When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
When I got the car, gauge didn't move at all or read fuel level, so we took tank down, called NAPA and ordered a new sending unit. Part arrives n checks out its the same and the float works and everything. Needle goes to full on ignition, All good. THEN first time I fill the tank I was all excited to see it working... and needle stops at 1/3 tank. Needle did move so im just curious as to whats wrong and how I could potentially fix. I usually drive it close to E (to not get stranded) but when filling it back up only takes 17-18 gals when its a 25gal tank... My first thought was a calibration thing but a quick google yielded nothing pertaining to that. Any solutions?
Nah I don't believe its the ground. I cleaned both surfaces well with sandpaper to ensure good connection
I'm not talking about the ground side of the circuit. I'm talking about the insulated side of the circuit having a defect in the insulation that is partially-grounding the gauge ahead of the sending unit.
You need to make sure the gauge needle can move freely from one end of the dial to the other. Disconnect the sending unit from the wire going to the front of the car and ground the side coming from the front. Turn the key on. The gauge should go to E. Remove the wire from ground, and it should go to F, or possibly beyond it. If it does these things, the gauge is fine, and, yes, you might have a sending unit calibration problem.
What year/model is this car, anyway? I can't tell just from the gas gauge alone.
Its a 83' delta, and I recall when I changed it a time ago, my dad had me see if it went both ways to E & F so im assuming gauge is good. Referring to calibration thing, I think the only available unit was a "Spectra Premium" . Now was there anything I was supposed to do to calibrate new unit, or is it just defective?
Spectra Premium is the only brand of replacement sending unit out there as far as I know. There's not a huge market for sending units for not-highly-collectible 40 and 50 year old cars, so I'm glad that anyone makes them at all. I have a Spectra Premium unit in both my '67 Delta and '78 Toronado.
As far as I can see, they can't be calibrated. It could be that your unit is defective, or it could be that you have to get used to a new normal. If the gauge needle goes no lower than 1/4 with the new sending unit when the tank is actually empty, I would suspect a problem with the new sending unit and have them replace it. If the second one does the same thing, then it's likely that that's as good as you're going to get, and you'll just have to remember that 1/4 means empty. The important thing here is that you actually have a functioning gas gauge that tells you when it's time to add gas. What gauge marking it specifically points to when this happens is really a secondary concern.
These old gas gauges were never terribly accurate even when they were new back in the day, and I always found them to be very non-linear. The needle would move slowly between F and 1/2 and then move like a bat out of hell from 1/2 to E, so "1/2" never meant that I actually had a half-tank of gas, and I had to remember this. I had a '90 Ford Taurus whose gas gauge was one of the worst in this regard.
If the gauge needle goes no lower than 1/4 with the new sending unit when the tank is actually empty
This is definitely the lesser of two evils, but my gauge doesn't read higher than 1/4 tank, so when gas is low I have no indicator of when i'm close to the end. Knowing when a tank is full is way less useful when I fill the tank every time. All in all, I've lived with it for past year, can and will continue to do so if there's no other option.
OK, I misunderstood your problem. I thought the gauge wouldn't go lower than 1/4. You're saying that it just goes between E and 1/4? That's definitely unacceptable and suggests a problem with the sending unit. When you take it off the tank, you might put an Ohmmeter across the leads and see if it reads 90 Ohms when the float is all the way up and close to 0 Ohms when it's all the way down. If it does, then I would make sure the float moves freely. Presumably one or the other of these will be the problem.
The new sending unit for my '78 Toro is a correct replacement, and it works just fine as far as where the gauge points when the tank is full, 1/2 full, and near empty. The new sending unit on my '67 Delta is not factory correct as those are not made, so the one I used is for a '72 Olds or Buick full-size. It's a drop-in replacement as far as fit and connections, but it is not baffled, so the needle does bounce around a bit. More importantly, it does not travel properly between F and E. Rather, when the tank is full, the gauge reads about another hash mark's worth beyond the F, and when near empty, isn't much lower than about 3/8. But it works, and, a functioning gauge is better than none at all.
I am having the same problem on my 67 Cutlass. I now have two new sending units and both indicate 1/4 when the tank is full. The gauge checks good. Anyone have a solution for this?
I've heard of aftermarket sending units that have floats that float in water...but not in gasoline.
The wire harness could be grounded somewhere. Disconnect the wire from the sending unit, the gauge should go over-full. Ground that wire, it should go to "E".
Could, I suppose, be a problem with the power supply TO the gauge.
You need to see a schematic of how the gauge circuit is supposed to work.
