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Hello everybody. I just wanted to once again say that I am SO grateful for this forum as every once in a while I look for others but cannot find any like it with as many helpful people. I'm not sure what I would do without you guys/gals!
So anyway, I received my "new" tank from Joe Lazenby last week [it's real nice] and I cleaned & painted the fuel sender unit I received from Mats Skön. I also received a barely used rubber seal for the sender.
My question is, what is the "proper" way to reattach the sender to the tank? I'm thinking that there might be some secrets because a) the unit needs to make complete contact with the tank for grounding purposes, b) maybe I need to use something else besides the rubber gasket to seal the sender with the tank like silicone, c) should I use stainless steel screws, d) will the typical lock washers be enough to make good contact (I painted the sender), etc.
See attached [terrible, low-light] image. As you might be able to see, this is a temporary installation using non-stainless screws/washers. Also, I stripped the paint from around the opening prior to installing - thinking I'd get a better contact. I have tested and see that I do have good continuity between the sender and tank.
Any tips, hints, suggestions, all welcome.
Thank you in advance.
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Tony 1958 P444 (44408), ID 187797 : See site for info
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By the way y'all, I performed the "bench test" this past weekend with 6V and both the gauge and sender and the result was 100% success. The gauge movement was very smooth from empty to full.
Only thing I need to do now is figure out how to a) get a new faceplate for the fuel gauge or b) refinish the faceplate! It looks gawd awful.
Thanks again for all the help!
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Tony 1958 P444 (44408), ID 187797 : See site for info
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Is this the 'slanted' gauge? as used in the 544's and 120's? As I understand it, the voltage difference is not a problem, since the system compares resistance.
I have two good spares if that's the one you need.
Steve
barongrey(at)mchsi.com
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No, unfortunately it is not the slated gauge... The 444 gauge is square. But thank you anyway!
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Tony 1958 P444 (44408), ID 187797 : See site for info
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Naturally! I could have just gone and looked at your dash, but that would be too easy!
There are places that specialize in redoing gauge faces. You might have to buy a Hemmings Motor News to find one.
As long as you're having one done, send in any gagues with discolored faces. One new one and some other older-looking ones would drive me nuts!
Steve
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As nearly everyone has stated below, there has to be a current running through the sending unit to ground. The fuel gauge works by comparing the resistance through the sending unit to the zero resistance to direct ground (at the gauge.)
That being said, here's some information you may find useful:
According to the Volvo shop manual, the sending unit should 'bottom out' - that is, stop falling - with the float approximately 1/2" above the tank bottom. This will give you a small reserve when the gauge reads EMPTY.
Also, the resistance across the sending unit should range from 12 Ohms (empty) to 200 Ohms (full.) You can measure this with the sending unit removed from the tank and the wire unhooked from it. As you mover the float lever and cause the little contact to move across the windings, you should have a regular progression of increasing resistance. If your meter keeps jumping from 1 to point-something, you have corroded wires and the little lever isn't making contact. This will cause your gas gauge to suddenly change readings, and may leave you with a situation where the gauge doesn't work reliably.
You can clean the windings with a solvent that leaves no residue. I use brake cleaner spray. Spritz the windings and immediately move the float back and forth several times. This should clean the corrosion off, but if the problem persists, you can CAREFULLY take the sending unit apart by gently prying the tabs up and pulling it apart.
There's nothing inside to lose, but you need to be careful that you don't damage or move the windings. You can use a fine grit sandpaper (like 800 grit) or even a pencil eraser to gently polish the windings. When you're satisfied that you've done as much as you can, reassemble the unit and test it again.
This isn't a big or complicated job, but having a working gas gauge when you have only a nine gallon tank will keep you from hauling a spare can of gas everywhere you go!
Good luck!
Steve
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Thank you very much - especially for the Ohm tests. I will need to test this soon. Which "shop manual" was this information in and what pages?
But I am very curious, how in the world would someone test this:
"... the sending unit should 'bottom out' - that is, stop falling - with the float approximately 1/2" above the tank bottom. This will give you a small reserve when the gauge reads EMPTY. "
Any ideas?
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Tony 1958 P444 (44408), ID 187797 : See site for info
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Remove the sender and put a ruler (NOT A PLASTIC ONE!) into the tank to measure the distance between the sending unit seat and the bottom of the tank.
While you're at it if you have gas in the tank, figure out about how full it is: 1/2. 3/4, etc. This will help you verify that you have your sending unit calibrated correctly. If you don't have any gas in it, only put in 4-1/2 gallons (1/2 tank) the first time you fill it. The gauge should read 1/2 full...
Using a square, place the flat plate of the sending unit on one side, and measure the drop of the arm. Using a square will ensure that you're getting a proper measurement at 90 degrees from the plate.
Source: Volvo Service Manual #9(91,94) - (green book) "Instruments and Heater System" for the P120. The P120 gauges are identical to the PV series.
I have a miscellaneous collection of these Volvo Service Manuals, and I try to add more when I find them. Also, you probably noticed that I don't restrict myself to a single model, although I only have a PV544 at this particular time.
