bowtieboy56
Contributor
Posts: 111
Loc: new zealand
Reg: 05-01-11
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08-17-12 09:34 PM - Post#2260484
after noon everyone, i have spent my saturday working on my 57 6 cylinder and took her out for a spin, 
its nearly spring here and i am super keen to get this project on the road legal and get some miles on it.
my trouble today was when the car sits with the key on the fuel gauge reads ok, but as soon as i drive off the gauge moves up to full and moves around, now i know that the needle moving is a normal chevy thing but i am at a loss as to whats causing the change as i drive off, so i stoped and got out,shock the car and up it would go to full again!  then settle back to just under half full when the car isnt moving!.all wiring was then checked,all terminals are firm and clean.so i am guessing its got to be the sender?any one had this happen too them?
regards chris
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retiredrich
Contributor
Posts: 809
Loc: NE
Reg: 10-05-07
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08-18-12 05:35 AM - Post#2260543
In response to bowtieboy56
Hey Chris, A few years ago, the needle on my gauge read full until it got down a ways on fuel and then it jumped around a lot. I replaced the sender and all has been good since. 
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 acardon
"9th Year" Silver Supporting Member
Posts: 9471
Loc: DFW TEXAS
Reg: 03-25-05
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08-18-12 06:33 AM - Post#2260559
In response to bowtieboy56
That sounds like a bad ground on the tank. The sender is grounded to the tank and the tank is supposed to be grounded to the body. Put a ground wire from the sender to a clean metal spot on the body. To keep from disturbing the sender attaching screws, I clamped a bare wire to the senders fuel tube with a small hose clamp and attached the other end to a screw, with a star washer, through an existing hole in one of the tank mounting brackets.
Don
66 Corvair (driving)
57 2dr HT (restoring)
56 2dr HT (waiting to be restored)
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bowtieboy56
Contributor
Posts: 111
Loc: new zealand
Reg: 05-01-11
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08-18-12 07:06 PM - Post#2260757
In response to acardon
thank you Don, i will do just that, and if the problem persists i will pull the sender unit.
cheers chris
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55MAS
Senior Member
Posts: 1145
Loc: North Coast, Ohio
Reg: 12-19-01
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08-20-12 02:32 AM - Post#2261180
In response to acardon
That sounds like a bad ground on the tank. The sender is grounded to the tank and the tank is supposed to be grounded to the body. Put a ground wire from the sender to a clean metal spot on the body. To keep from disturbing the sender attaching screws, I clamped a bare wire to the senders fuel tube with a small hose clamp and attached the other end to a screw, with a star washer, through an existing hole in one of the tank mounting brackets.
Since this topic is discussing fuel gage operation, this is as good as any place to ask a possible related question. The original wire from the sender to the gage was a smaller wire, 20 ga? What effect, if any, if a PO replaced the original wiring with a larger wire, say 14 ga, as a replacement due to an overall resisance change. Would the gage read as original, or would there be a possible offset in the reading? Thanks.
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acardon
"9th Year" Silver Supporting Member
Posts: 9471
Loc: DFW TEXAS
Reg: 03-25-05
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08-20-12 05:48 AM - Post#2261209
In response to 55MAS
A larger wire will not affect the resistance reading. Since there is such a small amount of current flowing in the wire from the gauge to the sender, the voltage drop is very little if any.
Most of the aftermarket harnesses have larger than stock wires in all the circuits. The factory wiring is just too small, especially in the headlight and ignition circuits. 20 gauge wire in a 13 amp headlight circuit is just way too small. 
Don
66 Corvair (driving)
57 2dr HT (restoring)
56 2dr HT (waiting to be restored)
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Edited by acardon on 08-20-12 05:51 AM. Reason for edit: No reason given.
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55MAS
Senior Member
Posts: 1145
Loc: North Coast, Ohio
Reg: 12-19-01
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08-20-12 09:06 AM - Post#2261287
In response to acardon
Thanks.
