Gas Gauge Check

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Date: Sun, 04 Jan 1998 15:01:25 -0600
From: breeze@cysource.com (Jeffrey Delzer)
Subject: Gas gauge problem
To: Toy4x4@tlca.org

Brian T Engle wrote:
> 
> I have a problem with my gas gauge. For some reason when the tank is
> full it reads 3/4 of a tank, and when the tank gets down to 1/4 full on
> the gas gauge, I only put in about 1/2 a tank of gas. I don't think the
> floater has absorbed too much, because it just happened all of a sudden.
> One day I was driving and I had a full tank, the next day I had 3/4 of a
> tank. Is there a problem with the connection between the floater and the
> gas gauge, or is the problem inside the gas tank? If it's outside of the
> gas tank, how do I fix it? Oh yeah, in between when the gauge worked and
> when it went all funny, I installed a roll ber that mounts right behind
> the cab and may have just smacked the linkage into a weird psoition. If
> any one has had any expriences with anything like this, please help.
> 
> Brian Engle
> 1990 Toyota Xtra Cab

Brian,

First of all, is your tank physically damaged and dented, not allowing
the sending unit to travel through its full arc? Secondly, the wiring
harness containing the gauge wire travels from the right side of the top
surface of the tank, along the right frame rail until it's directly
under the passenger seat, then through a grommet into the cab. Check
that harness for chafing and damage, especially since you just did some
work around there with the roll bar.

You can help to pin this down by temporarily isolating the gauge from
the sending unit. Assuming the color codes and wire harness locations
haven't changed from 1990 to '94, there'll be a harness (and connector)
under the carpet directly under the passenger seat. One of those wires
is Yellow/Red, (yellow with a red stripe). That wire goes from the
sending unit to the gauge. To simplify, if that wire is Grounded the
gauge reads Full, and if that wire is Open the gauge reads Empty.

So after pulling that connector apart, turn the Ignition "On" and wait a
few minutes while you watch the gauge move as far as it's physically
capable of moving toward the Empty mark. Once you're satisfied with
that, ground that Yellow/Red wire for a few minutes with the Ignition
still "On". (Do this on the "gauge" side of the connector, toward the
front of the vehicle, obviously. And don't try to start the engine, it
can't start with this connector pulled apart.) Your gauge will move
toward Full as far as it's physically capable of moving. Give it enough
time to get there, just as you would after filling a completely empty
tank and watching the gauge slowly come up to the Full mark.

If the gauge responds normally, then the problem is in the sending unit
or associated wiring rearward from that connector. My money would be on
a binding sending unit.

Jeff Delzer

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Date: Sun, 04 Jan 1998 16:14:27 -0500
From: Darren Floen 
Subject: Gas gauge problem
To: Toy4x4@tlca.org

Check for a bad ground at the guage and at the fuel tank.

Darren

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