News:

Due to a technical issue, some recently uploaded pictures have been lost. We are investigating why this happened but the issue has been resolved so that future uploads should be safe.  You can also Modify your post (MORE...) and re-upload the pictures in your post.

Main Menu

How To Match A Sending Unit to Stock Guage on '37 LaSalle

Started by carlhungness, August 30, 2020, 05:51:09 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

carlhungness

    It has been suggested I 'match ohms to the guage' on my fuel sending unit to the guage. Since the stock sending units for the '37 LaSalle are not obtainable, I'm seeking suggestions on what kind of sending unit I might use for my new (not yet found or built) tank. I have no experience with an ohm meter, so here's another learning experience.

bcroe

If you could supply the ohms vs deg curve for the gauge/sender, it
might be practical to assemble a modern device such as Scott Kent
did.  Bruce Roe

carlhungness

I sure appreciate the reply but have to say it surmises I have prior knowledge of another man's modification, and hope you can direct me toward same. I am imagining he took a modern device and (modified?) used it.

carlhungness

I just did a search for Scott Kent in the member's list and cannot locate him. Of course I'm trying to find out what he did regarding a sending unit.


bcroe

Cancel my reply, I was thinking temp gauge sender.  Bruce Roe

tripwire

Driving now:
2013 CTS4 Performance Coupe
1940 LaSalle 5229 C4D

A few I used to drive:
1976 Cadillac Ambulance
1969 Cadillac Hearse, Superior Body
1966 Buick Wildcat Hearse
1957 Ford Thunderbird x 3, 1 E code, 2 D code
1956 Oldsmobile Rocket 88 Sedan
1949 Mercury Convertible
1949 Mercury Coupe, Mild Custom
1936 Buick Special Sedan

harvey b

If you are making a custom tank,these sending units should work,you will have to run a seperate pipe for a fuel line?.the original was a gear type float and fuel line all in one unit.My 38 has its own fuel outlet on the tank.Harveyb
Harvey Bowness

Joe G 12138

       Carl: Being you are having a tank custom built, and also are running a 500 CI engine, I do have a couple of suggestions. You are starting fresh, and not 100% original, so use that to your advantage. First, The original sender unit has a 3/8" gas line pickup as part of the sending unit. It's an oddball; impossible to find new but expensive to repair if you are stuck with it and have no choice.  Set it up for a normal AC style as the shown on the Ebay ad. These are used on many GM cars. Then use a separate 5/16 fuel pickup like the rest of the world uses, either directly off of the tank or better yet a separate sending unit pattern boss on the new tank. Regardless, I would add a 1/4" fuel return line provision even if you are not sure you will need it, as it's tough to do later. A 500 ci behind that skinny grill could be a vapor lock candidate.
       I suggest these things because I'm in the process of modifying my fuel delivery system because I've had it with vapor lock / fuel boil and really want to use this car as intended; driving. So many have been down this same road before me for decades, but I'm hopefully going in a little different direction this time (but often there's "nothing new under the sun". I guess the point is that in addition to other fuel system routing changes, I've added a 1/4" fuel return system. I can't brag yet because I haven't blasted down the interstate yet on a long trip, but things are looking promising as I idled that thing for an hour and a half in 90+ Heat on the normal fuel pump. I also ran the electric backup for while without overpowering the carb and dumping gasoline all over. The return line is working great so far with the flathead but wasn't easy to do with the stock tank.     Joe Gibeault

TJ Hopland

I have a similar issue I am trying to deal with. 

If you have a mismatched set going can you add a resistor to at least get the empty to read correctly?   I started doing some tests yesterday.   Mine is the 0 ohms pegs the gauge full flavor.   Tank is currently empty and gauge was reading below E.   I found putting 1,000 ohms between the sensor and ground brings the needle just a hair above empty.   I think 50 ohms got it pretty close to full and 100 ohm steps were maybe about 1/6 of a swing on the gauge.

