Fuel sending unit replacement for an accurate reading

[Meanmyz]

Hi guys. I have a fuel gauge that has read inaccurately since I purchased the car in 2012 ('95 Z).

My question is, can you buy a new fuel sending unit without buying the fuel pumps?

So far my research as found that the GM part number is 19180770. OEM units appear to retail for about $370. I have to guess that this price includes pumps???

It will be a winter project for me to fix this. The problem I am having is that after filling the tank full, it doesn't take but a few miles to immediately lose the first bar on the gauge. After that, my fuel gauge goes down faster than the actual fuel level of the tank. By the time my gauge reads empty, I will find that I still have about 5 or 6 gallons in the tank.

Sure, I can continue to drive knowing that I have fuel, but then my "check gauges" light is on because according to my fuel gauge, I should have been walking already!

When I had Marc do my engine package for the car in 2014, I had him take a look at the sending unit. He looked it over for problems, with nothing apparent, but the problem persists.

This car has been a fun project for me with the goal of making it "awesome" when I get done. I do plan on keeping it. I add these statements in helping you assess my plan of action for repair. Thanks!

[BigJohn]

Yep that’s how it was set up at the factory

My gas gauge is the same as yours

It is to keep you from starving the fuel pumps

[Meanmyz]

Yep that’s how it was set up at the factory

My gas gauge is the same as yours

It is to keep you from starving the fuel pumps

Yes, but I shouldn't have that much gas in the tank when it says I am empty. I have two low mileage Z's and two more C4's to point out that this is the one with the problem!

Edit - John, 5-6 gallons is a guess, because I couldn't remember. I think it is usually more. I agree there should be fuel in the tank to not starve a pump and to keep it cool.

[Meanmyz]

I apologize if this appears to be a dumb question.

Can you buy an LT5 fuel sending unit separate from the pumps?

[Demps]

Bend the arm of the float.

Ted

[Flyman 27]

You can buy the sending unit without the pumps, search around the net. I can't remembered where I ordered from.
I was told that the few gallons in the bottom of the tank prevents the fuel pumps from overheating.
When my gage says empty &n shifts in to reserve mode, I still have 4 gallons left. I was told that this was correct.

[Jagdpanzer]

I’ve been looking for the same thing for years and so far have not found one as a separate replacement part. There are outfits that specialize in rebuilding old fuel tank level senders. The couple I’ve inquired with rewind the resistance strip by hand and charge $100+. Our senders are the same standard GM 90 ohm swing-arm potentiometer used on many other GM car models from 1960s to 1990s. Strange it’s not available as replacement part.


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[Meanmyz]

Thank you guys for your answers.

Phil, your answer tells me that no, you will not find a GM part without pumps and really gives the answer I am looking for.

Flyman, I am guessing these are aftermarket, and while they may be quality, I will look and do some more research.

Bending the float is easy, but also hit and miss. What would have bent it out of place in the first place? I would save the money and do that on my daily driver, not this car, and I am guessing you would feel the same way.

Thanks guys.

[conesare2seconds]

Funny enough, I’ve always had the opposite issue with my C4s - flat out of gas with bars still showing on the gauge. And the first 1/2-tank goes down slowly while the indicator races toward empty below half a tank indicated. I think there is a plastic bladder in the tank that can collapse over time and interfere with the sending unit. You have a good problem, I think.

[Demps]

So...I know a guy that...

When you put the sender [back] in the float can hang up. First, while getting it all in through the tank opening. Second, once in the tank IF one were to reach in to position the assembly it is possible to push against the float arm.

All of this is assuming the range of measurement is there. There are some posts here or CF (check Cliff's solutions) on how to measure resistance. I'm also a K.I.S.S. follower, & would slightly bend it (float) up if the sender has been removed lately.

Ted

[Meanmyz]

So...I know a guy that...

When you put the sender [back] in the float can hang up. First, while getting it all in through the tank opening. Second, once in the tank IF one were to reach in to position the assembly it is possible to push against the float arm.

All of this is assuming the range of measurement is there. There are some posts here or CF (check Cliff's solutions) on how to measure resistance. I'm also a K.I.S.S. follower, & would slightly bend it (float) up if the sender has been removed lately.

Ted

Yep, I can see how that could happen from your explanation. And agree on your fix (KISS). That is probably how it got goofed up in the first place...that a service tech bent it. I know from the Carfax that it was at the dealer for a no start after it sat for a couple of years.

