2008 Tacoma Fuel Gauge Only Reads 3/4 Full

I've searched this forum and the googlewebs but don't seem to find any info that might help me with my issue.

Since I got this truck a year ago, the fuel gauge only reads 3/4 when the tank is full. The prior owner said it always did that for him also as long as he owned it. It drops smoothly and the low-fuel light comes on long before the tank is empty.

So I thought "fuel sending unit" and got the part. But in searching around, I've been reading about 4Runners having similar issues due to a bad ground for the sending unit.

Yesterday I removed the bed bolts in preparation to replace the sending unit. But before I proceed further, I'd like to check this ground and/or measure what the fuel gauge is reading at the gauge itself.

I'd also like to know if there is a fuel gauge "reset" procedure for the Tacoma? If so, I would like to try this as well. I really would like to avoid replacing the sending unit if it is not the culprit.

Many thanks if any of you guys have any thoughts on this.

 

You can short terminals 2 and 3 at the pump together briefly and verify that the gauge reads full, there is no "reset" for the fuel gauge.

 

After looking at the specification sheet I can tell you that a corroded connection/terminal/bad ground will indeed cause the gauge not to read at the full mark. The more electricity that passes at the fuel gauge the more magnetism, the more magnetism the more movement to full. Clean the connections/terminals and grounds to lessen the resistance. You just might correct your problem.

 

Thank you so much Dm93. With pins 2 and 3 shorted, the gauge goes all the way to full.

So that appears to confirm that the sending unit is bad, yes? I guess I will now (tomorrow) pull the fuel pump and replace the sending unit.

 

I would like to check the ground for sure. I'll have to eyeball things and try and locate where it is.

Thank you USMILRET.

 

Ok so I checked the resistance range of the new sending unit, and it was right on the money.

I then filled the tank (gauge read 3/4 of course) and then I measured the resistance of the sending unit at the fuel pump connector. Instead of something like 5 ohms, it was 27 ohms - which would correlate with the gauge reading 3/4.

That confirmed that the sending unit was the culprit, so I proceeded to pull the fuel pump to change it. When I pulled it out, I was surprised to see the shape (literally) that it was in.



When this truck was new, it was t-boned hard on the passenger side - and totaled. The person I bought it from had it repaired. They did a decent job straightening the frame etc. But apparently the gas tank had been damaged and replaced as part of the repair - but instead of replacing the also-damaged (bent) fuel pump, they just put it into the new tank - and it actually worked fine. The issue is that it was bent at such an extreme angle that the float for the sending unit physically could not travel fully to indicate full.

This is not what I expected to find for sure!