Gas Tank question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

stingray72 · 11-03-2003, 11:02 AM

Ok guys.. I got a problem (and a headache). When I get in my truck in morning it smells like gas. I've looked for any sort of leak in the tank (behind the seat) but can't find anything. Could it be any sort of vent issue??

Also, I know the carb is running really rich right now and I've got to adjust it but I don't think that would cause the gas smell after the truck has been sitting overnight

Thanks for any suggestions

cdowns · 11-03-2003, 12:12 PM

wonder what year truck??

stingray72 · 11-03-2003, 12:21 PM

Oh.. sorry.. 1970 Chevy C10. Gas tank behind the seat

stingray72 · 11-03-2003, 03:09 PM

I'm gonna take the seat out tonight and really search for anything but I know someone has an idea what this could be. I've been smelling gas all over myself all day b/c of this.

shuttermutt · 11-03-2003, 03:33 PM

Probably not much help here, but every time I fill 'er up the truck and I both wreak of gas for a day or two. It's been that way with every "behind-the-seat" Chevy I've ever owned.

'Course, if your problem has only just popped up then...

stingray72 · 11-03-2003, 03:40 PM

I just bought the truck. It only had about 1/4 tank of gas when I test drove and checked everything out so it wasn't a problem that I noticed until I filled 'er up

shuttermutt · 11-03-2003, 03:44 PM

I doubt GM designed those tanks to slosh gas down the side of the truck every time the driver makes a right-hand turn and the tank is full, but every damn one I've ever had does it. Stingray brings up a good point... how the hell do you stop that? Is it just a proper cap/seal issue? You'd think I would have figured it out by now, but frankly I just never bothered.

6869704X4 · 11-03-2003, 04:05 PM

Mine was leaking around the supply line going to the fuel pump. I put some gasket sealer around it and its much better.
You also might need a vented cap. Thats the only vent for my tank. If you have one already see if its clogged.

**nightmare** · 11-03-2003, 04:07 PM

yeah, shuttermutt, it's just a proper cap/seal issue. a new cap will work.

stingray72, you might want to check the o-ring that seals the sending unit to the tank. it could be split, cracked, non-existant. anything other than soft, pliable rubber, and you'd want to replace that.

70short · 11-03-2003, 04:18 PM

Stingray72 Do you have A 72 corvette? because if you do I think that is pretty ironic. See my sig.

This happened to me the first time I completely topped off my tank with fuel. My perminent fix is going to be A blazer tank install.

stingray72 · 11-03-2003, 04:43 PM

70short. My dad and I restored his 72 Corvette and that's where the nick came from. He lets me drive it anytime I want so I call it mine also

Here's a pic if you're interested

Back on topic though.. I went and took a better look. I could've swore there was a vent hose where the filler hose was going out the side of the cab but there isn't. There is only one hose from the sending unit (my dad's 72 C10 has 3) which has to be the fuel line. The gasket for the sending unit doesn't look great but not all that bad either. I'll replace it just to be safe but it seems like there should be some sort of vent somewhere???

70short · 11-03-2003, 04:54 PM

Yes that vette looks sweeeeeeeeeeet!!!!!!!!!!!!!!!

stingray72 · 11-03-2003, 06:18 PM

Ok.. i've got some more info. I found out that my gas tank is the kind without EEC. I also drove home with my gas cap off to see if that would vent it some but it doesn't so tonight the seat comes out and I start messing with the sending unit to see if that's the problem. I can't take this, I can't breathe. If all else fails the tank goes under the bed I suppose

cdowns · 11-03-2003, 07:05 PM

check under the cab where the fuel ling goes there's a piece of rubber hose that goes to the metal fuel line that runs along the frame rail, also the gas cap can cause the fume problem as well

jjk3 · 11-03-2003, 07:57 PM

I had the exact same problem in my '68. I finally figured out that there was a pin-hole close to the bottom of the tank. That got fixed really quick when I swapped in the fuel cell under the bed. Every C-10 owner I have talked to has commented on the gas smell though. It's really a problem on most of these trucks before the Evap system. I think the best thing is to just move it to the bed, or underneath it. My .02

rustyold69 · 11-03-2003, 08:02 PM

mine always leaked gas out of the cap too, so i took some 1/4 inch rubber and made a gasket that fit just inside of my cap. The cap is kinda hard to get on but it doesn't leak all over the side of the truck either.