Will this mean that with that resistor installed my empty should be more accurate than it was before?  I have not yet filled the tank to see where it reads full and obviously have not run it down again after that to see how it reacts.   I seem to recall that that full was maybe 2/3 and it sat on empty for a long time but the recall is part of the issue.  Its seasonal and I don't often use a full tank so I can never remember how the gauge acts or how long its been since it quit bouncing on the corners.   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

carlhungness

My gas tank problems are now partially solved. My pal Karl Kinser, the world's most successful sprint car mechanic/owner and first class restorer just gave me a tank he says is out of a Packard Hearse. It has been modified with a  2 1/2" filler pipe coming out of the left top side, original one is plugged and it has a 1/4"pipe thread fitting on the top as well with a pipe that has been plugged, and drilled, presumably for a breather.
  The tank fits the LaSalle, almost. At the rear the flange just touches the two rubber grommets that hold the exhaust pipe hangar on and it appears as though I can remove about 1/16" of material from the flange to make it fit. Then all I have to do is make straps and figure out how to get the fuel to the engine and get a correct guage reading.
  I am pondering the suggestion of making a return line, and not sure how to plumb it, but it's a worthwhile suggestion I'll take into consideration. I also need to figure out what size line to run to the carb. The following statement was made and not sure I understand it.."set up for a normal AC style as shown on the eBay ad."
  I don't see an eBay ad and to me AC means air cond. So I'm flummoxed. Here's he quote.
  "Set it up for a normal AC style as the shown on the Ebay ad. These are used on many GM cars. Then use a separate 5/16 fuel pickup like the rest of the world uses, either directly off of the tank or better yet a separate sending unit pattern boss on the new tank."
  My Packard tank of course has a hole for a sending unit and will figure out what to do with it once I ascertain what kind of sending unit to install.

J. Gomez

Carl,

If you do a Google search on “fuel gauge ohms chart” you will find several sites showing the typical fuel sender ohms range.

The older GM senders were in the 0-30 ohms range these change in the mid-’60 to 0-90 and later to a higher ohms.

If you have the OEM gauge you will need the sender to match it in your case a 0-30 ohms sender. If you go with an aftermarket you will need the vendor specs for their gauge/sender.

If your fuel tank changed you may need to adapt a sender that would fit the tank and make several adjustment to the float arm to get the correct reading, which would be a big challenge.   ???

It recall a thread at the H.A.M.B. forum which someone was able to use a Chevy sender (same style as the one from Wes post on eBay) on the original ’37 tank, try searching the H.A.M.B. site.

I can tell you that a same GM sender that fits a Cadillac will go for $$ versus the same Chevy one for just $.   :o

Good luck..!
J. Gomez
CLC #23082

Mike Baillargeon #15848

Yep J has got it....

With regards to the sending unit....the tank people at Tanks Inc have a technical section on sending units....see this link...it helped me...

https://www.tanksinc.com/index.cfm/page/ptype=results/category_id=159/mode=cat/cat159.htm

Mike
Mike
Baillargeon
#15848

Joe G 12138

Carl: By eBay ad I meant the link that "tripwire" posted to the "OEM" style for most GM cars of this vintage. By "AC" I meant AC as in "AC Delco", or "AC Sparkplug", the in-house GM supplier. It's a very common 5 screw mounting unit with one wire connection, as opposed to the 6 screw 2 wire type used on many Fords and independants.  As Mr Gomez said, getting the right ohm range is key to beginning your shopping. That info isn't in the shop manual; maybe the tank vendors have it.   Joe Gibeault   

carlhungness

One of the links provided mykmlinkslifestyle resulted in a phone call from on Mike Leveille and I believe he can easily solve the problem. He can provide me with a voltage reducer for my gas guage at $45.00 and a sending unit for $145.
   My 'new' tank comes from I believe a Packard hearse so all I have to do is measure the distance from the opening of the sending guage unit to the bottom of the tank and he can make the sender to suit, leaving about 1/8" clearance on the bottom of the tank.
   It appears as though the rubber bushes that hold the exhaust pipe bracket in place may rub on my new tank, so I may have to do a minor mod to install the new unit, a lot less work than I anticipated. Plus, the tank was given to me, so I'm having a pretty good day!
   Mike has been in the business for over 40 years and has solved this problem previously, so thanks to all for the assistance.
   His website is http://www.mykmlifestyle.com/KM_Lifestyle_Fuel_Senders.html


Tom Beaver

Carl, do you have a copy of the 37 shop manual?  The manual shows an electrical diagram for the gas gauge and lists the resistance range for the tank sending unit.  Low float level (empty) 0.0 - 0.5 ohms, High float level (full) 29.6 - 31.3 ohms.  Any sending unit, doesn't matter where it comes from,  that will provide those resistances over the range from empty to full will work.  I had a capacitave sender that would work with 6V and the resistance range was adjustable.  This would work, had no moving parts.  Don't know where it is anymore, in some box someplace.  You might try and find one, save a lot of trouble.

Tom Beaver