Order a replacement sender, before reinstalling the tank add a jumper wire from the tank to a good ground, and another jumper from the dense wire to the gauge. With the tank empty, make sure the gauge actually reads empty. Then add 25 gallons, hopefully it reads full. If so, drain the tank, reinstall, and test again. Good luck
Let me clarify. My original 52 year old sender was unreliable at best. I ordered a new sending unit and installed it. With a full tank, it reads 1/4 on the gauge. When I disconnect the ground from the sending unit, the gauge drives to empty. When I disconnect the power to the sending unit, the gauge drives to full. I ordered another sending unit. Before installing in the tank, I connected the power and ground and moved the arm up and down with the ignition key turned on. The new sender still only reads 1/4 on the gauge with the arm at full up. What am I doing wrong?
When I disconnect the ground from the sending unit, the gauge drives to empty. When I disconnect the power to the sending unit, the gauge drives to full.
This doesn't sound right. You test the dash gauge as follows. Find the point in the gauge-to-sending unit wire where the wire from the dash connects to the non-ground wire from the sending unit. This connector is usually behind the license plate or perhaps in the trunk around where the trunk latch is. With the ignition ON and this connector disconnected, the gauge should go to F or probably well past it. Then ground the wire coming from the gauge with the ignition ON. The gauge should go to E. The second half of your statement ("when I disconnect the power to the sending unit, the gauge goes to full") sounds correct, although you technically can't disconnect power to the sending unit because the power is supplied through the dash gauge, then through the sending unit, and then to ground. There is no direct power connection to the sending unit. When you separate the connector I talked about above, you are removing power from the sending unit, but what you're really after here is to create an open circuit. The gauge, which is just a 0 (empty) to 90 (full) ohm ohmmeter, reads an open circuit as infinite resistance, which is a lot more than 90, and that's why the gauge usually goes well past the F mark.
But the first half of your statement does not sound right. When you disconnect the ground but leave everything else connected, you have created an open circuit, and the gauge should read F, not E.
Last edited by jaunty75; August 3rd, 2019 at 09:21 AM.
The sending unit is not powered its the ground side of the gauge. The gauge has constant power when the key is on and the sending unit provides various degrees of ground. If the gauge is working but the level of adjustment is off it may be due to the chassis ground at the gauge.
Ok. Broke out the ohm meter. (Reading the chassis service manual helps.) New sending unit has max of 33 Ohms at full vice the 90 required - kind of correlates to tank reading just over 1/4 when full. Purchased at Rockauto. Anyone have a recommendation for another source? I thought I read that only one company makes them.
Ok. Broke out the ohm meter. (Reading the chassis service manual helps.) New sending unit has max of 33 Ohms at full vice the 90 required - kind of correlates to tank reading just over 1/4 when full. Purchased at Rockauto. Anyone have a recommendation for another source? I thought I read that only one company makes them.
A few questions.
1. You said in post #10 above that you bought TWO new sending units. Do both show the 33 ohm reading?
2. What brand did you buy? Rockauto shows four different brands of sending unit for a '67 Cutlass. Spectra Premium, Dorman, Liland Global, and Autotecnica. For all we know, they're all the same things with just a different brand name on it.
3. The first one shown on the Rockauto site, Spectra Premiums FG88A, is apparently available through any auto parts store (I haven't checked the others). Here's the O'Reilly listing. It lists the specifications, which show that the rheostat range is 0 to 95 ohms, which is as it should be. If your unit is showing only 33 ohms, and it's a Spectra Premium unit, it could be defective. A reading of 33 ohms max would certainly correspond to a gauge reading of around 1/4 to 1/3.
The various Rockauto offerings show different pipe diameters. Assuming one of those is what you need, I would very much try to buy it through a local parts store where you might be able to bring your ohmmeter to the store and test it right there before bringing it home.
Last edited by jaunty75; August 4th, 2019 at 09:28 AM.
Feeling like a doofus here. I did not realize there were so many options. My car is a Cutlass Supreme and when I looked under that model, there were only two options, and only one of those is available - which turns out to be a 35 Ohm unit. When looking under the Cutlass model, the options you displayed appear. Guess I have some learning to do about Rockauto. Thank you for your help on this. Now I can order the correct unit.
It isn't just rockauto. You really have to be careful when doing online parts searches (or even in the store!). When I was doing the search, I just picked Cutlass. Rockauto shows F-85, Cutlass, and Cutlass Supreme as choices. As different as these models might be in some ways, I would have found it hard to believe that the three models used different sending units. When you search under F-85, you get the came choices as you do for Cutlass.
June 25th, 2019, 09:12 AM
fuel sending unit issue ?