Longhorn Man · 11-09-2003, 01:49 AM

Another common plcae to look for a leak is where the filler neck goes into the tank. If you pay attention next time you gas up, you are proably leaning on the pump nozle as it is in your filler neck. This puts stress on the soldered tank and cracks it over the yuears.
You can remove the tank, drain it completely (or visa-versa). Then once the tank is on the floor, you'll need to remove the sending unit assembly, And then steam clean the tank out. You want to use a steam cleaner and not just a pressure washer. This will flush out all dirt and 90% of the rust too...and added bonus.
Once you can stick your nose into the tank and not smell fuel (a very minor gas smell is OK) then you can re-solder the filler neck.
The steam cleaning process can take anywhere from 1 hr to 6 hrs.
All this can be done at any compitent radiator shop for a fee.

Once you have done all this, you may as well get a kit to install a liner in the tank. POR50 makes a kick ass coating, but it takes a while to dry and your truck will be out of comission for a few days. however, you won't be getting gobs of rust in your filter and carb like you probably are now.

i posted a detailed step by step with pics on this subject...but all the nay-sayers were talking smack about me wasting my time and under the bed is the only place...blah blah blah. If you use the search...you may find it. I don't think I posted it in the FAQ, but you can look though.

**Richard** · 11-09-2003, 05:18 AM

Both my past and present 72 were leaking vapors through the fuel supply hose that connects to the sending unit. I will bet that if you look closely at the hose it has small cracks in it. Rubber tends to become less pliable over a 30 year time period. Replace all the rubber fuel lines in the cab, the ones under the hood probably would not hurt either.

stingray72 · 11-09-2003, 09:59 AM

Sorry to bring this back up but I know what (part of at least) the problem is. The gas is splattering out of the tank around the gas cap. I can see it on the paint of the bed. I sure hope that fixes the whole problem. What an easy fix... new gas cap

**Stocker** · 11-09-2003, 12:10 PM

Sure hope the new cap does the trick! FWIW, many years ago I lost my (non-locking) cap and the new one from NAPA wouldn't seal - I ended up with a locking cap from NAPA, and it's still good!

Duffy · 11-09-2003, 12:49 PM

I had the same problem with several of my trucks. I found the sending unit was the problem. Fuel was leaking from where the fuel line and vapor lines run through the sending unit flange (the round part that fills the hole in the tank). The crimp that holds the fuel lines in place had loosened up from the back of the seat bouncing into the fuel lines where they exit the tank. Every time I filled up fuel would slowly leak past the crimp and fill the cab with vapors. My solution was to remove the sending unit from the tank, hose it down real good with water and then compressed air, then I soldered the lines at the crimp. I reintalled the sending unit and no more fuel smell in the cab.

Good luck...

Duffy

11-03-2003, 11:02 AM	#1
stingray72 Red Headed Step Child Join Date: Oct 2003 Location: Atlanta, GA Posts: 1,216	Gas Tank question Ok guys.. I got a problem (and a headache). When I get in my truck in morning it smells like gas. I've looked for any sort of leak in the tank (behind the seat) but can't find anything. Could it be any sort of vent issue?? Also, I know the carb is running really rich right now and I've got to adjust it but I don't think that would cause the gas smell after the truck has been sitting overnight Thanks for any suggestions

11-03-2003, 12:12 PM	#2
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	wonder what year truck?? __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

11-03-2003, 12:21 PM	#3
stingray72 Red Headed Step Child Join Date: Oct 2003 Location: Atlanta, GA Posts: 1,216	Oh.. sorry.. 1970 Chevy C10. Gas tank behind the seat __________________ "Dinner, the perfect break between work and drunk" -Homer Simpson

11-03-2003, 03:09 PM	#4
stingray72 Red Headed Step Child Join Date: Oct 2003 Location: Atlanta, GA Posts: 1,216	I'm gonna take the seat out tonight and really search for anything but I know someone has an idea what this could be. I've been smelling gas all over myself all day b/c of this. __________________ "Dinner, the perfect break between work and drunk" -Homer Simpson

11-03-2003, 03:33 PM	#5
shuttermutt Don't say "Oops!", Doctor Join Date: Nov 2003 Location: Houston, TX Posts: 677	Probably not much help here, but every time I fill 'er up the truck and I both wreak of gas for a day or two. It's been that way with every "behind-the-seat" Chevy I've ever owned. 'Course, if your problem has only just popped up then... __________________ 'Mutt 1968 CST LWB: R.I.P. 1967 Chevelle: TPI 454 beast 1967 C10 SWB: Claimed when Bumpster didn't put it on his list

