Starving for Fuel!?!?

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.

dfaulk

Junior Member
Joined
Oct 10, 2014
Posts
8
Reaction score
1
Location
Georgia
First Name
Shad
Truck Year
1986
Truck Model
c10
Engine Size
305
Hey guys, I read post from here all the time but this is the first time posting.
I have a problem that even my mechanic can't figure out. I have a 1986 Silverado, 305 Quadrajet carb, basically all original. I can be driving down the road and the truck will die, starving for fuel. We replaced the fuel pump, tank selector (not the switch the actual valve), the connecting rod for the fuel pump and even got an electric fuel pump thinking that maybe the cam that pushes the connecting rod for the fuel pump might be so far gone that the mechanical fuel pump wasn't working. When it dies i disconnect the fuel line feeding the carb, there is no fuel flowing, but after turning the engine over a few times it starts pumping again and I'm back on the road again, for a while anyway. Any suggestion?? Thanks in advanced for anything you can offer.

SF
 

Arkansas_V8

Proud Redneck
Joined
Jul 1, 2019
Posts
3,022
Reaction score
3,961
Location
Springdale, Arkansas
First Name
Brent
Truck Year
88
Truck Model
V20 Suburban
Engine Size
5.7
Tank dirty? When it stops sucking it drops all the crud and you start over?
 

dfaulk

Junior Member
Joined
Oct 10, 2014
Posts
8
Reaction score
1
Location
Georgia
First Name
Shad
Truck Year
1986
Truck Model
c10
Engine Size
305
Fuel filter looks good, I guess it could be that.
 

Arkansas_V8

Proud Redneck
Joined
Jul 1, 2019
Posts
3,022
Reaction score
3,961
Location
Springdale, Arkansas
First Name
Brent
Truck Year
88
Truck Model
V20 Suburban
Engine Size
5.7
Just a guess, but if you have checked everything up top, that's about all that's left.

Maybe a fuel line gets heated and collapses.
 

dfaulk

Junior Member
Joined
Oct 10, 2014
Posts
8
Reaction score
1
Location
Georgia
First Name
Shad
Truck Year
1986
Truck Model
c10
Engine Size
305
it is usually when it gets hot...

I'll check that.
 

1987 GMC Jimmy

Automobile Hoarder
Joined
Jan 23, 2016
Posts
5,848
Reaction score
2,387
Location
Mississippi
First Name
Jesse
Truck Year
1987
Truck Model
V1500 Jimmy
Engine Size
350
Stupid question, but are you 100% you have spark when it’s hot? Besides a vapor lock issue, which is a hard sell for me when you’re moving down the highway, and cracked rubber fuel lines, that’s about it. Are you still running the electric pump, or are you back to mechanical? Do you have the metal line going to the carb from the pump or has that been taken out or cut? I could see a clogged pickup, but if it’s doing this consistently on both tanks regardless of the fuel level, I would hold off on dropping the tanks.
 

bucket

Super Moderator
Staff member
Super Moderator
Joined
Aug 3, 2010
Posts
28,956
Reaction score
23,468
Location
Usually not in Ohio
First Name
Andy
Truck Year
'77, '78, '79, '84, '88
Truck Model
K5 thru K30
Engine Size
350-454
I've been dealing with a similar issue recently, although mine is more related to how much I'm into the go pedal and how long. If I lay into the throttle, the truck goes like hell, but when it nears time to shift, it runs out of fuel and I have to let off the throttle so the pump can catch back up. Towing a heavy load aggravates the issue. The tank is clean, the lines are clear, filter is clear and the mechanical pump maintains pressure. The next step is the carb. My hunch is the float is sticking and not fully opening the needle/seat.
 

dfaulk

Junior Member
Joined
Oct 10, 2014
Posts
8
Reaction score
1
Location
Georgia
First Name
Shad
Truck Year
1986
Truck Model
c10
Engine Size
305
Stupid question, but are you 100% you have spark when it’s hot? Besides a vapor lock issue, which is a hard sell for me when you’re moving down the highway, and cracked rubber fuel lines, that’s about it. Are you still running the electric pump, or are you back to mechanical? Do you have the metal line going to the carb from the pump or has that been taken out or cut? I could see a clogged pickup, but if it’s doing this consistently on both tanks regardless of the fuel level, I would hold off on dropping the tanks.


I switched back to the mechanical pump and I am still using the original metal line to the carb. My mechanic put a new distributor on the truck as well. He said the same thing about it just going dead moving down the highway. It happened yesterday on the way back from work, disconnected the supply line re primed and then it cranked right up. I have driven it a week with out incident them boom. Someone suggested the sock in the tank might be clogged up.


