sending unit issue

[MrLimo]

Hey all, thanks for reading. I'm new to this forum, and new to the world of the 60-66 GMC/Chevy (Notice the GMC first?) world! Purchased one recently and it's gonna be a slow build, but I'll start a thread with some photos so you all can see.

I have an initial question for everyone tho, as it has me a bit stumped regarding the fuel system.

66 GMC truck (I believe it's a C1000) has the original gas tank, sending unit and gauge. When I bought The beast, gas gauge did not work. Figured I'd buy a new gauge and sending unit to replace what was factory. After investigating, realized the fuel line comes out of the mount for the sending unit, so I decided to see if I could fix what was there. Pulled the sending unit from the tank & saw that the flat "wire" that connects to the outside of the sending unit was broken. Soldered a new one on the end of the flat 'wire' that's factory, and attached it to a new screw sticking out of the top of the unit and it works! Great, can see how much gas I have so I don't run out (had already done it twice at that point!), but come to find out it actually works intermittently. No rhyme or reason as to why, just sometimes it registers the amount of gas, and other times it's pegged at Full.

Any suggestions?

Thanks!
Chris

[MrLimo]

Anybody? Any ideas?

[1963c-10]

Grounding issue. Check the ground from the tank to the cab wall and make sure the guage is grounded good.

[MrLimo]

Thanks C-10. I did check the ground from the tank to the cab & that seems to be pretty good, but I didn't think to check the gauge. I'll do it today when I get home.

[1963c-10]

The guages are grounded throug the cluster housings. I would suggest adding a ground from the guage to the cab or firewall

[1963c-10]

Also check to make sure the sending unit wire is tight into the fuse block. It plugs in at the bottom left of the fuse block

[MrLimo]

Thanks for that one too. I'll check it today too.

Limo

[kieth]

To check the gauge itself disconnect it from the fuel sender, add 12 volt power and then ground the lead that goes to the tank. If the gauge goes to full when grounded then it is ok. If it does not move (like mine then the gauge is bad...... Kieth

[ol_skool_chevy]

I did the same thing once to mine.....and come to find out..your not suppose to weld or Solder on sending units.....it burns the element out and it HAS to be replaced....I replaced mine and works great now..

[MisterC]

I had almost the same scenario when I bought mine. Ultimately, I found the sending unit to be intermittent. I replaced it and have never had a problem since.

[MrLimo]

Originally Posted by ol_skool_chevy

I did the same thing once to mine.....and come to find out..your not suppose to weld or Solder on sending units.....it burns the element out and it HAS to be replaced....I replaced mine and works great now..

So, I took the sending unit apart, and the contact inside seemed to be a bit dirty and corroded. I cleaned it up, put it back and it seems to be OK now. At least I know for certain that it's not the gauge, or a ground at the gauge. I guess if it fails again, I'll try to find an OEM sending unit to replace what's there.

[MrLimo]

Originally Posted by MisterC

I had almost the same scenario when I bought mine. Ultimately, I found the sending unit to be intermittent. I replaced it and have never had a problem since.

Were you able to find an OEM sending unit?

[MrLimo]

Thanks to all who looked, I appreciate it. I did take the sending unit apart, cleaned it up inside, made sure that it appeared to be making good contact and it's working! Works 100% of the time when it's not in the tank, then I'd put it back in the tank and it wouldn't want to work. Removed it a couple of times fidgeting with this & that, and now it appears to be working. I still think there may be a grounding issue, but I'm not 100% sure. For now it works, who knows what tomorrow will bring!

[MisterC]

The sending unit I found is not OEM. I found the Spectra Premium FG119A Sending Unit on the Autozone site and then ordered it from Amazon at a significant savings.

[MrLimo]

Mister C, I went and found it at Amazon as well, if what I did doesnt take, I'ma buy it. Always like to try to fix it first, but this one may get the better of me!!

[70cst]

Here is a bump ...

Hey MrLimo ...
to the forum and from Ohio

[RoyL]

Originally Posted by MisterC

The sending unit I found is not OEM. I found the Spectra Premium FG119A Sending Unit on the Autozone site and then ordered it from Amazon at a significant savings.

