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Opeler
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Discussion Starter · #1 ·
Finally got the fuel tank cleaned and relined today in my 70 GT using the Eastwood Co kit. Now, can anyone tell me how to test the sending unit? The fuel gauge isn't reading anything and I need to find out if it is the unit, gauge, or the wiring. I want to at least be able to get the tank reinstalled and the car running again before I have to put it in storage for the winter.
 

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Any meter that can test continuity or resistance can check the sending unit attach POSITIVE probe to corresponding outlet on S/U . Ground the ground lead move the float up and down the wires (there should be One wire that makes a U shape ) If I remember correctly it should read around 4 to 6 ohms at lowest point (empty tank ) to 0 or 1 at top full tank. ( I could have these figures backwards) if it doesn't read but the wire inside S/U is in good shape take it and bead blast it ( carefully though) tape up the float, unless it is brass (mine was not) be carefull not to stay in one place very long clean the wire and especially the contacts on the float . Then Clean the sleeve that covers it all, plenty of crap collects in here. Put her back together and check ohm's again this should work as long as wire isn't broken if it came loose at the end that can be soldered if it broke in the center of run you will have to find a piano wire or something of the same guage as to keep the same reading resistance. If it reads and your guage doesn't, check wiring back to guage the best way is to turn ign. on and ground the pos. lead this should peg your guage to full . If wiring is good and this does not work I believe your guage is probably bad.Good luck

RITTER
 

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0-90

GM fuel senders operate on a 0-90 ohm resistance value.

The easiest way to clean the resister wire well is carefully with a pencil eraser. It remover the tarnish, shines it right up, and who doesn't have a pencil? Be careful to go gently and along the direction of the wire to not break the resister wire.

Grounding the + wire to check for full scale movement is really easy and works well to roughly check the wiring and the meter. Also try a 1/2 watt or greater, 30 ohm resister from radio sack. It might set you back a buck, but with the 3 in the package you can simulate 30, 60, 90, 15, and 10 ohm values between the + and ground to check the calibration of the meter through the full scale.

Fuel tank senders that sit for a long time at a certain level tend to develop corrosion at the point where they sit, leading to all kinds of faults. The easiest way to prevent this is to fill the tank all the way up when you store you Opel, or any car, for a prolonged period of time. Remember, full tank and empty carb and the fuel system should be good to go for storage!
 

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Opeler
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Discussion Starter · #5 ·
Unfortunately, it gets a little to cold here in Iowa to be able to work on the car. I plan on building a new garage in the spring to have room for all 4 cars. Then the GT and our PT Cruiser can go in the new garage and our truck and van in the old. Our old garage is just to tight to be able to work on cars without having the door open. Building a large 30 x 26 garage with plenty of shop space. Can't wait!
 

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Since you guys are talking about gas tanks I'd like to share with you something we found last week on our GT. The bodyshop guy was sanding on the rear near the back taillights and all of the sudden got a big gas leak. He called me up and when I got there there was coffee cans all underneath the car catching gas.

It turns out the fuel line outlet just as it comes out of the gas tank was rusted bad, the vibrations from the sander finally broke it and was leaking like a sieve. Our Opel had a rubber boot over that line as it exits the gas tank that was trapping water and rust.

You might want to check that area on your cars to see if your line is doing the same thing.
 

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Opeler
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Discussion Starter · #8 ·
Not a problem. Went to a hydraulics shop yesterday and got all new brass fittings and a new galvanized fuel line. Just have to bend the line to the right shape and will be like new. Got lucky, the guy really knew his parts. Just looked at the old one and dug around in a lot of boxes from every corner of the shop and found the exact parts for only $10.
 

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Opeler
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Discussion Starter · #9 ·
Got the fuel tank back in the car today. After a few failed attempts with various tools, ended up using needle nose vice grips to tighten the fitting for the fuel line. Put gas in the tank and although the sending unit still doesn't work, I am getting gas to the carb. Now just have to get the timing set so I don't have flames shooting out the carb. :D At least it is turning over and getting fuel. Hopefully will get the timing set tomorrow. A former Opel Rallye owner is coming over tomorrow to show me how to adjust the timing since the wonderful Chiltons book just says "use a timing light and either advance the timing or retard the timing as necessary". Not to helpful for a newbie. Then maybe I can get back to them #*%@ brakes.
 
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