1970 C10 Fuel Gauge Works Intermittently - The 1947 - Present Chevrolet & GMC Truck Message Board Network

rmawyer · 06-26-2016, 07:14 PM

It was working intermittently - sometimes OK, sometimes showing empty. I replaced the fuel sending unit and since then the gauge only showed empty - until today when it worked fine (showed 3/4 full) for a short time before going back to empty. Seems like a short or grounding issue. What's a good next step? Replace the gauge? Thanks for sharing expertise.

custom10nut · 06-26-2016, 09:57 PM

Clean the contacts on the multi plug that connects your dash to the wiring harness. Condensation will cause all kinds wacky things with the gauges. It's a real easy fix with some contact cleaning spray. Hope this fixes it for you

Rich916 · 06-27-2016, 10:15 AM

I had the same problem, drove me nuts tracking down the issue.
I grounded the sending unite and everything works great.
Drill a small hole in one of the tabs and ground to the cab. The seat hides everything.

rmawyer · 06-27-2016, 05:11 PM

Thanks for the suggestions. I will try them in a couple of weeks when I revisit the truck at its home base in beautiful Hoopers Island MD.

mike16 · 07-08-2016, 03:06 AM

my gas guage worked intermitantly.... or so I thought.... then I realised my truck kept pointing to "E" because it was a gas hog. you cant fix that with a soldering iron

rmawyer · 07-11-2016, 07:56 PM

Thanks for the great suggestions. I got down to where the truck is located on Saturday and added the ground wire to the fuel sending unit. Had to remove seat to get to unit. The new ground wire corrected the problem - the gauge now works!

But here's a strange follow-up: my speedometer, that was showing speed too high (100 MPH at 50MPH), is now showing speed only slightly too high (60 MPH at 50). I can't figure out a link to the new ground I added. Maybe it's just a different symptom of a bad cable, transmission gear, something else?

On to the next problem. . .

mike16 · 07-12-2016, 11:48 AM

speedo cable might be ready to fail. also dry old grease can cause it to read irradically. pull the cable out of the housing and soak them both is solvent to clean and flush out ould grease and dirt. clean it good. then soak the cable in synthetic 30 wt motor oil and reinstall it.

if the cable is worn and has little wires poking out. its no good and both cable and houing should be replaced.

new cable should also be lubed with synthetic 20/30 wt oil

06-26-2016, 07:14 PM	#1
rmawyer Registered User Join Date: Jul 2015 Location: Fishing Creek, MD Posts: 49	1970 C10 Fuel Gauge Works Intermittently It was working intermittently - sometimes OK, sometimes showing empty. I replaced the fuel sending unit and since then the gauge only showed empty - until today when it worked fine (showed 3/4 full) for a short time before going back to empty. Seems like a short or grounding issue. What's a good next step? Replace the gauge? Thanks for sharing expertise.

06-26-2016, 09:57 PM	#2
custom10nut Registered User Join Date: Apr 2015 Location: East Tn (In the heart of the Smoky Mtns) Posts: 1,863	Re: 1970 C10 Fuel Gauge Works Intermittently Clean the contacts on the multi plug that connects your dash to the wiring harness. Condensation will cause all kinds wacky things with the gauges. It's a real easy fix with some contact cleaning spray. Hope this fixes it for you

06-27-2016, 10:15 AM	#3
Rich916 Registered User Join Date: Dec 2009 Location: Rancho Cordova, CA Posts: 274	Re: 1970 C10 Fuel Gauge Works Intermittently I had the same problem, drove me nuts tracking down the issue. I grounded the sending unite and everything works great. Drill a small hole in one of the tabs and ground to the cab. The seat hides everything. Attached Images __________________ 71 Short Step Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=429946

06-27-2016, 05:11 PM	#4
rmawyer Registered User Join Date: Jul 2015 Location: Fishing Creek, MD Posts: 49	Re: 1970 C10 Fuel Gauge Works Intermittently Thanks for the suggestions. I will try them in a couple of weeks when I revisit the truck at its home base in beautiful Hoopers Island MD.

07-08-2016, 03:06 AM	#5
mike16 Registered User Join Date: Dec 2009 Location: bisbee, arizona Posts: 1,529	Re: 1970 C10 Fuel Gauge Works Intermittently my gas guage worked intermitantly.... or so I thought.... then I realised my truck kept pointing to "E" because it was a gas hog. you cant fix that with a soldering iron

07-11-2016, 07:56 PM	#6
rmawyer Registered User Join Date: Jul 2015 Location: Fishing Creek, MD Posts: 49	Re: 1970 C10 Fuel Gauge Works Intermittently - Corrected! Thanks for the great suggestions. I got down to where the truck is located on Saturday and added the ground wire to the fuel sending unit. Had to remove seat to get to unit. The new ground wire corrected the problem - the gauge now works! But here's a strange follow-up: my speedometer, that was showing speed too high (100 MPH at 50MPH), is now showing speed only slightly too high (60 MPH at 50). I can't figure out a link to the new ground I added. Maybe it's just a different symptom of a bad cable, transmission gear, something else? On to the next problem. . .

07-12-2016, 11:48 AM	#7
mike16 Registered User Join Date: Dec 2009 Location: bisbee, arizona Posts: 1,529	Re: 1970 C10 Fuel Gauge Works Intermittently speedo cable might be ready to fail. also dry old grease can cause it to read irradically. pull the cable out of the housing and soak them both is solvent to clean and flush out ould grease and dirt. clean it good. then soak the cable in synthetic 30 wt motor oil and reinstall it. if the cable is worn and has little wires poking out. its no good and both cable and houing should be replaced. new cable should also be lubed with synthetic 20/30 wt oil



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