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Fuel Gauge FAQ

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Generously donated by member Kevin Kelleher

Be sure to take out the shipping wire before installation. Otherwise follow these instructions I collected before doing mine:A few years ago, as I was staring right at the fuel gauge, I suddenly saw it drop about 1/8 tank or so. It made me blink. The next fillup, I realized I hadn't been hallucinating when I noted the needle didn't go all the way to the full mark. And now it gets all the way down to the "R" before the "Get Fuel,

Dummy!" light comes on. It appears to me the sensor float must've sank just a little.

So it's bugged me for a couple of years, but not enough to do anything about it, until today. While waiting for things to cool between some experimental tune-up tests, I decided to get a look at the thing. I'd saved some posts from here on the topic, so I was ready to tackle it. I took out the floorboard in the trunk area, opened up the little rubber cover, and unplugged the sensor. Shorting the fuel gauge wire to ground gave me a FULL tank reading, which I hadn't seen in many years, so I realized everything else is good but my sending unit must not be working right.

Here's another peeve to add to my list of how Saabs are NOT designed for easy maintenance or repair. I could NOT unscrew that blasted plastic cover ring over the sensor. My fingers weren't strong enough reaching through that hole, and I didn't have the special Saab tool for doing it. Someone talked about making a strip of metal into a "U" shape, but after puttering around with ineffective makeshift tools I got fed up, plugged the connector back on, covered it, put the floor back in, and went back under the hood for the rest of the day.

Here's my question: If I =DO= manage to get that sender out, can I open it up and repair it? Is it worth it to do this? How much does a new one cost? And does anyone sell a tool or know of something I can use to get some torque on that plastic ring?


- = M = -


I used the gentle hammer and screwdriver technique to remove as well. Worked just fine. I tried to repair the sender once unsuccessfully. They do come apart easily but can be difficult to repair depending on the problem. The float rides up and down on a central bar and has two thin metal tabs that touch fine wire on either side. Mine had a broken wire and I could not find a perfect match to replace it. I tried something close and the guage never came off showing full even though the float was moving correctly. I gave up and got one out of a parts car only paid $20... definitely the way I would go if I had another problem.


89 SPG 96 9KCSE

Thanks, John.

I suppose that once I remove it, I might as well look inside and see if it's something I can repair, but now I'm wondering if it's worth the trouble.

I've had bad luck with used parts and tend to avoid them now if I can, unless it's something like a headlamp lens. Mechanicals I've tried used broke on me within weeks of installing them, and I ended up getting new replacement parts anyway. Any idea how much a new one would cost? Guess I'll check some of the SaabNet sponsors and see. If I can find one for under $50, I'll do it.

Appreciate your info! Thanks again.

Monster, I had to change mine since it wasn't working. Forget about the tool. I used a flat blade screwdriver and with a hammer gently tap the plastic cover ring.Don't use something too sharp you just want to nudge to break it loose.

Posted by Ryan Goldade

Try a pair of tongue and groove pliers (channel locks)...Adjust the handles to be just as wide as the outside diameter of the retaining ring. Use the rubber handles instead of the plier end to grip and turn the ring. I have done this a few times now on a few different cars. If you live in the Northern states or anywhere where they use ethanol or a similar alcohol based fuel additive in the winter months you will be better off using a new sending unit. In Sweden they do not add alcohol to their fuel, therefore the sending units are made of plastic that was not made to contact alcohol. This causes swelling and degradation in the float and in time inaccurate readings. Depending upon the year of your saab...sending units will cost from $35-$65.00 NEW. Used units will probably deliver similar results to what you have now.

Good Luck...!


Dan, I suspect you got a used sender that wasn't accurate. And Scotty, in all likelihood, it's the sender, but there's an easy way to test it.

All you need is a piece of wire. Here's what you do:

Open the trunk and remove the floorboards. In my '87 hatchback, I first open the rear section where the spare tire is, then unhook two rubber straps that act as a hinge. Then take that section out. The front board is held in by four metal clips, and if you slide it aft, toward you, about an inch, it will then lift out. (If you don't have a 3-door, I have no idea what you'll need to do.)

Now look over on the right half, and you'll see some wires disappearing down under a round rubber cover. That's where the fuel gauge sender unit is. Pull the rubber cover off, and you'll see a 3-wire connector on the top of the unit. Unplug that connector.

My understanding from Ryan G. is that different years have different configuration connectors, but the function is the same. One wire, usually the one that's alone, and usually black, is the ground wire. The other two wires (mine are brown and gray) go to the two sensors... one is the fuel level, and the other is for the low fuel light.