I haven't myself ever worked on a fuel sender, so I am learning.

[Flyman 27]

I was told by a very reliable source (-=Jef=-) that the sender unit is the same as a standard C4. So you could find a deal on a standard C4 complete unit & swap the sending unit. That would be the least expensive way to get a new sending unit.

[jss06c6]

I've not heard of a "bladder" in the fuel tank, but here is a tray that lies directly below the sending unit arm and float. There is a chance that your float arm somehow got bent to the side slightly during installation. This would cause the float to hang up on the lip of the float tray. I would expect, however, that this would cause you to show fuel still in the tank, when in reality, the tank is nearly empty.[ATTACH]

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[Paul Workman]

Bend the arm of the float.

Ted

I wuz going to say that too!

Meanmyz, just to add: bend the arm toward the bottom of the tank, moving the float down equiv to about 3 gallons worth.

[Meanmyz]

I was told by a very reliable source (-=Jef=-) that the sender unit is the same as a standard C4. So you could find a deal on a standard C4 complete unit & swap the sending unit. That would be the least expensive way to get a new sending unit.

Thanks for the replies. And this is good to know. I believe this because it is the same tank as other C4's. It is just the piggy backing hardware and extra pump, which I already have.

[Meanmyz]

I wuz going to say that too!

Meanmyz, just to add: bend the arm toward the bottom of the tank, moving the float down equiv to about 3 gallons worth.

Thanks Paul. I think I will look to see what I have in the tank and current condition before ordering and maybe just do this.

Depending on condition, I wonder if there would be benefits of a new sock and pumps on a 60k+ mile car that has had another 100 HP added to it with Marc's 510/350 package.

[Marc Haibeck]

I have been cleaning the fuel level sensor as a repair procedure for quite a while. Recently I have encountered two units that would not stop skipping resistance at less than 20 ohms. That's about 3 to 0 bars on the gauge. This can cause the nasty jump from 3 to 0 bars in just a few miles.

I'm using a Stewart Warner universal fit sensor and fabricating an attachment to ZR-1 sender assembly. It's a modern thick film design. I get them from Summit Racing. Number SWW-439363-D. $37.

[carter200]

This is also a good time to think about changing out the plastic “y” for the billet replacement unit I machine. It will not break nor leak like the discontinued plastic one will. If interested contact me via email. Thanks for looking.

[conesare2seconds]

Marc, thanks for your post and finding a solution. Also, Jssc06c6 is almost certainly describing the cause of my old car’s behavior. The myth of the tank bladder: busted.

[Jagdpanzer]

Thank you Marc for sharing this information. I was also thinking about going the same route. Looks like a reasonable cost solution that solves another parts availability problem. Time to dig out that spare ZR-1 gas tank pump/sending unit assembly I’ve been holding on to for years with a defective level sensor.


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[TX '90 ZR1]

This is also a good time to think about changing out the plastic “y” for the billet replacement unit I machine. It will not break nor leak like the discontinued plastic one will. If interested contact me via email. Thanks for looking.

I'll second this!
I had a fuel pressure leakage issue that I finally traced to a small crack in the fuel sender/pump unit "Y".
Might as well eliminate a possible future issue while you are there.
;)

[Meanmyz]

I have been cleaning the fuel level sensor as a repair procedure for quite a while. Recently I have encountered two units that would not stop skipping resistance at less than 20 ohms. That's about 3 to 0 bars on the gauge. This can cause the nasty jump from 3 to 0 bars in just a few miles.

I'm using a Stewart Warner universal fit sensor and fabricating an attachment to ZR-1 sender assembly. It's a modern thick film design. I get them from Summit Racing. Number SWW-439363-D. $37.

Hi Marc,

Thanks for the information! With all of the info supplied here, I will troubleshoot and if it is the sender itself, I will keep this in mind as it would be the cheapest way to fix this issue. You have supplied a direct answer/solution to my question. Thank you!

[spork2367]

You can buy the sending unit without the pumps, search around the net. I can't remembered where I ordered from.
I was told that the few gallons in the bottom of the tank prevents the fuel pumps from overheating.
When my gage says empty &n shifts in to reserve mode, I still have 4 gallons left. I was told that this was correct.

Not available without pumps, and hard to find period. The whole units are available about two places for 340-370 dollars.

I was told by a very reliable source (-=Jef=-) that the sender unit is the same as a standard C4. So you could find a deal on a standard C4 complete unit & swap the sending unit. That would be the least expensive way to get a new sending unit.