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bowtieboy56
Contributor
Posts: 111
Loc: new zealand
Reg: 05-01-11
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08-21-12 01:40 AM - Post#2261595
In response to acardon
wow! thats a very good point Don! i am looking at up grading the stock head lights on my 57 and never considered the load on the wire.
what would be best to do? replace the wire or introduce a realy ?
regards chris
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acardon
"9th Year" Silver Supporting Member
Posts: 9471
Loc: DFW TEXAS
Reg: 03-25-05
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08-21-12 06:28 AM - Post#2261629
In response to bowtieboy56
With stock headlights, either would be OK. If you want to use some hi-output headlights, relays will take the load off the headlight switch and allow more current than the circuit braker in the switch has (13 amps).
Don
66 Corvair (driving)
57 2dr HT (restoring)
56 2dr HT (waiting to be restored)
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bowtieboy56
Contributor
Posts: 111
Loc: new zealand
Reg: 05-01-11
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08-22-12 01:10 AM - Post#2261942
In response to acardon
great advise Don thank you very much
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bowtieboy56
Contributor
Posts: 111
Loc: new zealand
Reg: 05-01-11
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08-27-12 12:34 AM - Post#2263518
In response to bowtieboy56
ever had one of thoses days where you wish you hadnt got out of bed!!!! 
after following Dons advise i added a earth wire to my sender unit.....
it made my fuel gauge go straight to full so i decided to remove the sender unit,.....easier said than done, my 57 had been fully under sealed so i started with scraping off the black gunge,first screw i tried to undo snapped @!!!
thats where i pulled the plug !!
now i have to drain/and remove the whole tank to tap out at least one thread
but i have a question! the factory screws holding the sender in, what are they???? they are not allen key, not posi, not square ??help!
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acardon
"9th Year" Silver Supporting Member
Posts: 9471
Loc: DFW TEXAS
Reg: 03-25-05
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08-27-12 06:48 AM - Post#2263574
In response to bowtieboy56
The screws are "clutch head". Link to clutch head screwdrivers. I have removed them by grinding a flat blade screwdrive down so it just fits diagonally in the screw, but if they are rusted, that may not work.
Don
66 Corvair (driving)
57 2dr HT (restoring)
56 2dr HT (waiting to be restored)
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Edited by acardon on 08-27-12 06:50 AM. Reason for edit: No reason given.
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 WagonMan
"3rd Year" Silver Supporting Member
Posts: 1296
Age: 65
Loc: SW Kansas
Reg: 10-26-04
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08-27-12 07:30 PM - Post#2263828
In response to acardon
The screws are "clutch head". Link to clutch head screwdrivers. I have removed them by grinding a flat blade screwdrive down so it just fits diagonally in the screw, but if they are rusted, that may not work.
Those are one of the best tool investments there is for anyone working on an old Chevy.
Charles
57 210 4dr. Wagon(bought '82)
-350/700r4 Mild Custom
56 BA 4dr. ht.(bought '98)
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29 Ford Sedan(bought '75)
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bowtieboy56
Contributor
Posts: 111
Loc: new zealand
Reg: 05-01-11
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08-28-12 01:43 AM - Post#2263892
In response to WagonMan
thank you guys, i did think they looked like the screws in the back of the horn ring.i had even done what i usually do with any old rusty bolt/screw and as it moves i turn it both in and out to help it un seize....but no luck with these ones!!
and i used a flat blade screw driver to snap off the first one, i ordered a new sender unit yesterday and its here today so thats my fathers day present for this sunday! i will drop the whole tank out ,remove all the screws and fit the new one...
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bowtieboy56
Contributor
Posts: 111
Loc: new zealand
Reg: 05-01-11
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09-07-12 10:04 PM - Post#2267558
In response to bowtieboy56
after breaking one of the screws in the sender unit.
today i tried to remove the rest, no luck at all. so i removed the tank, and i am glad i did!! 
the reason the screws would not move was the amount of rust in the tank,i removed heap of rust scale from the tank!
the tank is totally rotten, so is the lower filler tube and the joining hose, and the vent hose.
and so is the fuel line to the motor!
so out came to shopping list, for lots of new bits!..and come up with a plan on how to find the money to buy it all! haha.on the up side i have the new fuel sender and as Don sugested i have soldered a earth tab on to it and made a wire to the body,...i never expected to find so much rust,i am amazed my engine even runs!!
| shoebox's spin my wheels |
Edited by bowtieboy56 on 09-07-12 10:07 PM. Reason for edit: No reason given.
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