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Positively charged petrol tank
https://auszookers.com/forum/viewtopic.php?f=5&t=31494		 Page 1 of 1
Author:  Mj28792 [ Tue Mar 27, 2012 3:51 pm ]
Post subject:  Positively charged petrol tank
So I have recently purchased a 89 sierra that has a 16b conversion and a few of your other basic mods eg body lift, 2inch suspension lift and 31" tyres .
I was working on it the other day .. Fixing some of the previous owners workmanship and I noticed my petrol tank has a positive charge to it ?? This has kind of concerned me as I didn't kno if it was normal for a petrol tank with an external electric fuel pump .. It only happens when the ignition is on , I know this because I did some investigating with the test light. But still couldn't find the cause ??

Should I be conserned ?? :?
Author:  just_cruizin [ Tue Mar 27, 2012 3:56 pm ]
Post subject:  Re: Positively charged petrol tank
Yes, may spark. And with a positive charge it will be acting as an anode in a galvanic reaction and will corrode
Author:  Mj28792 [ Tue Mar 27, 2012 3:57 pm ]
Post subject:  Re: Positively charged petrol tank
That doesn't sound good :? Lol
Any ideas on what would cause this ?
Author:  Gwagensteve [ Tue Mar 27, 2012 7:11 pm ]
Post subject:  Re: Positively charged petrol tank
Make sure the tank is grounded to the chassis.

Make sure the negative wire to the Make sure the chassis is connected to the battery.

There should be no charge on a fuel tank.

Steve.
Author:  just_cruizin [ Tue Mar 27, 2012 7:12 pm ]
Post subject:  Re: Positively charged petrol tank
Short in the fuel sender
Author:  Gwagensteve [ Tue Mar 27, 2012 7:20 pm ]
Post subject:  Re: Positively charged petrol tank
Might be true, but if the tank was properly grounded to the chassis then you'd get no charge showing on the tank and a blown gauge fuse or similar.

Steve.
Author:  sleeperzook [ Tue Mar 27, 2012 7:32 pm ]
Post subject:  Re: Positively charged petrol tank
This might be an insulting question but you mentioned you're using test light correct? Any chance your reference wasn't/isnt infact a positive supply and you're seeking earth through the tank?

Obviously with a test light it only indicates a potential difference in voltage and hence current flow but without an indication of polarity. The other question i instantly had was 'how bright was the test light?". The reason I ask it is possible your tank is poorly earthed and by putting the test light between it and your chassis/body you are creating either an earth or parallel circuit to ground. I'd say use a multimeter to determine polarity, check all your earths (ie resistance between panels/chassis/tanke etc should be low, ie single digit ohms) and if that doesnt sort you out, pull fuses one at a time to attempt to isolate the feed.

Hope this helps.
Aaron
Author:  JrZook [ Tue Mar 27, 2012 9:49 pm ]
Post subject:  Re: Positively charged petrol tank
Imma verging with sleeper zook here.

The only way the tank could be actually positively charged is if the sender supply or fuel pump supply is shorted to the tank and then the tank was insulated to the chassis which I find very hard to believe. You need to adhere to both conditions simultaneously for this to happen. In this case you would have had some fuses blown by now.

Now exactly how did you come to this conclusion? What were the test light probes connected to?
Author:  jdk81 [ Wed Mar 28, 2012 5:05 am ]
Post subject:  Re: Positively charged petrol tank
As said before, ensure there is an earth wire between the chassis and body.

My fuel tank guage was sporadic, and my LED tail lights flicked, the standard lights didnt.

Found out it was a poor earth between the chassis and body.
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