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Technical => Electrical Tech => Topic started by: Master_xzavior on December 28, 2004, 06:33:09 PM

Title: fuel sending unit question
Post by: Master_xzavior on December 28, 2004, 06:33:09 PM
hey guys and gals quick question. will the fuel sending unit from an 85 fully digital dash work in an 87 with a fully digital dash? Someone had mentioned they have different resistance, but I know with the base digital cluster theyre the same between the years. Would it work if I used the unit from an 85 in my 87? Thanks in advance.
Title: Re: fuel sending unit question
Post by: jcassity on December 28, 2004, 07:27:36 PM
from what i can see here on FoMoCo manual 33-20-3 , the the actual resistance of the sender should be a 8-86 ohms empy/full respectivly on a sender with a conventional **or** fully electronic cluster.

Its basically a two wire conn but on wire is a ground and obtains it fairly quickly in the circuit. 

id say if the resistances compare out by manually moving the float up to full and down to empty by hand,, they should proove out while in use.
Title: Re: fuel sending unit question
Post by: Master_xzavior on December 28, 2004, 07:53:23 PM
well see the thing is I dont have both units Im trying to find out before buying the other if it wont work I dont want to spend the money honestly my car really needs it in more spots then just this real real real bad but Im tired of guessing at how much gas I got and the reading empty when its full and showing 9 gallons in the tank when its empty is really getting old.
Title: Re: fuel sending unit question
Post by: Ifixyawata on December 28, 2004, 08:56:24 PM
There's a way to keep track of fuel usage without a guage.  I've been doing it for almost a year.  But, it only works if you can afford to fill the tank up once. 

1.)  Fill tank.
2.)  Reset Trip Odometer.
3.)  At around 250 miles you have from 1/8 to 1/4 of a tank (estimate on the safe side).
Title: Re: fuel sending unit question
Post by: Master_xzavior on December 28, 2004, 09:07:04 PM
ok so basically I should just get it and test it with an ohm meter against the one I have and if it dont work sell it on ebay?
Title: Re: fuel sending unit question
Post by: jcassity on December 31, 2004, 08:43:37 PM
Quote from: Master_xzavior
ok so basically I should just get it and test it with an ohm meter against the one I have and if it dont work sell it on ebay?


not exactly,, you dont wanna sell things to people on ebay that does not work. certainly you did not mean you would do that on purpose:brick:
Title: Re: fuel sending unit question
Post by: Master_xzavior on December 31, 2004, 09:24:06 PM
I meant if it isnt the one I need.
Title: Re: fuel sending unit question
Post by: softtouch on January 01, 2005, 03:05:25 PM
According to the '84 shop manual: The standard fuel gage sending unit and the electronic sending unit are different resistances.
However the reason your gage works backwards is the standard gage sending unit resistance increases as the tank empties and the electronic gage sending unit resistance decreases as the tank empties.