Mechanical fuel pump tank return bypass?

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.

nabeshin

nabeshin

functioning lunatic
Joined
Jan 23, 2020
Posts
464
Reaction score
857
Location
Cozad, Nebraska
First Name
Grae
Truck Year
1976
Truck Model
K10
Engine Size
400
Tried to do a bit of search here but didn't come up with much.

I noticed my fuel pump is leaking; squirts of fuel out the back end of the flying saucer part at the seam towards the manifold. I was checking to see if I had fixed an exhaust leak after tightening the manifold down pipe nuts when I saw this.

Exhaust is fine now, but I need a new pump. It was replaced at some point, it is not original, but seems to be an AC Delco unit. It has two outputs, one to carb, and one to return to tank. Summit is a little light on replacements with a return, can i cap the return and just use a pump with one outlet to the carb?
 
nabeshin

nabeshin

functioning lunatic
Joined
Jan 23, 2020
Posts
464
Reaction score
857
Location
Cozad, Nebraska
First Name
Grae
Truck Year
1976
Truck Model
K10
Engine Size
400
Summit is my go-to, didn't really think to check Amazon for car parts. Thanks.
 
Snoots

Snoots

Full Access Member
Joined
Jan 23, 2013
Posts
8,186
Reaction score
16,028
Location
Georgia
First Name
Roger
Truck Year
1973
Truck Model
Jimmy Sierra
Engine Size
350
nabeshin said:
Tried to do a bit of search here but didn't come up with much.

I noticed my fuel pump is leaking; squirts of fuel out the back end of the flying saucer part at the seam towards the manifold. I was checking to see if I had fixed an exhaust leak after tightening the manifold down pipe nuts when I saw this.

Exhaust is fine now, but I need a new pump. It was replaced at some point, it is not original, but seems to be an AC Delco unit. It has two outputs, one to carb, and one to return to tank. Summit is a little light on replacements with a return, can i cap the return and just use a pump with one outlet to the carb?
Click to expand...

No. You should not cap the return line.
 
nabeshin

nabeshin

functioning lunatic
Joined
Jan 23, 2020
Posts
464
Reaction score
857
Location
Cozad, Nebraska
First Name
Grae
Truck Year
1976
Truck Model
K10
Engine Size
400
Thanks for the input. I'll look around on Amazon and just hope I don't get a counterfeit one.
 
gotyourgoat

gotyourgoat

Full Access Member
Joined
Mar 27, 2014
Posts
2,117
Reaction score
3,418
Location
NRV Virginia
First Name
gotyourgoat
Truck Year
1984
Truck Model
c10
Engine Size
smokin' 305
You are not seeking the unobtainable. Any parts store will sell you a mechanical fuel pump for a small block Chevy. And if summit is out, there's always rockauto or jcwhitney or jegs or Ebay or a thousand other places.

Or there's one in the bed of my truck I bent up with a cheater bar trying to force a damaged flair fitting to seal. You can have that one for free.;)
 
1987 GMC Jimmy

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
Snoots said:
No. You should not cap the return line.
Click to expand...

I couldn't agree more. My car was made literally weeks before they started putting return lines on them, and it will not fail to vapor lock after a hot soak with ambient temps of >80*F. If I knew what I know now back then, I would have gone with the three line sender, ran a braided line, and gone with a return style pump. I don’t know how much it helps, but it’s better than nothing.
 
S

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,742
Reaction score
11,318
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
Get a pump with a return line. The main purpose to that line is to keep the fuel in the line before the pump moving, this reduced vapor locking. Trust me it really does make a difference.
 
75gmck25

75gmck25

Full Access Member
Joined
Oct 13, 2016
Posts
2,038
Reaction score
1,833
Location
Northern Virginia
First Name
Bruce
Truck Year
1975
Truck Model
K25 Camper Special TH350 NP203
Engine Size
5.7
I bought a new 3 fitting fuel pump for my truck last year and was able to find it in stock at Autozone. Its not a Delco, but for a part that cheap and easy to replace I'm not concerned with using a store brand part.

Bruce
 
Donald

Donald

Full Access Member
Joined
Jun 24, 2018
Posts
74
Reaction score
167
Location
Loris SC.
First Name
Don
Truck Year
1985
Truck Model
GMC 1500
Engine Size
350 / 290
I installed a blazer tank on my c15 and capped the return line at the pump a year ago and it works great .
 
Matt69olds

Matt69olds

Full Access Member
Joined
Jan 8, 2018
Posts
2,352
Reaction score
3,598
Location
Central Indiana
First Name
Matt
Truck Year
81
Truck Model
GMC 1/2 ton
Engine Size
455 Olds
The other advantage of the return line is to drop fuel pressure at the carb once the engine shuts down. After a hot soak, fuel trapped in the fuel line between the pump and the carb can begin to boil, raising the fuel pressure high enough to push fuel past the needle and seat and flooding the engine. The return line fitting in the pump has a small orifice that bleeds off fuel back to the tank. As stated before, the constant fuel circulating help kept the pump and fuel coil.
 
You must log in or register to reply here.

Similar threads

Powerhouse Ranch
460 BBC Mechanical Fuel Pump
Replies
6
Views
846
bucket
bucket
rcotner
Dual fuel tank to single fuel tank pigtail wiring connection
Replies
2
Views
1K
rcotner
rcotner
7
Fuel line
Replies
3
Views
270
SquareRoot
SquareRoot
K
Best Fuel Tank Selector Valve Brand?
Replies
1
Views
793
AuroraGirl
AuroraGirl
I
1987 Silverado 454 TBI to carb fuel return line, can I cap it off?
Replies
3
Views
613
Ricko1966
R

Latest posts

Forum statistics

Threads
42,125
Posts
909,619
Members
33,617
Latest member
dougli1
Top