuel delivery system. A stuck float could have caused the problem but I'm uncertain of that. At least I will not have to fork out $800.00.
Last edited by synoptic12; September 12th, 2022 at 12:56 PM.
September 4th, 2022, 04:08 PM
Seeking Assistance / Fuel Gauge Inoperative