Take your piece of wire and insert it into the plug to short one of those two wires to the ground wire. Now go around and switch the ignition to ON, but you don't have to start the car. If your fuel light comes on, turn the switch off and go back out and short the other wire. :> If everything is working properly EXCEPT for the fuel sender unit, your fuel gauge should read Full... ALL the way Full! If it does, your sender is defective. If it doesn't, you have a problem elsewhere.

If the sender's bad, you're almost already there as far as replacing it. Make certain the replacement you get is for your year and model Saab, because they're not all common. All you have to do is unscrew that plastic ring holding it in, lift the old one out (have rags handy; there's gas in there!), insert a new one in its place, tighten the ring back, plug the connector back on, and you're back in business. Note the fuel level with the old sender unit before you start this project, then note it again after you replace it with a new one, and hopefully you car will tell you it has more gas after you've finished! :>

The problem I've run into is that ring is ridiculously difficult to loosen, and you can't get your hands around it. There's a special Saab tool for removing it, but experienced people on this BBS have told me to use either the handles on a pair of channel locks, or just get a flat bladed screwdriver and a hammer and tap the edges until it loosens. Some guys actually manufacture a U-shaped piece of metal and use it as a tool to grip either side. Good luck with whatever method you find. I watched a nature show on PBS where chimpanzees were using straw as a tool to get termites out of a mound, so I figure I should be able to make some kind of tool that will work. Or maybe I just need a good chimp to help me out?

I've been shopping and have found a sender for $61 at GAPA, and am still looking. I was hoping to find one cheaper. My feeling is that getting a used one from a junkyard is risky -- it's likely to be no better than the one you had (probably what happened to you, Dan!) so I'm opting for a new one. I haven't even bothered with my local Saab dealer, who would probably charge $200 for the stupid thing.

BTW, I use my trip odometer religiously as a backup fuel meter. If I've gone over 300 miles since the last fillup, I start looking for gas -- though I've done over 400 miles on steady highway trips before. The fuel low warning light is supposed to come on with 7 liters of fuel left, according to my manual, and when I see a steady light, I figure a gallon and a half, or around 40 miles to go. Those who trust lights and gauges will eventually flame out in the boondocks at night, though! :>

I'll let everyone know how it goes when I replace mine. Hopefully, it won't get to the point of using any of my wife's gardening implements this time. Please share info if any of you find a good source for sensors, and I'll do the same.

- = M = -

If the gauge reads low, it's either that the float in the tank has soaked up some fuel and is not floating as high as it should, or the electrical connections have higher than standard resistance. The latter problem is probably the most likely.

Begin by cleaning up the electrical connections, both at the plug on top of the sending unit, and where the ground wires connect to the frame of the car. Be sure to clean the ground connections both at the back of the car, and the connection where the battery ground wire connects to the frame. If that doesn't do it, then replace the sending unit if you want to.

Looking from the trunk. the sender is on the left side(larger diameter)

Where the two fuel lines are???


kevin O

It is not the large hole on the left. That is the fuel pump. It is the little hole on the right. Unscrew the retaining ring, and pull it out slowly. The fuel will evaporate pretty quickly and when it does turn the thing over a few times to see if the float inside moves easily from top to bottom. If the float sticks at all expect the problem to last until you replace the sending unit. New sending units cost from $35-$70.00 and are considered a "wear" component in saabs (do not replace with a used one unless that used one is in better shape than the one you have...NOT LIKELY!). The float is made from plastic and that plastic swells when it contacts alcohol..(ie ethanol...fuel system cleaner...fuel injector cleaner...fuel tank cleaner...etc) In the northern states expect to replace the unit every 5 years or so, and in the south it depends on what goes into the tank...


ps- The best product to rid your hands of the smell of fuel is fresh lemon juice.

Changing my fuel gauge sender unit

Posted by Monster

Well, I just did it, and while the experience is still fresh in my mind, I thought I'd post the details.

As many of you know, I shopped around for awhile before ordering my new sender unit. I ended up getting it from Sobstory for under $50, plus a little more for shipping. That was a heck of a lot better than local parts places that wanted $110 plus two weeks to get it, or the rip-off dealership in town that wanted $209 for the part and would cheerfully replace it for me for "around $250, plus tax." Sheesh. Many have recommended getting junkyard senders, but I don't have access to many junked Saabs here in Northern Florida, and I've had lousy experiences with used mechanical and electrical parts. So I ordered a new one.

