Fuel Sending Unit

[P Nolan]

Alright the gauge sits on full, Ill be honest i have never seen that, normally see a busted unit sit on E. Everything I have researcherd tells me to replace the fuel sending unit gotta ask am I going in the right direction? Also if yes when I drop the tank to replace it am I looking at any additional steps that would be recommended to do while its out?


Thanks

[shamanie]

P Nolan, my sending unit is busted too. It sits on a 1/4 when full. Then slowly goes down as I drive. So in essence, a 1/4 of a tank is full, and a 1/4 of a 1/4 of a tank is actually a 1/4 of a tank. Got that, good. smile.gif

So for it to read full may not be that strange considering where mine decided to die. By the way, where are you looking to get yours? I think I saw one in my LMC truck catalog.

The only other thing I could add, which you probably already know, is to have a good look see in the tank for debris and corrosion. Last thing a guy needs is sediments in the feul tank waiting to be sucked up into the fuel lines.

L8r.

[P Nolan]

I looked locally first and found Napa for $60 and thats ordered 5-6 days. Im trying to move in the direction of using known vendors recommended from other members. If I have to order it I would prefer direct and a few extra bucks doesnt bather me for a part from reputable source.

Since this is an older model fuel sending unit doesnt it work on the concept of current resistance? so the float would have to be stuck at the top right?

[DmaxMaverick]

When the sender failed on my '85, it was exactly like shamanie's. Only the E to 1/4 worked, but worked linear. 1/4 was full, 1/8 was half, and E was still E. I'm the only one that drives it, so I never fixed it. Honestly, it's more accurate than it has ever been, only the needle is in the wrong place. I have the large fuel gage, so it's easy to read. One of these days, I'll get around to it.

When they fail, it's usually shorted, or open. Shorted will show F, and open will show E. Either way, broke is broke.

[john8662]

For the gauge that reads 1/4 when full there is a fix without replacing the gauge. The resistor on the back of the gauge (looks like a flat chalk stick made of porcelain) is burned out. I found a local aftermarket GM store that sold a "fix-a-gauge" kit that had a normal looking resistor (that was painted) with enough pig-tail wire to connect where the old resistor was. My 86 pickup did this one day, took me a week to figure it out, and that was the problem, I've done a few of them now. I think the cost of the resistor is under 10, quite a bit cheaper than replacing the whole unit.

You can buy em here:

http://www.fix-a-gauge.com/

[P Nolan]

Wouldnt bug me so bad if it was atleast useable. If I was very familiar owner of my truck I would know my per tank milage I watch that on my gassers tells me how they are doing. But since I just purchased this one I have no Idea I should get out of a full tank.

With a short being mentioned could it be a disconnect or a fuse? (stabs in the dark)

I just dont want to have to kick out $60 on a unit til 1) it totally goes out or 2) When its time on the to do list comes up.

[DmaxMaverick]

Thanks John!!

Found it on the diagram. The diagram doesn't show the value of the resistor, so hopefully it'll be marked. Should be a Radio Shack item, probably 29

[BobND]

Originally posted by P Nolan:
Alright the gauge sits on full, Ill be honest i have never seen that, normally see a busted unit sit on E. Everything I have researcherd tells me to replace the fuel sending unit gotta ask am I going in the right direction? Also if yes when I drop the tank to replace it am I looking at any additional steps that would be recommended to do while its out?


Thanks The fuel gauge on a Chevy of this vintage will go to full if the gauge sender wire to the tank is "open" or the tank is not grounded, or the resistance wire in the sender is broken.

Many other fuel gauges will go the "E" if there is an open circuit, but this GM sytem will go to full, or even a little beyond.

There is a simple test to see if the gauge is good, and the wire is good back to the tank. Simply jumper the sender wire at the tank to a KNOWN GOOD ground, and the gauge should read "E".

If you jumper the wire at the tank to ground, and the gauge drops to "E", a bad sender (or sender ground) is indicated.

If you jumper the wire at the tank to ground, and the gauge remains at "F", it is a gauge or wiring problem.