I've been dealing with a similar issue recently, although mine is more related to how much I'm into the go pedal and how long. If I lay into the throttle, the truck goes like hell, but when it nears time to shift, it runs out of fuel and I have to let off the throttle so the pump can catch back up. Towing a heavy load aggravates the issue. The tank is clean, the lines are clear, filter is clear and the mechanical pump maintains pressure. The next step is the carb. My hunch is the float is sticking and not fully opening the needle/seat.

Yep, same here, i forgot to mention this in the original quote. Had another buddy suggested the float, but when there is no fuel going to the carb, in my case, its hard for me to believe it is the carb.

That LS swap is looking better and better....
 

MisterB

Full Access Member
Joined
Sep 9, 2019
Posts
676
Reaction score
845
Location
Northwest
First Name
AJ
Truck Year
1980
Truck Model
GMC K2500 4X4
Engine Size
350
Might be a carb issue too.

Sent from my SM-N975U1 using Tapatalk
 

gotyourgoat

Full Access Member
Joined
Mar 27, 2014
Posts
2,117
Reaction score
3,417
Location
NRV Virginia
First Name
gotyourgoat
Truck Year
1984
Truck Model
c10
Engine Size
smokin' 305
That LS swap is looking better and better....

Sadly it would only be solving the problem because you would be replacing the entire fuel system.

You mentioned fuel isn't flowing when you take the line off but when you crank it fuel comes out. That's normal, it's not a pressurized system like fuel injection.

Are you running an aftermarket filter? Have you checked the filter in the carb?
 

omillan99

Full Access Member
Joined
Jan 22, 2015
Posts
85
Reaction score
25
Location
El Paso, TX
First Name
Oscar
Truck Year
1978
Truck Model
K20 Scottsdale
Engine Size
350 4 Bolt
Sadly it would only be solving the problem because you would be replacing the entire fuel system.

You mentioned fuel isn't flowing when you take the line off but when you crank it fuel comes out. That's normal, it's not a pressurized system like fuel injection.

Are you running an aftermarket filter? Have you checked the filter in the carb?

If you run one of those cheap clear filters before the carb you'll quickly be able to tell if fuel had been flowing. I would start with that and force it to stall in a safe area so you can check that. It'll at least give you an idea if its from the before or after the pump.
 

Snoots

Full Access Member
Joined
Jan 23, 2013
Posts
8,158
Reaction score
15,957
Location
Georgia
First Name
Roger
Truck Year
1973
Truck Model
Jimmy Sierra
Engine Size
350
Recently had a similar issue. Turned out to be the sock on the fuel pickup. It was coated with crud.
 

gotyourgoat

Full Access Member
Joined
Mar 27, 2014
Posts
2,117
Reaction score
3,417
Location
NRV Virginia
First Name
gotyourgoat
Truck Year
1984
Truck Model
c10
Engine Size
smokin' 305
If you run one of those cheap clear filters before the carb you'll quickly be able to tell if fuel had been flowing. I would start with that and force it to stall in a safe area so you can check that. It'll at least give you an idea if its from the before or after the pump.
I can't condone that type of filter. Replaced my line from the pump to carb and got rid of over a half dozen connections. The clear plastic filter could also be seen visibly pulsing from the pump at idle. God knows what it was doing when I was playing with the loud petal. I consider my rig much less of a fire hazard without one.
 

semperfiguy98

Full Access Member
Joined
Apr 28, 2016
Posts
57
Reaction score
106
Location
Camas, WA
First Name
Michael
Truck Year
1986
Truck Model
Suburban K20
Engine Size
350
Try running with the gas cap loosened a turn or so. Could be vacuum in the fuel tank as you're driving and using fuel. That fuel should be displaced by air, but if there's a blockage, then when you use enough fuel then a partial vacuum is created in the air space inside the tank, which won't allow fuel flow until the pressure equalizes. If it runs fine after loosening the cap, then you just have to find where it's blocking the vent. Good luck.
 

omillan99

Full Access Member
Joined
Jan 22, 2015
Posts
85
Reaction score
25
Location
El Paso, TX
First Name
Oscar
Truck Year
1978
Truck Model
K20 Scottsdale
Engine Size
350 4 Bolt
I can't condone that type of filter. Replaced my line from the pump to carb and got rid of over a half dozen connections. The clear plastic filter could also be seen visibly pulsing from the pump at idle. God knows what it was doing when I was playing with the loud petal. I consider my rig much less of a fire hazard without one.

I run those and I've had no issue, but i was thinking just to diagnose the issue. It would be easy to go back to not having that filter.
 

Latest posts

Forum statistics

Threads
41,853
Posts
903,552
Members
33,366
Latest member
texdave
Top