Priced a standard C4 assembly lately? Out of stock a lot of places and 150-200 for the assembly without the pump.

[Flyman 27]

I've seen them for less than this:

https://www.ebay.com/i/351242969272?chn=ps

But Mark's idea of using a customized universal sending unit is great, should fit the bill for most of us if you don't mind a little work.

[Flyman 27]

I have been cleaning the fuel level sensor as a repair procedure for quite a while. Recently I have encountered two units that would not stop skipping resistance at less than 20 ohms. That's about 3 to 0 bars on the gauge. This can cause the nasty jump from 3 to 0 bars in just a few miles.

I'm using a Stewart Warner universal fit sensor and fabricating an attachment to ZR-1 sender assembly. It's a modern thick film design. I get them from Summit Racing. Number SWW-439363-D. $37.

Mark,
Could you give us a little more info on what has to be customized in order to use the Stewart Warner sensor? Maybe a photo or 2?
It sounds like you have worked out the problem quite well.

[kr1276]

I ran into the same problem and have ordered the Stewart Warner unit to replace mine. Any pics or guidance would be appreciated. Thanks!

[Jagdpanzer]

Here is the one I converted to the SW sensor
9168916991709171


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[kr1276]

Jagpanzer,

Sorry but open your pics for some reason. Would you please send them to my email
kr1276@aol.com

Thanks,
Keith

[-=Jeff=-]

Phil,

did you bend the float rod on the new unit? I assume that is to match the movement and position of the OEM one correct?

[Jagdpanzer]

Yes, had to bend and shorten it some.

[-=Jeff=-]

Phil, Thanks, I have not had a unit out in a log while to know what it looked like.

[Meanmyz]

Thank you again Marc for letting us know of the alternative part and Phil, thank you for posting pics of your install.

This is probably what I will do.

[-=Jeff=-]

Hi Phil,

Which end of the float did you shorten? I should probably service my pumps (I have not touched them at all) and might fix the float at the same time as I think that is not accurate anymore

[Jagdpanzer]

The end of rod that inserts into the sender. Had to cut off the existing 90 degree bend.


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[Meanmyz]

Hi all,

I started this thread a little over two years ago. I just wanted to finish it up and say that last month, I took out my fuel sending unit with the intention of getting it fixed (it wouldn't read the fuel level correctly).

After calling to inquire and ask some questions, I sent my fuel sending unit to Tri Star Radiator, LLC in Seneca Falls, NY (http://tristarrradiator.com/). The business is run by Dan & Samantha Hora (very nice people to work with). The Hora's are very busy and did have about 4 weeks of work before they could get to my sending unit. When Dan, got to my unit, he called me to tell me what was wrong (from memory, I think that the ohms on my unit were reading about 14 off).

Anyway, I got my sending unit back last week and installed it back in the car this weekend. It now works like new!

Because I wanted to post a follow up to this thread, I asked if they could send me a summary of what they all did (there was more than one issue). Here is there summary:

"Hello Jeff. Samantha here. Here is the basic rundown of what we did to rebuild your sending unit. First we disassembled and cleaned it up. We have a mixed media blaster that is very gentle with delicate parts but effective at cleaning rust and debris. Then we rebuilt your rheostat (fuel level sensor). We then went over all connections, and rewound, sealed and soldered them. After this, we modified your upper wiring harness so that it will not be prone to future issues like many of these units are. Lastly, we left your unit unpainted at your request. We usually ask the customers preference because we have rebuilt MANY sending units that are then submitted for judging on regional and national levels, so we know how important some of those labels and part numbers are. The epoxy paint that we use to coat the tops of the units to retard deterioration due to the elements, does obscure those fine details that can be important in a competition. Hope this helps and if you have any other questions, feel free to get in touch. Have a terrific weekend!"

Anyway, I also had them install a "Y pipe" type elbow that Carter here on the forum machines. I haven't posted pictures on a forum since the "Photobucket" debacle, or I would post a pic (I haven't taken the time to learn the new way.

The point of my post and thread IS: If you want your stock sending unit refurbished to "like new" operating condition, try Dan & Samantha Hora at Tri Starr Radiator (sendingunitguy@gmail.com)!

Meanmyz

[-=Jeff=-]

Good info.. what type of cost we they for that work?

[Meanmyz]

It was $219 with another $22 for Fed Ex back to me for a total of $241.

[-=Jeff=-]

seems reasonable considering what they are doing to it