The additional books help when I want to consider swapping parts from a different model Volvo. My Dad has a whole shelf of these books, but I'm going to leave them with him until I inherit his '65 P1800s.
Steve
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If the gauge is out of the car you can use a battery, test leads, a ruler, the vise on a work bench, a small board and a C clamp. Test leads to sender, battery and gauge, board to vise, sender to board with C clamp, ruler to tank, measure depth from flange to bottom, subtract 1/2", measure flange of sender to bottom float, add a little, move the sender, watch the gauge, bend sender float arm as required.
If the gauge is at the body shop with the car I question that it will work with ohm values. Mine were a bit different than those Steve cites, even though I think both he and I were using 12 volts. I think you are using 6 volts. It was fun to figure it out on the bench with my Stewart Warnere sender, Ron's article and some resisters. A side benefit is that you will better understand the "ground" problem.
Of course you won't be sure of your answer until you move this from the bench to the car (which I have not), but I think the measurement can be done as described above.
Keith
444 Project, Moline, IL
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Okay, so thus far we have:
1. Just use the gasket, no extra sealant
2. Screws make the ground so make sure they have good contact with the sender - by using a good lock or star washer should work
I agree that there must be some type of current (although it is probably very small) flowing to ground or else a resistance, which the sender provides, could not register on the meter.
Thanks all for the tips and please let me know if my outcome above is incorrect or if I need to do anything further.
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Tony 1958 P444 (44408), ID 187797 : See site for info
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Tony,
The only thing I would add to what has been said is don't use silicone between the sender unit and the rim of the hole in the tank, just the rubber gasket. Silicone will swell with the gasoline fumes and on contact with liquid gas. Pieces will slough off, drop into the tank and then plug up your fuel line. Don't ask me how I know. ;-(
Bob S.
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Not to be disagreeable, but there HAS to be a small current running through
the sender or there is no way for the resistance change to have any effect
on what the dashboard gauge shows.
I have had some problems getting a good ground on gas tank senders on 122s
so what I did was to run an auxiliary ground wire from one of the sender
mounting screws to one of the tank mounting screws. Since there is rubber
between the sender and the tank and caulking between the tank and the body
there is room for a bad connection, especially if you use lots of caulking.
The auxiliary ground wire solved the problem completely.
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George Downs Bartlesville, Heart of the USA!
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You're correct George, there must be a ground for continuity, but I'm sure there is no electrical current passing through the sender. If my PV wasn't strored away for the winter, I'd want to confirm this. So, considering the rubber sealing gasket at the tank, the only means to obtain ground is through the screws. It appears that Tony's sender has been painted black and maybe that's why all I've seen are bare metal where the screws attach. Adding a ground wire ensures the circuit is grounded and complete. Personally, I'd just not want any random sparks in the vacinity of a tank of gas!
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Cam a.k.a. CVOLVO.COM
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What activates any kind of electric meter is current flowing through it.
It is a very small current, admittedly, but if there is no current there is
no activation of the meter and it has no way of telling what to show.
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George Downs Bartlesville, Heart of the USA!
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Cam;
George is right of course...current has to flow...that's the point of an electrical circuit!...in the case of a tank sender, it is very small, sure...but interrupted by an open ground, and the effect is the same as when you interrupt the current to a light bulb.
George's solution to bridge the sender gasket and tank mounting putty is also the most effective way of assuring the ground to the sensor...although starwashers, scrapped painted surfaces and anti-corrosive zinc paste would work just as well, and look original.
Cheers
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I have never done anything but unscrew and rescrew the senders. The ground should be effected by the screws, contact between the sender flange and the tank is not needed.
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Good point. I think I realized that [contact between the sender flange and tank is not needed] a bit after I cleaned off the paint around the rim of the tank sender opening and saw how thick the rubber gasket was... Doh! Nothing a little more paint can't handle. Thanks!
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Tony 1958 P444 (44408), ID 187797 : See site for info
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Hi Tony:
I'm positive that there is no electrical power running through the tank sender. It actually behaves as a variable resistor, to the temperature gauge. I took one apart and what you see is a brass arm, that attaches to the float rod. There is about a 1" section with of wound wires, that the arm passes over. I'll see if I kept the fuel sender to explain better with a picture of the internals.
It's nice to see your latest pictures and hope you have a chance to get inside the body shop. When I did my Amazon-S, I actually spent the better part of 6 weeks inside the body shop, doing all of the "apprentice" (grunt) jobs.
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Cam a.k.a. CVOLVO.COM
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Cam,
I only wish I had the time to be at the shop. Luckily I work Sunday through Thursday so I have Fridays to check out the progress and snap some pictures. I'm sure it will be a few weeks before anything is accomplished. From what Henry tells me, he is going to get the car blasted first, then primed so he has a clean surface to work from for taking care of the bad metal.
Thanks again.
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Tony 1958 P444 (44408), ID 187797 : See site for info
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