Fuel only gets to engine when tank is out of the vehicle

Challis350

Junior Member
Joined
Nov 14, 2022
Posts
25
Reaction score
17
Location
Vancouver, BC
First Name
Nick
Truck Year
1986
Truck Model
C2500
Engine Size
350
Hi all. I have a 1986 GMC C2500 with a 350 & Quadrajet carb. Was running perfectly before i started work on it.

I changed the fuel tank over the weekend as the old one had become rusty and was leaking fuel. What i thought would be a one day job took three as the mounts and the tank straps were in awful condition. I re-used the original sender unit as it was working, put all the electrical connections back in place and re-used the old hoses as these seemed to be in good condition.

I go to start the truck after cycling the ignition a few times to get the fuel pump going. Truck starts....but it is not happy. A lot of hiccupping before it gets going. The engine will run, but only if I keep the accelerator pedal held down. As soon as I let off the gas the engine dies. It doesn't even try to idle.

All the initial hesitation of starting points to a fuel supply issue, but then the truck wouldn't roar with the accelerator down if it wasn't getting enough fuel?

I'm struggling to understand how me replacing a fuel tank has lead to a lack of engine idle. Any thoughts?

*EDIT: WONT START NOW*

Thanks
 
Last edited:

JamesMilk

Member
Joined
Oct 21, 2022
Posts
47
Reaction score
62
Location
Athens, Alabama
First Name
James
Truck Year
1978
Truck Model
C20
Engine Size
350
I just replaced my fuel tank, I would pony up the cash and replace the sender unit, she's probably clogged somewhere.
You could have jostled something loose that wasn't causing issues in the old tank.
 

fast 99

Full Access Member
Joined
Dec 31, 2021
Posts
661
Reaction score
676
Location
Spokane, Washington
First Name
Brian
Truck Year
81,85
Truck Model
K20
Engine Size
350
Could have picked up some crud. If air is available remove the idle screws counting the turns and put air pressure to the holes. Just a couple shots might do it. Reinstall the screws and try the idle again. Alternately use carb cleaner in those same holes.

If it is in the idle circuit might be able to tell which side is not working by dribbling fuel in each primary side on the air horn. If restricted should idle better temporarily.
 

WP29P4A

Supporting Member
Supporting Member
Joined
Jul 18, 2021
Posts
659
Reaction score
992
Location
Nevada
First Name
Mike
Truck Year
1987
Truck Model
Sierra Classic V1500
Engine Size
350 TBI
I would assume disturbing that much rust and sediment while changing the tank could send crud down stream, good time to change the fuel filter and check the screen in the carb, where the fuel line connects, if it has one.
 

Challis350

Junior Member
Joined
Nov 14, 2022
Posts
25
Reaction score
17
Location
Vancouver, BC
First Name
Nick
Truck Year
1986
Truck Model
C2500
Engine Size
350
I just replaced my fuel tank, I would pony up the cash and replace the sender unit, she's probably clogged somewhere.
You could have jostled something loose that wasn't causing issues in the old tank.
How can this be if I am able to redline the engine? Surely the engine is getting the fuel it needs?
 

Challis350

Junior Member
Joined
Nov 14, 2022
Posts
25
Reaction score
17
Location
Vancouver, BC
First Name
Nick
Truck Year
1986
Truck Model
C2500
Engine Size
350
Could have picked up some crud. If air is available remove the idle screws counting the turns and put air pressure to the holes. Just a couple shots might do it. Reinstall the screws and try the idle again. Alternately use carb cleaner in those same holes.

If it is in the idle circuit might be able to tell which side is not working by dribbling fuel in each primary side on the air horn. If restricted should idle better temporarily.
I've seen this suggested on other posts. I've stolen a bottle of compressed air from the office and will give this a go tonight!
 

Soundmound

Supporting Member
Supporting Member
Joined
Feb 15, 2022
Posts
510
Reaction score
1,056
Location
North Central Washington
First Name
Dave
Truck Year
1984
Truck Model
Scottsdale
Engine Size
305
I've seen this suggested on other posts. I've stolen a bottle of compressed air from the office and will give this a go tonight!
You didn't steal it because stealing is illegal. However, misappropriation is standard corporate practice or as progressives would state - a redistribution of CFM's has occurred to those lacking lolol.
 

75gmck25

Full Access Member
Joined
Oct 13, 2016
Posts
1,600
Reaction score
1,192
Location
Northern Virginia
First Name
Bruce
Truck Year
1975
Truck Model
K25 Camper Special TH350 NP203
Engine Size
5.7
Did you also replace or work on the fuel filters, or run the engine with the air cleaner off? Sediment/junk can get under the needle and let the engine flood, but it will usually run fine at higher rpm because it can burn the fuel and not flood out. You can get similar symptoms if you suck something into the carburetor Venturi area and block air flow.
 

Challis350

Junior Member
Joined
Nov 14, 2022
Posts
25
Reaction score
17
Location
Vancouver, BC
First Name
Nick
Truck Year
1986
Truck Model
C2500
Engine Size
350
OK so the problem appears to be getting worse. I can't start the truck now so this all points to fuel starvation. Looks like it's another cold weekend under this truck!
 

Arizona Ranger K5

Junior Member
Joined
Nov 11, 2022
Posts
4
Reaction score
14
Location
Tucson, AZ
First Name
Harper
Truck Year
1981
Truck Model
K5
Engine Size
350
Remove your gas cap, see if it idles then. New tank may have a problem with vapor lock. If that's the problem, get a 'vented' gas cap.
 

DoubleDingo

Full Access Member
Joined
Jul 3, 2012
Posts
7,760
Reaction score
7,939
Location
Right where I am
First Name
Bagoomba
Truck Year
1981, 1965
Truck Model
81-C20 Silverado Camper Special-TH400-4.10s; 65-C20 with 4:57 gears and Borg Warner Overdrive
Engine Size
Carb'ed Vortec 350; 1972 L48 350
One thing that came to mind, you said it took three days. You used the old sending unit, the fuel in the lines could have congealed in those three days, and the debris from the tank could also contribute to clogging. That, and you used the old hoses. Get a new sending unit and hoses, replace any filters there are, definitely in the carb, but also any in-line filter if there is one.
 

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
8,248
Reaction score
4,729
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
You didn't steal it because stealing is illegal. However, misappropriation is standard corporate practice or as progressives would state - a redistribution of CFM's has occurred to those lacking lolol.
I mean, you just dragged politics into this for no reason, but you actually made a progressive point right before the dig.

Plus the amount of mergers, takeovers... are increasing way too much. Too few competition. We broke up standard oil when it was way way way way way less put together as exxon mobil or disney etc


misappropriation is standard corporate practice


You must be registered for see images attach
You must be registered for see images attach

You must be registered for see images attach
You must be registered for see images attach




 

Challis350

Junior Member
Joined
Nov 14, 2022
Posts
25
Reaction score
17
Location
Vancouver, BC
First Name
Nick
Truck Year
1986
Truck Model
C2500
Engine Size
350
One thing that came to mind, you said it took three days. You used the old sending unit, the fuel in the lines could have congealed in those three days, and the debris from the tank could also contribute to clogging. That, and you used the old hoses. Get a new sending unit and hoses, replace any filters there are, definitely in the carb, but also any in-line filter if there is one.
Yup going to do all of this this weekend. Thanks for coming back and posting.
 

Forum statistics

Threads
36,989
Posts
787,227
Members
26,657
Latest member
Wannabe
Top