Mine's been reading about 1/8 tank low for several years, and never gets to up the full mark when I fill the tank. Otherwise, it works normally, including the low fuel warning light. My suspicion was that my sensor float wasn't floating as high as it should, probably as a result of soaking up some ethanol-tainted fuel on a road trip somewhere. I remember distinctly when it happened; I was staring at the gauge when the needle suddenly moved downward a notch and made me blink in disbelief. It never came up to full again after that.

Replacing it took me half an hour, and I went at a leisurely pace. I first clicked on the ignition without starting the car and noted the fuel level on the gauge. Then I shut it off and went around to the trunk. The rear floorboard of my hatchback is held on with two rubber straps. Unhook those, and the floor comes out. Then the front floorboard slides back an inch or two and lifts out.

Here's a tip for you! After you take out the front floorboard, put the rear one back in! Then you'll have a nice place to sit and work in there instead of trying to do everything leaning over the rear bumper.

Under a round rubber cover on the right side of the trunk is the sender unit. I disconnected the two prong connector to the fuel pump and then the small 3-prong connector to the sender unit, then moved that rubber cover out of the way.

Note that to test your fuel gauge and see if you have a bad sender, all you need to do is short the 3 wires in that fuel sender connector together, and click the ignition to on without starting the car. Your fuel guage should read all the way full and the low fuel light should come on with those wires shorted together. If that happens, the rest of your fuel gauge circuitry is fine and the sender is the faulty component. If it you get different results, you've got other electrical problems.

Anyway, to remove the sender you just unscrew the black plastic ring holding it in. That's not so easy to do without the special Saab tool made for that purpose. I wrestled with some channel locks and other tool handles, per the recommendation of people on this board, then gave up on that approach and decided to loosen it with a hammer and screwdriver. Putting the screwdriver blade on one of the ridges on top of the retaining ring and tapping it a few times got it loose. {{Thanks for the tip on that one, guys! :> }}

Once the ring is off I could just lift out the unit. Be careful doing this and don't pull it all the way out at once! Lift it up part way and let the fuel drain out of it into the tank. Have a rag handy and once it stops dripping, take it out the rest of the way.

Installing the new one is simply a matter of dropping it in. Mine came with a new gasket. I tightened the retaining ring as tight as I could by hand, clipped the connector back on, re-connected the fuel pump connector, then put the rubber stopper back in place. Put the floorboards back in, and I was done!

When I turned the ignition key to on, I discovered I now had another 1/8 tank of gas in there. Big dopey grin from me! I should have done this fix years ago. I went in and hugged my wife, the triumphant garage warrior with his latest conquest, and was rewarded with, "Eww! You smell like gas!" Women! Oh, well.

Sweeney, you asked about the float travel. Both my new unit and the old one would "thunk" when I inverted them and the float freely slid from end to end. It didn't seem there was much friction preventing the movement.

Andrew, I know you repaired your sender. I opened my old one (a small nut on the bottom of it holds the thing together) and inside I could find nothing wrong with it. The wires are all intact, the contacts are clean, everything moves freely. The problem is undoubtedly a soggy float. I doubt it would be economical to repair. I'm sure that if something else had been wrong with it, like the bad contact in yours, I would have been able to fix it as you did. But the cure for a slightly sinking float is beyond my patience.

Still, if anyone would like to have my old sender unit (which works, other than reading 1/8 tank low) I would be happy to send it to you for the shipping costs. Send me an e-mail if you want it.

Hope this helps anyone contemplating doing this job.

Added note the sender is shipped with a thin wire bent into one of the holes near the bottom of the sending unit. This thin wire should be removed prior to installation.

Warm regards,

- = M O N S T E R = -

(and Beastie) ==> '87 900T 158K

Re: Changing my fuel gauge sender unit

Posted by Ryan Goldade

In Reply to: Changing my fuel gauge sender unit

Great to hear that you finally got that fixed Monster. I also replaced another sending unit last night. I have replaced the unit in my '81 3 times this year. The one that I pulled out last night has a faulty float in it and I just replaced it in the middle of July. The float is full of gas. Luckily all saab parts are covered by a 1 year factory warranty so the cost isn't a problem. I was talking with the dealer about these things failing last night, and he told me that he sells them constantly. I went to the independent parts guy where I bought it and he told me the same thing. He wasn't surprised at all that it only lasted 2 months. He says that saab knows they made a poor product, but the part is discontinued and the car is too old to put any new engineering into. I guess $65.00 a year isn't that bad for maintenance.


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