Sorry to highjack but is related to this sending unit above. Searched around and found no definitive answer on the issue of whether these sending units are 0-30 ohms or 0-90 ohms? I am working on a 1965 GMC and have read that the sending units changed in 1965 to 0-90.

the one in the tank is a 0-90 ohms, and needs replacing. Trying to make sure I get the right one.... The only sending unit I found that said what ohm range it was, was from Bob's Chevy Truck, it said 0-30.

[luvbowties]

Originally Posted by RoyL

Sorry to highjack but is related to this sending unit above. Searched around and found no definitive answer on the issue of whether these sending units are 0-30 ohms or 0-90 ohms? I am working on a 1965 GMC and have read that the sending units changed in 1965 to 0-90.

the one in the tank is a 0-90 ohms, and needs replacing. Trying to make sure I get the right one.... The only sending unit I found that said what ohm range it was, was from Bob's Chevy Truck, it said 0-30.

AFAIK, all the trucks thru 1966 use the 0-30 ohm units. Don't recall the site, but one of the on-line suppliers specifies this. If I find it shortly, I will reply back w/the link to help you "feel secure" this info is correct. HTH,
sam

[luvbowties]

Originally Posted by RoyL

Sorry to highjack but is related to this sending unit above. Searched around and found no definitive answer on the issue of whether these sending units are 0-30 ohms or 0-90 ohms? I am working on a 1965 GMC and have read that the sending units changed in 1965 to 0-90.

the one in the tank is a 0-90 ohms, and needs replacing. Trying to make sure I get the right one.... The only sending unit I found that said what ohm range it was, was from Bob's Chevy Truck, it said 0-30.

FOR STOCK FACTORY GAUGES: I guess we all are familiar with the name of Eckler's for parts--hence we maybe trust them. Look at this link & see for sure that our trucks from 60-66 all used 0-30 ohm sending units. Did not go to 0-90 ohms 'til 1967 on the trucks, even tho' GM cars changed earlier.

>> http://www.ecklerstrucks.com/chevy-t...1960-1966.html <<

Here's another supplier, Car Parts Discount, who shows specifically a 1965 GMC as having 0-27 ohm senders--I guess GMC was a tad more accurate & got it down to the "fine print", being more exact: their gauges prolly did not read beyond "F" when filled like our cheaper Chevies. Naturally, in the grand scheme, 0-27 is practically the same to such a circuit as 0-30 would be.

.....for GMC 1000-series (read their 0-27 ohm spec in description)
>> http://www.carpartsdiscount.com/auto...html?3593=2627 <<

...for GMC 1500-series: (read their 0-27 ohm spec in description)
>> http://www.carpartsdiscount.com/auto...html?3593=2627 <<

Hope some of this helps,
sam

[RoyL]

Originally Posted by luvbowties

FOR STOCK FACTORY GAUGES: I guess we all are familiar with the name of Eckler's for parts--hence we maybe trust them. Look at this link & see for sure that our trucks from 60-66 all used 0-30 ohm sending units. Did not go to 0-90 ohms 'til 1967 on the trucks, even tho' GM cars changed earlier.

>> http://www.ecklerstrucks.com/chevy-t...1960-1966.html <<

Here's another supplier, Car Parts Discount, who shows specifically a 1965 GMC as having 0-27 ohm senders--I guess GMC was a tad more accurate & got it down to the "fine print", being more exact: their gauges prolly did not read beyond "F" when filled like our cheaper Chevies. Naturally, in the grand scheme, 0-27 is practically the same to such a circuit as 0-30 would be.

.....for GMC 1000-series (read their 0-27 ohm spec in description)
>> http://www.carpartsdiscount.com/auto...html?3593=2627 <<

...for GMC 1500-series: (read their 0-27 ohm spec in description)
>> http://www.carpartsdiscount.com/auto...html?3593=2627 <<

Hope some of this helps,
sam

Same,
Awesome, thx! That settles it, there's conflicting info out there for sure . . .
Now for my sending unit, it has 90 ohms stamped on it, but it reads up to only about 38-40 ohms . . . put it back in and reads about right, I'll fill up today and see if it goes to full . . . Maybe it's not bad.
Thanks again! This forum is great!

Roy

Update: filled up and gauge reads full! It works, even though its stamped "90 ohm" on the sender itself...