68 GMC Sierra fuel gage/electric - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Captain J · 12-20-2018, 09:00 AM

Greetings
1. My friend’s 1968 GMC Sierra fuel gauge is not working, I checked the wire from sending unit to the fuse box it was good, however the wire connection to the fuel box have no electricity at all (it plugs to the top of the fuse box it indicates fuel gauge)
Anyone knows why no electricity and how to check/fix/resolve it?

2. As I know, the 1968-1972 sending unit has only one fuel port that goes to the fuel pump, this truck has 2 ports, one is venting hose, however it’s inside the cab, and cab smells fuel.
Do I cap it, or do I extend the hose to outside and where?

Note: this truck is fully restored.

Thanks

**HO455** · 12-20-2018, 01:13 PM

This should get you through your fuel guage issue.

http://67-72chevytrucks.com/vboard/s...d.php?t=640615

I am not much help with the fuel port, except to encourage you to do a search using the box above. I know there are lots of threads about this. Year and whether it was a California truck make a difference too.
Good luck.

Captain J · 12-21-2018, 11:12 PM

HO455, thanks for your help

**special-K** · 12-22-2018, 07:15 AM

Just so you know, there was no such thing as a GMC Sierra in '68. That trim package came along later.

hugger6933 · 12-22-2018, 11:34 AM

The sender with two ports is for a 72 if I remember correctly that extra would go the the purge canister witch you don't have . BUT if you have the right gas cap for your year it is vented and then if that indeed is the case you can plug that port with a vac cap no problem. Jim

Captain J · 12-23-2018, 10:29 AM

Quote:

Originally Posted by special-K

Just so you know, there was no such thing as a GMC Sierra in '68. That trim package came along later.

Thanks for info,
This one has Sierra Grande on the side, and on the glove compartment,

**Sheepdip** · 12-23-2018, 10:48 AM

The wire to the top of the tank is a ground wire, the 12 volts comes into play behind the dash at the gauge and to the fuse panel.

Captain J · 12-23-2018, 12:35 PM

The problem is that no indication at the fuel gage, the fuse beside where the Tan wire (coming from sending unit) is not workin. My knowledge this wire your taking about (on top of sending unit) should be the 12v, sending unit is grounded by the tank.
Temp gauge is moving slightly when engine is idling

Captain J · 12-23-2018, 12:39 PM

Quote:

Originally Posted by hugger6933

The sender with two ports is for a 72 if I remember correctly that extra would go the the purge canister witch you don't have . BUT if you have the right gas cap for your year it is vented and then if that indeed is the case you can plug that port with a vac cap no problem. Jim

I’ve a 72 and it only has one port,
For this truck, I’m not sure about fuel cap.

**Sheepdip** · 12-23-2018, 03:49 PM

Quote:

Originally Posted by Captain J

The problem is that no indication at the fuel gage, the fuse beside where the Tan wire (coming from sending unit) is not workin. My knowledge this wire your taking about (on top of sending unit) should be the 12v, sending unit is grounded by the tank.
Temp gauge is moving slightly when engine is idling

Nope it's a ground wire, the tank to the body just completes the grounding circuit. The negative feed from your battery to the sending unit in this illustration is completed by your metal tank to the cab/body, the wire from sender to gauge is a continuation of that grounding to complete the grounding circuit.

https://auto.howstuffworks.com/fuel-gauge1.htm

12-20-2018, 09:00 AM	#1
Captain J Registered User Join Date: Nov 2017 Location: H, Q Posts: 180	68 GMC Sierra fuel gage/electric Greetings 1. My friend’s 1968 GMC Sierra fuel gauge is not working, I checked the wire from sending unit to the fuse box it was good, however the wire connection to the fuel box have no electricity at all (it plugs to the top of the fuse box it indicates fuel gauge) Anyone knows why no electricity and how to check/fix/resolve it? 2. As I know, the 1968-1972 sending unit has only one fuel port that goes to the fuel pump, this truck has 2 ports, one is venting hose, however it’s inside the cab, and cab smells fuel. Do I cap it, or do I extend the hose to outside and where? Note: this truck is fully restored. Thanks __________________ 1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454

12-20-2018, 01:13 PM	#2
HO455 Post Whore Join Date: Feb 2016 Location: Portland Oregon Posts: 10,787	Re: 68 GMC Sierra fuel gage/electric This should get you through your fuel guage issue. http://67-72chevytrucks.com/vboard/s...d.php?t=640615 I am not much help with the fuel port, except to encourage you to do a search using the box above. I know there are lots of threads about this. Year and whether it was a California truck make a difference too. Good luck. __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban the WMB,1991 S(stink)-10 Blazer,1969 GTO, 1970 Javelin, 1952 F2 Ford 4X4, 29 Model A, 72 Firebird. 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377

12-21-2018, 11:12 PM	#3
Captain J Registered User Join Date: Nov 2017 Location: H, Q Posts: 180	Re: 68 GMC Sierra fuel gage/electric HO455, thanks for your help __________________ 1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454

12-22-2018, 07:15 AM	#4
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,862	Re: 68 GMC Sierra fuel gage/electric Just so you know, there was no such thing as a GMC Sierra in '68. That trim package came along later. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

12-22-2018, 11:34 AM	#5
hugger6933 Registered User Join Date: Oct 2008 Location: Marianna Arkansas Posts: 7,257	Re: 68 GMC Sierra fuel gage/electric The sender with two ports is for a 72 if I remember correctly that extra would go the the purge canister witch you don't have . BUT if you have the right gas cap for your year it is vented and then if that indeed is the case you can plug that port with a vac cap no problem. Jim

12-23-2018, 10:48 AM	#7
Sheepdip Senior Member Join Date: Nov 2018 Location: Waterford California Posts: 2,365	Re: 68 GMC Sierra fuel gage/electric The wire to the top of the tank is a ground wire, the 12 volts comes into play behind the dash at the gauge and to the fuse panel.

12-23-2018, 12:35 PM	#8
Captain J Registered User Join Date: Nov 2017 Location: H, Q Posts: 180	Re: 68 GMC Sierra fuel gage/electric The problem is that no indication at the fuel gage, the fuse beside where the Tan wire (coming from sending unit) is not workin. My knowledge this wire your taking about (on top of sending unit) should be the 12v, sending unit is grounded by the tank. Temp gauge is moving slightly when engine is idling __________________ 1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454



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