waskillywabbit

iTrader: (-1)

1988 4Runner 3.0 auto

Tank leaked so I dropped it and had it welded up and lined.
Pickup and pump looked fine

Gas gauge will read full on fill up
After fill up it seems to read ok for a while then next time you drive it zero
It will go back up if you slosh it but it won't stay.

I think that's everything relative.

Any ideas? Questions to diagnose?

:wabbit2:

sbagdon

Guessing that the fuel level sensor is outputing level by voltage level. Seeing references for some level sensors for 0-5v, calibrated to 0.25v empty to 4.75v full. So...

What's the volgage coming out of the fuel-level sensor?

Guessing it's 0v or 5v, not 0v to 5v. Also going to guess that the sender either needs to be removed and loosened up a bit, or this specific maintenance event ended it's service life (sometimes just taking it out and putting it back in again is the event to drive it past it's service life...).

waskillywabbit

iTrader: (-1)

Gas gauge read like this before and after it was welded up and lined.

:wabbit2:

sbagdon

No matter when it started, going with it's either the sender (level sensor), wiring, or receiver (gas gauge). Guess you can either put a voltage generator up to the body harness to see if the gauge moves correctly, or a multimeter up to the sender to see what voltage it's outputting.

Don't have a factory manual, so don't know the proper voltages for testing. Yet if you don't have a variable voltage generator, AA batteries at different voltages should let you build a voltage that tests well. If it's calibrated to 4.5v for full, three AA batteries should get you to around that value.

waskillywabbit

iTrader: (-1)

Resistance for testing of sender gauge.
Looking for someone who had a similar experience and discovered what their solution was in fact. I can pull it and test either/both.

:wabbit2:

sbagdon

Resitance? Figured it would be voltage.

This post says cleaning the contact area made it work:
http://www.toyotanation.com/forum/10...ml#post3221973

Hopefully someone will chime in with first-person experience.

Yet sounds that it's either going to require cleaning, or signal generation or measurement to identify the broken component.

92 TOY

gonna hook right on this one. Joe's is edzackary the same. reads full at fill-up and for about the 1st 1/4 tank then is just falls all the way down. we just watch the trip odometer and fill-up in the 200 to 230 range.

but since you are having the same prob....I will see what goes on here.

CyMoN

I just live with the fact that mine dose it but I also have a second sensor that turns on a fuel light when I have only 2 gallons in the tank.

my 86 doesn't have that ask me how I know

waskillywabbit

iTrader: (-1)

Sitting on empty today when I went to the gas station and put in 5 gallons, so it was half full but registered nothing. After it was registered full on the gauge. I'll pay close attention to when it falls to "E" again.

It's being squirrely for sure.

:wabbit2:

combatcarl

How'd the winding on the gauge sender look? Mine did that, and looked ok, but when I pulled it out, and fiddled with it, the wire just unraveled off part of it. So it works til about 5/8ths of a tank, then its all over the place, til about 1/2. Then it usually just bottoms out.

waskillywabbit

iTrader: (-1)

I'll have to pull the tank when it gets the SAS/lift anyway so I'll check it then.

:wabbit2:

slow-mo

On my 22R, many, many, many years ago, my gas gauge would read full, when it was. Then once it would get to about the half-way mark, it would drop to the engine off position, even though I still driving it. I replaced the fuel sending unit in the gas tank and all is fine.

Even though I think all these years, maybe 15 years, the parts gut at Toyota gave me the shortbed sending unit. When the gauge shows nearly empty, I can only put 10-11 gallons of gas in the tank. I seriously doubt I have a 7 gallon reserve.

James Woods

iTrader: (1)

I have seen on other makes where the contact that the float sweeps on was scratched or dirty in one spot and reads open with ohm meter on that spot making the fuel gauge drop to zero although the tank is not empty.

combatcarl

Jealous! Wish I had funds and bits for an SAS!

wyoming9

iTrader: (1)

The sending unit is worn out or the corn whiskey your running in a 50/50 mix with gasoline has taken it`s toll.

once the sending unit wiper gets past the good section of resistor and on the section that is now open it gets no feed back so the gauge just drops to empty .

you know the gauge and wiring is good it is the sending unit that has failed.

I have one here someplace if you need pictures.

Perhaps you can still get a new one??

Is this yours or a victim ??

My 87 4runner has a issue about the same I bought a new sending unit here a few years ago it sits on a shelf with a extra clutch:jessica::jessica:

waskillywabbit

iTrader: (-1)

Filled up yesterday. Good for about 50 miles and it started being squirrely for another 10 miles. It would register up and down from 3/4 to nothing and back again.

Sounds like a bad sending unit. At least I think it can be pulled with little trouble and swapped.

Thanks for the feedback guys.

:wabbit2:

DeathCougar

iTrader: (23)

Sending unit for sure.

The FSM outlines the testing procedure, I can get that for you when I get home if you want.

OrRunner

iTrader: (1)

off topic sorry, But why do you have to pull the tank for your SAS? For welding in the rear spring mounts or???

waskillywabbit

iTrader: (-1)

Ordered new Toyota sending unit $145

Rear hanger mount on passenger side is right next to gas tank. 25 year old tank.

I prefer to remove the gas tank and not blow up and get dead.

:wabbit2:

OrRunner

iTrader: (1)

Yea, makes sense, I guess I thought there might be enough room to squeez in there, but I am definatly not a welder, but common sense would tell you to remove it I guess. Thanks for the reply!