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Thread: Anybody had fuel gauge problems with VDO & Fiero setups?

  1. #1
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    Anybody had fuel gauge problems with VDO & Fiero setups?

    When I built my Diablo Roadster I changed out the fuel pump for the carb v8 Im using. I noticed that the fuel sender was in really bad shape. The contacts at the top of the tank where rusted. I went ahead and used it anyway knowing I would swap in another fuel sender assembly in the future. Getting tired of not having a working fuel gauge I purchased a used fuel pump/sender assembly from another fiero that I was told it came from a working Fiero. I installed it today and the needle goes way past the Full mark. The VDO gauge is the correct GM 0-90ohm part, I even took out the gauge and hooked it up to the 0-90ohm sender in my drag car and it worked perfect. Theres only three wires on the fiero pump- ground/sender/pump. I know that the wiring is correct, triple checked, its right.... I put a ohm meter to the sender wires after I installed it and it goes to full ohms, so the sender isnt working. I know I should have checked it before I installed it, but it appeared to be in really good shape.

    I guess Im going to order a brand new fuel sender assembly but thought I would check here first to see if there is something Im missing...
    Thanks!
    ~Tony

  2. #2
    Senior Member Joe 1320's Avatar
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    Re: Anybody had fuel gauge problems with VDO & Fiero setups?

    I saw this and had hopes....... turns out mine is the opposite. An actual full tank of fuel reads 1/2 on my gauge, as the fuel tank drops to about 5 gallons, the gauge reads near empty and it sits there until the I get about 3 gallons when the needle starts swinging wildly. ??? I'll be watching this as well.

  3. #3

    Re: Anybody had fuel gauge problems with VDO & Fiero setups?

    OK, lets see if we can break this down. The pump sender works by creating resistance that is measured. This where the 0-90 Ohm is done. Where 0 is empty and 90 Ohm for full. For a Fiero you should have a pink and black wire at the fuel pump. Shorting the together would create a 0 Ohm reading and the gauge should read empty. Then build an 90 Ohm circuit (22+68 Ohm resistors in series) and bridge to the pink wire and it should read full.

    My first guess is that the fuel sender is bad. It is very rare for the gauge to go out. Especially if it is new. I would check all of your wiring from the pump to the gauge one more time, then pull the sender and run a bench test. Do not worry about being flustered here. Solving problems is what building cars is all about. (or I feel it has become)

  4. #4
    Moderator FunnyWheels's Avatar
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    Re: Anybody had fuel gauge problems with VDO & Fiero setups?

    Call VDO and they will give you the correct info for your car. Have your Fiero VIN ready.

    Dave
    If you're not confused, you're not paying attention.

  5. #5
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    Re: Anybody had fuel gauge problems with VDO & Fiero setups?

    Already called VDO (now they are called something else) and they verified that I had the correct gauge. I took the gauge out of the dash and crawled under the car with it and wired it directly to the harness going directly to the sender/pump assembly and it still pegged out way past full. There is something wrong with the sender, I just gotta drop the tank again and see whats going on.

    I also hooked up another after market temp gauge straight across the intake manifold from the VDO temp sender and it runs almost 25 degrees hotter than the VDO gauge. Not sure what was going on, I borrowed my friends thermal temp gun. Its the kind where you just point it toward the heat source and get a reading. It measured excatly what the aftermarket gauge is reading. All this time I though my car was running around 150 degrees when warmed up, but its actually around 175-180 degrees at full temp. So I called VDO and got the correct temp sender part number and ordered a new one from summit today. Its weired cause I used the sender that I got with the gauge set from VDO and its giving off bad temps.

    The other thing Im still not happy with is the wheel alignment. I took it in to 3 different places and one place didnt even want to do it cause the frame has been stretched, all the others had racks you have to drive upon and they said the front end was to low to drive it up. Finally found a place that had some boards to help get it up on the rack. Found out that the front passenger side inner bushing was bad, still charged me $129.00 to do 1 wheel on the rear the other was good. I wasnt to happy about that but they said that when I got the front fixed they would do it for free since i already paid for the whole alignment. Got a repair bushing from Rodneys (what a great place to business with) I put it in and went back to the same place that I went before and now they dont want to do the alignment unless I pay another $129.00... What a mess, Im not about to pay them again- so I got to find another place to get the alignment... Mean while I driving this car that feels like it wants to go in 4 differnt directions at 80 miles per hour. I guess Im done venting, its fore warning to you who are still building your projects- even when its looks like your done- they seem never to be completely done!!
    Keep on building!!!

  6. #6

    Re: Anybody had fuel gauge problems with VDO & Fiero setups?

    Finding a good alignment place for a Fiero is hard to do. Best of luck to you.

  7. #7
    Moderator FunnyWheels's Avatar
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    Re: Anybody had fuel gauge problems with VDO & Fiero setups?

    I will look for the alignment specs for a Fiero. I have them written down in a note book somewhere, any place can due the alignment with those specs. Mine cost me $121. What do you have for suspension?

    Dave
    If you're not confused, you're not paying attention.

  8. #8
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    Re: Anybody had fuel gauge problems with VDO & Fiero setups?

    Quote Originally Posted by FunnyWheels
    I will look for the alignment specs for a Fiero. I have them written down in a note book somewhere, any place can due the alignment with those specs. Mine cost me $121. What do you have for suspension?

    Dave
    I got my car alignment done today at a Firestone Service Center about 10 miles from my house. Its a brand new store that has a pit style alignment machine. Made it real nice not having to drive it up on a rack, they only charged me $80.00 for all four corners and did a real good job. All the workers started out just asking if they could just take a few pics of the car- "sure go for it" I told them, then they started asking to borrow the car for the weekend.. "sorry no can do"... But on the way home I noticed some popping sound and a little pull on the front drivers side wheel when I got on the brakes. Got it home and jacked it up and saw that there was movement on the drivers side inner tierod when the tire was wiggled. Great! I paid to have the alignment done once then found out I needed to replace the passenger side steering rack bushing and inner tie rod, did that- now got alignment done again, now I gotta fix the drivers side inner tie rod and get it aligned AGAIN.... I think Im just going to purchase just a whole rebuilt/reconditioned Fiero rack and get it aligned one final time........ This what happens when you try to turn a old crappy Fiero into Lamborghini diablo roadster...

  9. #9

    Re: Anybody had fuel gauge problems with VDO & Fiero setups?

    They should have noticed that when doin the work

  10. #10
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    Re: Anybody had fuel gauge problems with VDO & Fiero setups?

    Quote Originally Posted by luapynot

    I guess Im going to order a brand new fuel sender assembly but thought I would check here first to see if there is something Im missing...
    Thanks!
    ~Tony
    Just my 2 worth but I'd just replace the sender assembly and move on to something else. Fieros rarely had accurate fuel readings even when new, but you can easily fix that if you're careful. Good news is that you can now get a new assembly from the Fiero Store (discontinued from GM.) Bad new is that it's $200.

    http://fierostore.com/Product/Detail...0912&d=246&p=2

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