70 Series Fuel Gauge anomalies

[Rigster]

Update to this thread... though the new fuel cap seemed to improve on the situation as read above, it would still act the same, just not as often. So far it looks like the new sender I put in the fuel tank has fixed the problem (so far it stays where the fuel level is without the odd fluctuations).

I will report back if this changes, but for those that might be experiencing similar issues that may be your issue as well. I can only surmise, that the aged senders get tired and don't function with any true level of accuracy? Even a broken watch/clock is correct twice a day?

 

[JDM Journeys]

Just in case someone is searching and comes across this thread, I am going to just add one more scenario, not likely same as your Darren, though I hope you'll indulge a slightly sideways post...
Mine acts pretty normal until I get to about 1/4 tank or so. At this point the guage starts hunting back and forth every so often, and seems to take the coolant temperature guage with it. I've read that there is a ground that gets less than effective behind the cluster and requires some very light sanding, but I haven't tried it yet.

Sounds like yours is solved @Rigster but for others out there with a wonky fuel guage...?

 

[Gun Runner 5]

Just in case someone is searching and comes across this thread, I am going to just add one more scenario, not likely same as your Darren, though I hope you'll indulge a slightly sideways post...
Mine acts pretty normal until I get to about 1/4 tank or so. At this point the guage starts hunting back and forth every so often, and seems to take the coolant temperature guage with it. I've read that there is a ground that gets less than effective behind the cluster and requires some very light sanding, but I haven't tried it yet.

Sounds like yours is solved @Rigster but for others out there with a wonky fuel guage...?

I believe the fuel and temp gauge share a common power source and ground. Would start with the ground.

 

[ATL Cruiser]

I dug into this pretty deeply when I pulled my tank last month. I found that the gage reads really well as long as you understand that the reserve tank still has 4-5gal below the bottom of the E line.

I cannot see how tank pressure could affect the readings at all. It's a toilet bowl float attached to a rheostat. Super simple device.

I think your sender is sticking along the rheostat. Put a new one in. It's easy from the manhole cover in the rear cargo area.

Fuel tank capacity / gauge calibration

Since I had my fuel tank out and drained, I decided to see how calibrated the fuel level sender was. Full tank is 23.8 gallons per everywhere. I started at 8 gallons: Essentially, I would say the fuel level gauge is properly calibrated at the top end with a spare "reserve tank" of...

forum.ih8mud.com

 

[Rigster]

I dug into this pretty deeply when I pulled my tank last month. I found that the gage reads really well as long as you understand that the reserve tank still has 4-5gal below the bottom of the E line.

I cannot see how tank pressure could affect the readings at all. It's a toilet bowl float attached to a rheostat. Super simple device.

I think your sender is sticking along the rheostat. Put a new one in. It's easy from the manhole cover in the rear cargo area.

Fuel tank capacity / gauge calibration

Since I had my fuel tank out and drained, I decided to see how calibrated the fuel level sender was. Full tank is 23.8 gallons per everywhere. I started at 8 gallons: Essentially, I would say the fuel level gauge is properly calibrated at the top end with a spare "reserve tank" of...

forum.ih8mud.com

Thanks ATL for the input. I did read your thread about when you pulled your tank, but ultimately yes, the new sender fixed it up.

My sender is actually two parts, a sensor on the end of a metal rod for low fuel/reserve light, and the fuel level float. The low fuel warning light worked as it was supposed to while the fuel would go up and down when it got to around 2/3 to half full through to empty.

It makes sense now that I realize it is actually 2 separate devices.

 

[OGBeno]

5 gals is the non-hybrid limit for all old Toyota vehicles.

Those with “low fuel “ indicators: This means you have about 5 gals of fuel left.

This indication has been the same for non-Hybrid vehicles for about 40 years.