Fuel tank sending units, GM, pt# 25093562 have now gone the way of the GT tail lights .
I have called Auto Zone, NAPA, Pep Boys, Smiths Auto, and 4 different dealers, yet it's to no avail. They say that they are unable to get 'em, don’t stock it, or its not even coming up in their systems.

I NEED a new sending unit in my GT, as it's not even remotely close to where the actual level is in the tank. I'm not going to guess what amount of fuel is in the tank by calculating the mileage between fill ups, so I need to pick your brains as to go about solving this dilemma.

In the repair manual for the 88 Fiero, it states that the gauge is full @ 9o ohms and empty @ o ohms. Is there something out there that I can replace just the unit with, so that the gauge is going to be able to read the correct fuel level?
Has anybody else had this issue, and what were your solutions to the problem?

Yet another Fiero part gone forever Gentleman…scratch and save to buy what's left, as it's going, going….and now yet another is gone….

[This message has been edited by mcaanda (edited 01-14-2004).]

over the next couple of decades we're going to have to become very adept at making parts from other cars work in fieros.

Have you tried calibrating the sending unit?

Since you're going to have to drop the tank if you find a replacement sender, why not do it now and try the calibration procedure described here first. You may surprise yourself.

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-d.

1985 2M6 SE (his)
1984 2M4 (hers)

Ratings don't make the world go 'round, but they are nice to have. If you find what I have to say helpful, please click on that Rate this member link over to the left and give me a positive.

Didn't somebody adapt one from a Corvette to work?

Does anybody have the article above done with pictures to see exactly what is being done? I think it would be easier for the "mechanically challenged" to get a better idea of what is being done.

The stock fiero unit is just a vertical structure with a horizontal arm and a float attached. We modified mine when I changed all my gauges to ISSPRO. It's a very generic-looking simple thing. You might try bending the float arm and trial and error with the tank out until you get it where you want it. I also think a VDO sender might work for you.

Here's a link with a pic from egauges.com - I WOULD NOT BUY from this guy - he stung me already ! But this will give you the info you need.

http://www.egauges.com/vdo_sgrp.asp?Subgroup=Fuel_Senders&Cart=http://www.egauges.com/vdo_sgrp.asp?Subgroup=Fuel_Senders&Cart=

[This message has been edited by PaulJK (edited 01-05-2004).]

Hey i can come in handy! w00t! , When i first got my car the fuel sending unit just didnt work period.. In any case if you remove the entire sending unit from the tank, you will see a little half moon looking container with bendable clips to hold it closed. "im asuming this is almost identical to my 85 GT sending unit" and there should be a coil inside this housing that a small metal probe slides up and down on as the float arm moves. Mine was covered in varnish from years and years of gas and also sitting for 4 years in cheap gas. In any case you need to make sure your resistance coil in the sending unit is clean, also make sure the probe doesnt have anything on it. I reccomend a small screw driver to scrape any built up varnish from the sending unit resistance coil. Also be sure to clean the entire housing and the plate it sits on with the flexible clamps on it to be sure your getting a good ground. In fact clean any metal parts on and around the sending unit housing, Be careful with those clips as they are probably very fragile, my dad and i broke 2 off and had to drill holes in the assembly and bolt it together with some stainless steel bolts. If you have a volt meter you can test the continuity of the resistance coil by grounding the negative probe and running the positive up and down the coil.. If you want to actually test it in the fuel tank before you put it back in "im not sure if this is dangerous but.. i'm not dead, even so be careful" Take a long piece of plywood and lay it across your your open trunk and set the fuel tank on it , from here the wiring on the sending unit can reach the plug. then you can place it in the tank and lift an end to see if the guage moves inside the car. You can also just move the float arm up and down by hand but personally i would make sure it works in the fuel tank first before putting it back up under the car. If you have any questions E-mail me and i'll try and help .. I've had my fuel tank out 3 times now cuz of that thing! Have fun!

J. Carson

It's not necessarily the sending unit. I can just as easily be the gauge in the dash. Don't ask me how I know . You can check the resistance by disconnecting the connector in the engine compartment. Check it once with tank near empty and then fill up and check it again. If you are close to the 0 ohms and 90 ohms spec, go after the gauge in the dash panel.

The sender for the 2.5L is still available. What are the differences? can you take parts off one to fix the other?

