fuel pump question

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.

HotRodPC

Administrator
Staff member
Admin
Joined
Aug 29, 2010
Posts
47,128
Reaction score
9,299
Location
OKC, OK
First Name
HotRod
Truck Year
85 K20 LWB
Truck Model
Silverado
Engine Size
454 - Turbo 400 - 3.73
So it was necessarily a vapor return to the tank, but fuel return to the tank.
 

Snoots

Full Access Member
Joined
Jan 23, 2013
Posts
8,753
Reaction score
18,205
Location
Georgia
First Name
Roger
Truck Year
1973
Truck Model
Jimmy Sierra
Engine Size
350 w/203
I don't write it, I just present it.

I would suppose that any fuel delivered that the carb can't handle would be pumped back to the tank. That's my best guess. Why? I don't know. How did they work without it before the smog junk?

I always figured they pumped to a certain pressure and then there was a relief valve that prevented any 'backlog'? of fuel.
 

Blue Ox

Turning Diesel Fuel Into Fun
Joined
Mar 27, 2018
Posts
5,221
Reaction score
12,025
Location
LI-NY
First Name
Derek
Truck Year
MCMLXXXV
Truck Model
K20HD
Engine Size
6.2L
If the pressure gets too high the spring can't push the diaphragm until the pressure drops. So basically they just stop pumping and the lever just moves around unloaded.
 

Snoots

Full Access Member
Joined
Jan 23, 2013
Posts
8,753
Reaction score
18,205
Location
Georgia
First Name
Roger
Truck Year
1973
Truck Model
Jimmy Sierra
Engine Size
350 w/203
So you're sayin' that the spring is calibrated for a certain pressure against the diaphram and when that pressure is reached it doesn't move the diaphram anymore.
 

Blue Ox

Turning Diesel Fuel Into Fun
Joined
Mar 27, 2018
Posts
5,221
Reaction score
12,025
Location
LI-NY
First Name
Derek
Truck Year
MCMLXXXV
Truck Model
K20HD
Engine Size
6.2L
Yep.
 

HotRodPC

Administrator
Staff member
Admin
Joined
Aug 29, 2010
Posts
47,128
Reaction score
9,299
Location
OKC, OK
First Name
HotRod
Truck Year
85 K20 LWB
Truck Model
Silverado
Engine Size
454 - Turbo 400 - 3.73
Looks like I was wrong. Nice to learn tho.
I don't know what your guess was, but I was almost right but not. Hang out a bit, you'll learn lots. I get corrected on here plenty. It's the guys that WON'T BE or CAN'T BE corrected that tend to get butt hurt and run off, and so be it.
 

Snoots

Full Access Member
Joined
Jan 23, 2013
Posts
8,753
Reaction score
18,205
Location
Georgia
First Name
Roger
Truck Year
1973
Truck Model
Jimmy Sierra
Engine Size
350 w/203
Hey, I got the pic off the internet so you know it has to be true. But I trust this one.
 

Forum statistics

Threads
44,173
Posts
950,874
Members
36,290
Latest member
Pilotanpia
Top