Bad Fuel Sending Unit? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Feldsine · 08-06-2010, 07:05 PM

Hello folks.

I have read all the posts I can find to try and fix my frozen gas gauge, and I'm happy to say that it appears to have been a rusty gauge cluster fuse, the gauge started to move after I reseated the fuse.

At this point, I can remove the fuel gauge connector at the fuse box, and ground the tab, and the gauge swings to empty, good so far.

When I remove the ground from the tab, the gauge swings to the 3 oclock position, about an inch too far. It does the same with the fuel sender wire connector attached to the fuse box tab. There is probably a little over 3/4ths of a tank of gas while I'm checking this.

Can one of the experts confirm my diagnosis that this is in fact, a bad sending unit?

JimKshortstep4x4 · 08-06-2010, 08:07 PM

It sounds like it could be the sending unit but if the wire is broken you will have the same results. If you have an ohm meter check the reading of the sender between the pin and the tank. It should read between 0 ohms and 90 ohms. (In your case 3/4 of a tank would translate to approximately 68 ohms).

If you get a high reading then the tank unit will need to be replaced.

Jim

Feldsine · 08-06-2010, 08:36 PM

Jim, thanks for the advice, I'll try that tommorrow AM and let you know the results.

Feldsine · 08-07-2010, 03:01 PM

Ok, I put a clip on the post that the wire connects to, and touched the other lead to the gas tank, and the reading was OL, open. I'll go ahead and order a sender.

Legolas894 · 08-10-2010, 11:00 PM

I'd take the sender out of the tank and confirm the ohms reading by manually moving the float up and down. My original one had the coiled wire broken. Then I got a used one and it had rough spots so it would jump around when the float was moved up and down.

They come out pretty easy (just no smoking when you're doing it!)

Feldsine · 08-10-2010, 11:04 PM

Thanks, I've got a new one from LMC on order, but I'll check the old one before I put the new one in. I'll post the results here when I'm done, part should arrive in a couple days.

Legolas894 · 08-10-2010, 11:09 PM

Quote:

Originally Posted by Feldsine

Thanks, I've got a new one from LMC on order, but I'll check the old one before I put the new one in. I'll post the results here when I'm done, part should arrive in a couple days.

Let us know how it looks/works. I'm going to be ordering a new one so I can stop running out of gas!

08-06-2010, 07:05 PM	#1
Feldsine Registered User Join Date: Nov 2007 Location: Eureka, CA Posts: 60	Bad Fuel Sending Unit? Hello folks. I have read all the posts I can find to try and fix my frozen gas gauge, and I'm happy to say that it appears to have been a rusty gauge cluster fuse, the gauge started to move after I reseated the fuse. At this point, I can remove the fuel gauge connector at the fuse box, and ground the tab, and the gauge swings to empty, good so far. When I remove the ground from the tab, the gauge swings to the 3 oclock position, about an inch too far. It does the same with the fuel sender wire connector attached to the fuse box tab. There is probably a little over 3/4ths of a tank of gas while I'm checking this. Can one of the experts confirm my diagnosis that this is in fact, a bad sending unit? __________________ Stan Feldsine - Build Thread - http://67-72chevytrucks.com/vboard/s...d.php?t=673856 1969 C10 LWB Fleetside - 350 - 700R4 1971 C20 LWB Fleetside - 350 - TB350

08-06-2010, 08:07 PM	#2
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: Bad Fuel Sending Unit? It sounds like it could be the sending unit but if the wire is broken you will have the same results. If you have an ohm meter check the reading of the sender between the pin and the tank. It should read between 0 ohms and 90 ohms. (In your case 3/4 of a tank would translate to approximately 68 ohms). If you get a high reading then the tank unit will need to be replaced. Jim __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

08-06-2010, 08:36 PM	#3
Feldsine Registered User Join Date: Nov 2007 Location: Eureka, CA Posts: 60	Re: Bad Fuel Sending Unit? Jim, thanks for the advice, I'll try that tommorrow AM and let you know the results. __________________ Stan Feldsine - Build Thread - http://67-72chevytrucks.com/vboard/s...d.php?t=673856 1969 C10 LWB Fleetside - 350 - 700R4 1971 C20 LWB Fleetside - 350 - TB350

08-07-2010, 03:01 PM	#4
Feldsine Registered User Join Date: Nov 2007 Location: Eureka, CA Posts: 60	Re: Bad Fuel Sending Unit? Ok, I put a clip on the post that the wire connects to, and touched the other lead to the gas tank, and the reading was OL, open. I'll go ahead and order a sender. __________________ Stan Feldsine - Build Thread - http://67-72chevytrucks.com/vboard/s...d.php?t=673856 1969 C10 LWB Fleetside - 350 - 700R4 1971 C20 LWB Fleetside - 350 - TB350

08-10-2010, 11:00 PM	#5
Legolas894 Chemist under the hood... Join Date: Apr 2009 Location: Fort Erie,ON, Canada Posts: 617	Re: Bad Fuel Sending Unit? I'd take the sender out of the tank and confirm the ohms reading by manually moving the float up and down. My original one had the coiled wire broken. Then I got a used one and it had rough spots so it would jump around when the float was moved up and down. They come out pretty easy (just no smoking when you're doing it!) __________________ Current fleet: 2013 GMC Sierra, 5.3L, 4x4 1988 GMC Sierra, 305, Auto 1984 Jeep Grand Wagoneer, 360 V8 1997 VW Cabrio, 2.0L 2017 Toyota Rav4, 2.5L Stuff I wish I still had: 2013 Toyota Matrix [RIP] 1967 GMC 910 Fleetside, 283 V8 [1st Love-SOLD] 1987 Jeep Cherokee Laredo 4X4, 4.0 I-6 [SOLD} 1994 Chevrolet Caprice Classic, 5.7LV8 [SOLD] 1995 Chevrolet Astro AWD, 4.3L V6 (RIP) 1998 Chevrolet Suburban 4x4, 5.7L V8 [SOLD]

08-10-2010, 11:04 PM	#6
Feldsine Registered User Join Date: Nov 2007 Location: Eureka, CA Posts: 60	Re: Bad Fuel Sending Unit? Thanks, I've got a new one from LMC on order, but I'll check the old one before I put the new one in. I'll post the results here when I'm done, part should arrive in a couple days. __________________ Stan Feldsine - Build Thread - http://67-72chevytrucks.com/vboard/s...d.php?t=673856 1969 C10 LWB Fleetside - 350 - 700R4 1971 C20 LWB Fleetside - 350 - TB350



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