I think the 2.5 uses a smaller pump I'm not sure but i remember reading it somewhere.

The part in the sender that is causing trouble is the same as almost every 1980's GM car. You can adapt it easily, just need to look around at the wrecking yard for one that is similar. The pot should read 90 ohms when the arm is all the way up and 0 ohms when it is all the way down.

I substituted mine with another GM car sender that I picked up from the junkyard,I can't remember which car it was but I think it was a Buick or olds and that is not Fiero specific other GM will fit just take your multimeter to the junk yard and measure the readings across the wiper coil.

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Tuners of the Quickest 4.9
12.51@118 mph

4.5 (RSR)Hi Perf. Caddi-V8
In place and running.

it is eazyer to index the gauge
then to mess with the sender

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Question wonder and be wierd
are you kind?

hi summitracing sells two gm 90 ohm sender units that could be adapted
part # sum-290180 and # sum-290181 they also have chrysler and ford senders that could problbly be adpated

Used a sending unit off of a 1984 S-10 V-6, simply removed the sender from the assembly by grinding off the tack welds, then tack welded it on to the Fiero assembly. Parts cost was about 40 bucks from the dealership and worked 2 out of 2 times

quote Originally posted by spark1: The sender for the 2.5L is still available. What are the differences? can you take parts off one to fix the other?

The sender for all 87 & 88s are the same. The fuel pumps are the same size outside dimensions so the 4 cylinder unit can be used.

I have some of those I think.

[This message has been edited by Indiana_resto_guy (edited 01-06-2004).]

Yes, they are still available, yet at this pricing, I'd be out of my mind to look into this here, and it's @ GM Parts Direct pricing...I dont even want to think what a dealer is going to ask for it!

Being that they are the same, Im going to call today and see what they are going to say about the 4 cyl's. When I called, I stated it was the 2.8, so I suppose that we can go from there.

Looks like there are a few things that I can try before totally giving in to not having a gauage to tell me what the level is.
Thanx!

--Mcaanda

[This message has been edited by mcaanda (edited 01-14-2004).]

Mine didn't work at all. If you disconnect the connector from the tank (it's on the firewall), you can check there to make sure it's not a problem with the gage.
This really wasn't difficult to repair, just detailed.I follwed the directions from the internet that said to solder jumpers in the board till you get to 0 oms and 90 ohms taking into acct the screws that hold the board on also adjust the 0-90 ohms range.You need to drop the tank anyway if you were to completely replace it, so you might as well attempt the repair. It could just save you money.It's not a complicated system at all.

Once you remove the sender from the tank, you can disassemble it, clean it, and put it back together. It was suggested to me that vinegar would remove the deposits that cause the resistance to change.

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Raydar
88 3.4 coupe.

Coming soon...
88 Formula, presently under the knife.

damn wish i tried vinegar... heh just be sure to test it before you put it back in... i HATE dropping the tank on my car haha

quote Originally posted by Raydar: Once you remove the sender from the tank, you can disassemble it, clean it, and put it back together. It was suggested to me that vinegar would remove the deposits that cause the resistance to change.

Carb cleaner and/or electrical parts cleaner works well for me.

Isn't the sending unit part of the 'whole thing' that is replaced with a "new fuel pump assembly" ??? No. Probably not.

Not sure, but it may be possible that the specific sub-component is 'discontinued' (actually replaced by another part).

Aftermarket replacement of sending unit may also be an option.

quote Originally posted by Indiana_resto_guy: The sender for all 87 & 88s are the same. The fuel pumps are the same size outside dimensions so the 4 cylinder unit can be used. I have some of those I think.

I used the GM part number 25091515 from GMPD in my 88 Formula...it worked perfectly. It's been in use for the past 8 months with no problems.

Steve

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1988 Formula 3.4L
1/4 mile ET: 15.514 86.27 MPH

Whelp, the sending potentiometer portion of the fuel tank sending unit seems to be toast.
( I forgot to list in the original post that I knew that there was going to be a possibility of this happening. The original sending unit that was in the tank was shot, and the pipes that were coming out of the tank were broken, cracked, and not safe at use at all…it just looked beat up )

I tried to clean it, and the resistance is still way too high. It seems that there was something that happened to this small item, which is now un-repairable. It almost looks as if there was a small arc that happened, and toasted the board as well as the resistance wire that is wrapped around it.