11-03-2003, 03:40 PM	#6
stingray72 Red Headed Step Child Join Date: Oct 2003 Location: Atlanta, GA Posts: 1,216	I just bought the truck. It only had about 1/4 tank of gas when I test drove and checked everything out so it wasn't a problem that I noticed until I filled 'er up __________________ "Dinner, the perfect break between work and drunk" -Homer Simpson

11-03-2003, 03:44 PM	#7
shuttermutt Don't say "Oops!", Doctor Join Date: Nov 2003 Location: Houston, TX Posts: 677	I doubt GM designed those tanks to slosh gas down the side of the truck every time the driver makes a right-hand turn and the tank is full, but every damn one I've ever had does it. Stingray brings up a good point... how the hell do you stop that? Is it just a proper cap/seal issue? You'd think I would have figured it out by now, but frankly I just never bothered. __________________ 'Mutt 1968 CST LWB: R.I.P. 1967 Chevelle: TPI 454 beast 1967 C10 SWB: Claimed when Bumpster didn't put it on his list

11-03-2003, 04:05 PM	#8
6869704X4 Registered User Join Date: Jul 2002 Location: SE NM Posts: 769	Mine was leaking around the supply line going to the fuel pump. I put some gasket sealer around it and its much better. You also might need a vented cap. Thats the only vent for my tank. If you have one already see if its clogged. __________________ The more I learn about women, the more I love my truck.

11-03-2003, 04:18 PM	#10
70short Registered User Join Date: Sep 2003 Location: Boise ID Posts: 609	Stingray72 Do you have A 72 corvette? because if you do I think that is pretty ironic. See my sig. This happened to me the first time I completely topped off my tank with fuel. My perminent fix is going to be A blazer tank install. __________________ "72" Red CORVETTE 4-speed 350 "70" Chevy Short Bed early stages of resto. Edel 600 cfm carb Weiand Stealth Intake HEI shorty Headers 4/2 Drop 295 50R 15 TOYO on 10 inch wide corvette rally rims at all 4 corners. "CHEVY RULES"

11-03-2003, 04:43 PM	#11
stingray72 Red Headed Step Child Join Date: Oct 2003 Location: Atlanta, GA Posts: 1,216	70short. My dad and I restored his 72 Corvette and that's where the nick came from. He lets me drive it anytime I want so I call it mine also Here's a pic if you're interested Back on topic though.. I went and took a better look. I could've swore there was a vent hose where the filler hose was going out the side of the cab but there isn't. There is only one hose from the sending unit (my dad's 72 C10 has 3) which has to be the fuel line. The gasket for the sending unit doesn't look great but not all that bad either. I'll replace it just to be safe but it seems like there should be some sort of vent somewhere??? __________________ "Dinner, the perfect break between work and drunk" -Homer Simpson

11-03-2003, 04:54 PM	#12
70short Registered User Join Date: Sep 2003 Location: Boise ID Posts: 609	Yes that vette looks sweeeeeeeeeeet!!!!!!!!!!!!!!! __________________ "72" Red CORVETTE 4-speed 350 "70" Chevy Short Bed early stages of resto. Edel 600 cfm carb Weiand Stealth Intake HEI shorty Headers 4/2 Drop 295 50R 15 TOYO on 10 inch wide corvette rally rims at all 4 corners. "CHEVY RULES"

11-03-2003, 06:18 PM	#13
stingray72 Red Headed Step Child Join Date: Oct 2003 Location: Atlanta, GA Posts: 1,216	Ok.. i've got some more info. I found out that my gas tank is the kind without EEC. I also drove home with my gas cap off to see if that would vent it some but it doesn't so tonight the seat comes out and I start messing with the sending unit to see if that's the problem. I can't take this, I can't breathe. If all else fails the tank goes under the bed I suppose __________________ "Dinner, the perfect break between work and drunk" -Homer Simpson

11-03-2003, 07:05 PM	#14
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	check under the cab where the fuel ling goes there's a piece of rubber hose that goes to the metal fuel line that runs along the frame rail, also the gas cap can cause the fume problem as well __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

