Looking for info on the fuel gauge/sender unit electronics. As a long time boat owner i know mechanical fuel senders and guages can be tempermental and downright questionable. With that said, my H2 isn't off by too much (and at least it works). The pics show that usage (20.6) and refill to shut off were very close. I've been keeping track and it is always within about a half gallon. But as can be seen, guage is showing just about 5-6 gallons left (just over first mark which is 4 gallon mark) but should be between 1/4 and 1/2 mark to reflect 12 gallons which should be in it. When off, guage is a tad under the orange empty mark, and when full is a bit under the full, so perhaps it is a guage motor issue. Or sender voltage.

QUESTION IS - does anyone have or know of voltage check points i can look at to determine if the guage motor needs to be addressed?
TIA

 

See the attached image.... that is directly from the GM eSI system. Another thing you can do if you want, pull the cluster out, remove the lens, gently set it back in place. Use a dinner fork to remove the needle, put the needle back on where you want it to be (where you know it should be) with the vehicle level, engine running. Years ago I used to do this to correct tachs and speedos using GPS and or a reader to verify the correct value.

 

Excellent, thank you. Just what I was looking for. Appreciate the info, and a good idea on the possible gauge correction. Thanks again.

 

The F needle appears a bit off. My 3 only holds 23gal and I always fill up before it goes below 1/4! 15gal was the most I've been able to add and the needle goes beyond the F=20gal> F to E+3gal reserved. H2's hold 32gal so there's more reserve when the needle hits {{{E}}}

 

So if I understand you correctly, when the needle is on the E mark it isn't 0 gallons in the tank but rather 3-5 gallons actually in there? Meaning the float in the tank isn't actually sitting on the bottom but rather, at the end of its most negative travel, and there would actually be a certain amount of space below allowing X amount of gas to be in a "reserve". Thus, the marks on the Guage would not represent 0-8-16-24-32 (F), but rather some other numbers (E=3-5 gal) based on what GM decided would be a reserve? Perhaps the defining voltages weren't meant to be linear but rather more non-linear to get folks to fill up before the pump starts sucking from the sludge and gumming up the injectors. Hmmmm, interesting. Appreciate the feedback. Gives me more to consider. At least my current "concern" isn't a leak (water, lubricant), knock or other common H2 issue. Well, there are the dim/missing lights in the cluster but I don't do much night time anymore! 😁

 

Check the amount of gallons it takes to fill from 1/4 until the pump stops and subtract from 32gal.
I know my 3 tank holds 23gal, the lowest I ever got before fill was 1/4 which takes 15gal until the pump stops(the needle is above F) = 8gal in the tank @1/4.

 

I got ya. Hey, I'm grateful the dang thing works!! It is an H2 after all! LOL.

I usually top off around half or just below, and at the pictured fill up I had let it go lower than I usually do. Now I know that's my 12 gal left mark! I find the DIC gallons used to be quite accurate and thus do rely on that info. As a retired Electronics/Telecommunications Engineer I just obsess over the little things - like a gauge being accurate LOL. I mean the Volts are within +- 1 or 2, the Oil Pressure is pretty close, etc. And FEDS require the Speedo be programmed accurately, so I just wish the Auto Industry was as **** about Fuel gauges and ensuring they actually work to a simple standard, like 1/4 of a 20 gal tank means you have 5 gals left! My H3 Fuel gauge was like yours. My H2 barely hits F when topped up and sits a bit below the E when off. So I suspect it still comes down to a gauge motor not acting in tolerances with the actual sender voltages (which I have yet to check) or the needle is just off. Being how I need to address a few of the lights on the cluster, I'll either tinker, or outright replace all the motors & lights. Appreciate your info & chats. I'll update here if/when I can get to this little project now in the waiting. Thanks again ----

 

be carefull if considering doing LED bulb swap to the cluster if i recall there is one or 2 bulbs that if you put the led in the wrong way it will fry the cluster.
also if you put too much heat on the stepper motor pins it can lift the trace pads or tear them off the board wich will require micro soldering jumper wires if too damaged. some holes are double sided so might tear traces on 2 sides.

 

Will do. Thanks.