I will be checking on the S-1o possibility here shortly, and see what the local auto parts stores are going to have to say about what they have in stock.

I called Summit, and I can get a VDO style sender that will work w/ the stock gauge ( pt# VDO-2260080 for 29.95 + S&H. ) This is going to require the tank top to be cut, but hey, I got a bag full of dremel bits that are begging to be used anyhow. You do what you can when you wont spend the 2oo.oo+ on things that you really don’t need. I have a new pump for a 94 Grand Sport Vette, and only a bad level indicator.

I will keep you posted on what I find out from here.

[This message has been edited by mcaanda (edited 01-14-2004).]

glad you got it sorted out ... I had a strong feeling the VDO would work ...

[This message has been edited by PaulJK (edited 01-12-2004).]

If we could find a unit that's the same distance top to bottom inside the tank and has teh GM top them that would work. Just may require longer ruber hoses to connect it up and swapping the electrical connectors.

quote Originally posted by PaulJK: glad you got it sorted out ... I had a strong feeling the VDO would work...

Yes, I have called on all the parts that are listed above, and sent mail out to WCF ( Eric I think ) and have to yet get a reply. I called all the local parts stores, and it seems that they too are not carrying the S-1o's parts either. I asked about the other years, and the same thing is coming up. They don't offer just the sender portion of the unit, so I guess that I'm up that "preverbal creek" in regards to getting the OEM style equipment.

The VDO unit is not what I really wanted to do, as cutting into the tank is never really the "preferred" method of fixing things, but it seems that in this case, there is going to be little choice.
I could go out into the yards, look for one that is ok, but how are you really going to know unless you drop the tank and check it that way...It's too much hassle, and the equipment that your buying is still almost 2o years old. I'm going to call the dealer one last time to check on another lead that I got last night, and if this call doesn't pan out, Summit's 8oo number is the next that I dial.

Sounds like it's going to be a good thread to document the progress, as if this is the way that things are going to be forced to go, there are those that are going to be wanting to know about this fix as well….

--Mcaanda

[This message has been edited by mcaanda (edited 01-14-2004).]

Your experience is definitely paving the way on this one. I'm not sure how much you wanna pave, but there is an article on the lambo kitcar forum by a guy that made a gas tank to fit into the stock fiero location and it held 15 gallons. The stock tank has a wide seam and this guy just made his tank to expand and occupy the space wasted by the seam. If you're into building a tank, I'll find the thread for you .

http://www.gastanks.com

Maybe they can find you one. Or get you the parts you need.

Kind of bass-ackwards, but I used the Summit VDO unit in my bastardization of a project.. Explanation: The Fiero uses a 0 ohm empty, 90 ohm full signal, and the gauge I'm using needs 90 ohm empty, 0 ohms full. Basically I just put the float ball sticking out the other end of the unit.. But what I did was to remove the stock Fiero sending unit "can" from the whole pump/tube assmebly. Then I took the round top off the VDO unit (the part that you would have to cut into the top of the Fiero tank if doing it the hard way) and attached the VDO sender to where the Fiero sender used to be. I bent the VDO float arm to the same shape as the old Fiero arm, and poof, it works great. The VDO unit is like most newer cars these days, where it uses a ceramic circuit board and traces for the resistance instead of a coil of resistance wire. Should out last the car. Don't have any pictures of it, but it's not too difficult to do. Now, if your whole pump/tube assembly is junk, then you've got to fix or replace that too.. I was going to fix mine but luckily found a good condition one in a parts car. (tubes are OK, but they weren't sealed to the top round part.) Anyway... Just my experience. Let's keep these cars alive! Oh yeah, now where is that really cool capacitive fuel level sender?? It's used in airplane tanks, it's a stainless tube that just sticks into the tank, and it's capacitance changes as the fuel level rises and falls. Supposed to be really accurate. Probably too much $$ unless you're building a super-Fiero though.

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Bob Williams
Multi-colored '87 Mutt, a work in progress! (3800SC installation in super-slow-motion progress... I turn the key and it starts, I turn the key off and it stops. I give it gas and the axles spin. WOOHOO!! It works!! It works!! It works!! Did I mention IT WORKS!?!?)

Found a Solution!

Look here for info, pix, and pt #'s:

Fuel Tank Sending Unit Solution!