11-03-2003, 07:57 PM	#15
jjk3 It's just a check engine lamp. Join Date: Apr 2001 Location: Melbourne, FL Posts: 311	I had the exact same problem in my '68. I finally figured out that there was a pin-hole close to the bottom of the tank. That got fixed really quick when I swapped in the fuel cell under the bed. Every C-10 owner I have talked to has commented on the gas smell though. It's really a problem on most of these trucks before the Evap system. I think the best thing is to just move it to the bed, or underneath it. My .02 __________________ Active Inliner---bigchevy66 68 SWB Stepside 250 L6/3 on the floor/ Hedman headers, HEI, MSD 6A box, K&N filter, Offy intake and Edelbrock 600cfm 4 barrel Soon to have: WC T-5 five speed 66 SWB Stepside-undergoing restoration

11-03-2003, 08:02 PM	#16
rustyold69 student wrench turner Join Date: Jan 2003 Location: wrightstown, wisconsin Posts: 192	mine always leaked gas out of the cap too, so i took some 1/4 inch rubber and made a gasket that fit just inside of my cap. The cap is kinda hard to get on but it doesn't leak all over the side of the truck either. __________________ 1969 Chevy C-10 with 250 L6 2002 GMC Sierra 2500 HD Duramax with banks six gun



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11-09-2003, 01:49 AM	#17
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Another common plcae to look for a leak is where the filler neck goes into the tank. If you pay attention next time you gas up, you are proably leaning on the pump nozle as it is in your filler neck. This puts stress on the soldered tank and cracks it over the yuears. You can remove the tank, drain it completely (or visa-versa). Then once the tank is on the floor, you'll need to remove the sending unit assembly, And then steam clean the tank out. You want to use a steam cleaner and not just a pressure washer. This will flush out all dirt and 90% of the rust too...and added bonus. Once you can stick your nose into the tank and not smell fuel (a very minor gas smell is OK) then you can re-solder the filler neck. The steam cleaning process can take anywhere from 1 hr to 6 hrs. All this can be done at any compitent radiator shop for a fee. Once you have done all this, you may as well get a kit to install a liner in the tank. POR50 makes a kick ass coating, but it takes a while to dry and your truck will be out of comission for a few days. however, you won't be getting gobs of rust in your filter and carb like you probably are now. i posted a detailed step by step with pics on this subject...but all the nay-sayers were talking smack about me wasting my time and under the bed is the only place...blah blah blah. If you use the search...you may find it. I don't think I posted it in the FAQ, but you can look though.

11-09-2003, 05:18 AM	#18
Richard Senior Member Join Date: Dec 1999 Location: Southern California Posts: 2,881	Both my past and present 72 were leaking vapors through the fuel supply hose that connects to the sending unit. I will bet that if you look closely at the hose it has small cracks in it. Rubber tends to become less pliable over a 30 year time period. Replace all the rubber fuel lines in the cab, the ones under the hood probably would not hurt either. __________________ Richard 1972 K10 Custom Deluxe SWB Fleetside My build https://67-72chevytrucks.com/vboard/...d.php?t=800746

11-09-2003, 09:59 AM	#19
stingray72 Red Headed Step Child Join Date: Oct 2003 Location: Atlanta, GA Posts: 1,216	Sorry to bring this back up but I know what (part of at least) the problem is. The gas is splattering out of the tank around the gas cap. I can see it on the paint of the bed. I sure hope that fixes the whole problem. What an easy fix... new gas cap __________________ "Dinner, the perfect break between work and drunk" -Homer Simpson

11-09-2003, 12:10 PM	#20
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,722	Sure hope the new cap does the trick! FWIW, many years ago I lost my (non-locking) cap and the new one from NAPA wouldn't seal - I ended up with a locking cap from NAPA, and it's still good! __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

11-09-2003, 12:49 PM	#21
Duffy Registered User Join Date: Jan 2001 Location: Billings, MT Posts: 121	check the sending unit too I had the same problem with several of my trucks. I found the sending unit was the problem. Fuel was leaking from where the fuel line and vapor lines run through the sending unit flange (the round part that fills the hole in the tank). The crimp that holds the fuel lines in place had loosened up from the back of the seat bouncing into the fuel lines where they exit the tank. Every time I filled up fuel would slowly leak past the crimp and fill the cab with vapors. My solution was to remove the sending unit from the tank, hose it down real good with water and then compressed air, then I soldered the lines at the crimp. I reintalled the sending unit and no more fuel smell in the cab. Good luck... Duffy __________________ '72 GMC Sierra Grande Custom Camper Last edited by Duffy; 11-09-2003 at 12:55 PM.

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