tumor21

So driving my '87 extra cab 22re 5spd down the road last night, didn't see a pot hole and hit it pretty good... enough to wake me up for sure. As soon as that happened, my fuel gauge that was saying half a tank... dropped instantly to nothing. I pulled over and double checked that there was no massive puddle under my truck and that i wasn't dragging my own fuel tank behind me or anything. There is no abnormal gasoline smell at all and the truck runs and drives normally. I'm thinking it's something to do with the sending unit.

When I park the truck and let it sit for a while, the fuel gauge needle with no power drops below the last line all the way to the bottom of the gauge. When I start it up, the needle moves up to the bottom fuel level line and just sits there. Any Ideas on where to start?

toyotacharles

that almost sounds as if needle in gauge dropped below min marker pin and is still reading just very low from where it should be. i suspect gauge in dash to have messed up by the bump. and dang what a bump in the road

tumor21

I was a hell of a pot hole, I will say that. So I'm guessing I'll have to rip open my gauge pod then? If it's a problem with just where the needle is leveled, then I would guess if I fill up, then the needle should still rise up higher than where it is? hmmm, may have to test that one at the pumps on my lunch break

Hadmatt54

Is everything else electrical in the cluster working properly? Tach, temp, etc.

tumor21

Everything else is working properly. Temp, etc...

tumor21

So I ran to the gas station on my break and did a little test...
This is what the gauge looks like right when i pulled in at the pump:



Now here is 4 gallons later:



I'm not seeing much of a difference. Especially a 4 gallon difference. Here is a video of what I see each time I start it or at least turn the key to acc. The needle goes to the bottom line and then stops no matter how much fuel is in the tank. Sorry the video cut off before it actually (finally) goes up to the last line but my phone ran out of space on the memory card while filming:

scuba

I'd pull the pump bracket out of the tank and verify that the float is still connected to the sending unit.

xxxtreme22r

also don't assume the sender is bad, I wound up fooling with mine only to find out the connectors on the top of the sender were rusted out. Took it apart re-soldered it and it now works.

Hadmatt54

Sending unit is not part of the pump bracket, it's seperate on the rear part of the tank.

sb5walker

If the fuel gauge works when tank is near full, and then drops to zero when fuel drops below a certain point, then it's the sender. If not, it's more likely to be a connection problem.

https://www.yotatech.com/forums/f116...runner-199822/

MudHippy

My 88 does this exact same thing sometimes. I first noticed it several years ago while hauling ass down a steep, washboard, potholed gravel road. Hit a decent size pothole about midway and then, "OH CRAP! I thought I had more gas than that!". Did the same as you, pulled over and checked for leaks. Nothing. "Huh? That's wierd"."Must be the sending unit".

Got back in and continued down the road. Then BAM! I hit another good one at the bottom. Gauge shot right back up to the 1/4 mark where it should've been.

Anyhow, it does it every so often to this day. Things I've noticed that are worth mentioning are:

1. Only does it when I've got ~1/4 tank or less.

2. Usually after a hard bump in the road, sometimes from getting tilted off-camber steeply(wheeling/off-road), rarely for no apparent reason at all.

3. The needle on the gauge doesn't always fall. Sometimes it sticks where it was, or just slightly above, and doesn't fall. Leaving me to think I had more gas than I did. Thank you low fuel warning light! YES, it works w/o the gauge...somehow...trust me.

4. The only 3 methods of "unsticking" that I've found are:

A) Hit another good sized pothole. 50-60% effective.

B) Whack the bottom of the tank/skidplate with the heaviest object available. 50-60% effective.

C) Get gas. I'm sorta suprised that didn't work for you, it works for me 80-90% of the time. Sometimes it takes awhile afterwards. Never has it stopped working on me for an entire tank's worth of gas run through it.

Give it some time.

EDIT: Why is it happening? The float in the tank gets stuck(you tell me why?). Where it's stuck, is what the gauge is telling you. That much I do know.

Hadmatt54

Here is what the sending unit looks like. This one is an SR5 with a 3 wire connector and a low fuel level switch, that is what the silver canister is. The sending unit is a glorified variable resistor, it consists of a stationary coil and a moveable wiper arm that is attached to the float. The item at the bottom of the picture is what the coil looks like.
[IMG][/IMG]
After connecting an ohmmeter across the two outside wires of the gauge wiring, according to the FSM the fuel guage should have a resistance value of 3 ohms(+2 or -3) when full. This one is 2.1 ohms.
[IMG][/IMG]
At empty the gauge should read 110 (+ or - 7.7 ohms) This one is right there.
[IMG][/IMG]

The float moves so easily I doubt that it could stick in its normal range of motion, unless there is something in your tank that shouldn't be there! It could stick if it was a 19 gallon sending unit in a 17 gallon tank. The float arm is longer, so at empty it would still show fuel. Open turns in the coil are a possibility also! The sending unit completes a circuit through the wiper arm. Once the wiper arm drops below the break in the wire turns the circuit is broken and the fuel gauge stops working.
That spare coil in the picture came out of a 4Runner, the unit rusted pretty much apart, but the coil was intact. Most problems are usually wiring!

yotarover

for the guys who are having the same problems..