Gas Evaporation?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

andrew-75c10

Junior Member
Joined
Jun 20, 2020
Posts
17
Reaction score
6
Location
San Diego
First Name
Andrew
Truck Year
1975
Truck Model
C10
Engine Size
350
Is it possible that the gas from my tank is evaporating off (I assume it's not getting siphoned because I keep it behind a locked gate but maybe I could put a camera up). The gas cap is pretty old and rusty, and the fuel filler pipe is a little bent out of shape. I put a new rubber seal, but I'm not sure if the gas cap is doing its job.

Last week I parked my truck with a few gallons of gas left in the tank, and today it wouldn't start until I added another gallon from a jerry can I had on hand. The camera on my phone is busted, but I'll try to get some pictures up.
 

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
4,204
Reaction score
6,158
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
Absolutely fuel can evaporate from fuel tanks.Thats why manufacturers started putting in evaporative emission systems, to keep countless gallons of evaporated fuel out of the atmosphere.The side benefit is you get less condensation(WATER) in the tank and get to burn more of the fuel you buy. you could also have a small fuel leak in the tank( pretty common) or both.
 

80BrownK10

Full Access Member
Joined
Oct 22, 2019
Posts
1,878
Reaction score
1,240
Location
Greenwood, SC
First Name
Nate
Truck Year
1980
Truck Model
K10
Engine Size
350
Is it possible that the gas from my tank is evaporating off (I assume it's not getting siphoned because I keep it behind a locked gate but maybe I could put a camera up). The gas cap is pretty old and rusty, and the fuel filler pipe is a little bent out of shape. I put a new rubber seal, but I'm not sure if the gas cap is doing its job.

Last week I parked my truck with a few gallons of gas left in the tank, and today it wouldn't start until I added another gallon from a jerry can I had on hand. The camera on my phone is busted, but I'll try to get some pictures up.
Not this time of year unless you live in the southern hemisphere. It would take awhile for several gallons of gas to evaporate in a tank that's even open.
 

80BrownK10

Full Access Member
Joined
Oct 22, 2019
Posts
1,878
Reaction score
1,240
Location
Greenwood, SC
First Name
Nate
Truck Year
1980
Truck Model
K10
Engine Size
350
Not this time of year unless you live in the southern hemisphere. It would take awhile for several gallons of gas to evaporate in a tank that's got even a faulty cap on it.
 

Salty Crusty

Full Access Member
Joined
Apr 10, 2020
Posts
211
Reaction score
230
Location
Texas
First Name
Gary
Truck Year
1986
Truck Model
c1500
Engine Size
565
Check your gauge and/or sender
 

75gmck25

Full Access Member
Joined
Oct 13, 2016
Posts
2,049
Reaction score
1,852
Location
Northern Virginia
First Name
Bruce
Truck Year
1975
Truck Model
K25 Camper Special TH350 NP203
Engine Size
5.7
My guess would be a cracked rubber fuel line that is letting gas leak out, and is also preventing the fuel pump from drawing fuel well when the tank is low. Ethanol in the gas messes up the old rubber lines, and there are several connected to the sending unit that are hard to see.

Fill the tank at least half full, and then leave it running when parked over a clean patch of cement driveway. Look for leaking fuel while running and after shutdown.

Bruce
 

82sbshortbed

Fuckemall!!
Joined
Mar 1, 2018
Posts
14,977
Reaction score
49,720
Location
SE Texas
First Name
Doug
Truck Year
1982, 1984
Truck Model
1500 shortbed, 1500 longbed
Engine Size
454, 305
Idt a couple of gallons would evaporate in a week. But, could be wrong tho. I think it'd have to be really hot outside and cap off or something.
 

seniorbear69

Member
Joined
Oct 1, 2020
Posts
49
Reaction score
19
Location
rayleigh essex uk
First Name
steve
Truck Year
1984
Truck Model
c20
Engine Size
350
i thort he said rusty cap .maybe i read wrong ! but sad to say it stoped disapearing fule .sum scum bag helping them selves coz thay to good togo pay for thear fule same as the rest of us
 

Turbo Dog

Full Access Member
Joined
May 25, 2016
Posts
85
Reaction score
91
Location
Laramie, WYO
First Name
Dwight
Truck Year
1987
Truck Model
V30
Engine Size
388 TBI Stroker
There may not be a problem at all. You can drive in with only a couple of gallons in the tank and then not start if that isn't where the fuel pickup tube can get to it. The couple of gallons keeps moving around while you are driving allowing you to get closer to empty.

That happened to a friend lately with a different vehicle. He pulled in and parked it then couldn't get it to restart. I took a look for him and found he wasn't getting fuel. I told him he was out of fuel and he said "no way, I drove in here even though it was almost out of fuel. I was gonna fill it when I leave." Keep in mind he is an engineer and asked me not to tell anyone.
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,746
Reaction score
11,346
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
I think you have a tiny leak. If you have a plastic skid shield on your fuel tank and develop a teeny tiny leak, it can get out of the tank and then evaporate off before you see it.
 

Latest posts

Forum statistics

Threads
42,311
Posts
913,445
Members
33,809
Latest member
EazyT
Top