Both Electric And Mechanical Fuel Pump?
Thread Starter
Racer
Joined: Nov 2019
Posts: 336
Likes: 173
From: Canadian living in southern France
Both Electric And Mechanical Fuel Pump?
I have the same problem as everybody else with a '76 who is using volatile gas with alcohol added for good measure. Namely, the carb dries out if you don't drive the car for a couple of weeks.
So, I'm thinking an electric fuel pump. Turn the ignition on, wait for half a minute for it to refill the carb, start up and go.
But, why remove the mechanical pump?
The inlet valve of the mechanical pump will be opened by the pressure from the electric one, and the outlet valve will do the same thing.
I guess part of this is laziness, not having to remove the mechanical pump, re-route the fuel lines, block off the opening, etc.
But realistically, why not just leave it in place?
Any thoughts?
So, I'm thinking an electric fuel pump. Turn the ignition on, wait for half a minute for it to refill the carb, start up and go.
But, why remove the mechanical pump?
The inlet valve of the mechanical pump will be opened by the pressure from the electric one, and the outlet valve will do the same thing.
I guess part of this is laziness, not having to remove the mechanical pump, re-route the fuel lines, block off the opening, etc.
But realistically, why not just leave it in place?
Any thoughts?
Le Mans Master
Joined: Feb 2004
Posts: 7,368
Likes: 874
From: Norcal CA
2018 C1 of Year Finalist
Are you sure its not weeping out of the bowl? I know my Edelbrock does that. It has an internal leak. Another option is to install a check valve but it is easy to install an electric fuel pump. Its not really going to hurt having to take a few seconds to prime once more. It happens whenever my corvette sits in the garage for about 2 weeks without driving. It reminds me that I have to get out there more and drive. Now, I would have to say, I had have two rubber lines get ruined by the California rotten gas. Plus, I had to replace a fuel pump because the diaphragm melted by the same problem. Stabil will help with that problem.
Pro
Joined: Nov 2019
Posts: 617
Likes: 56
From: Dover, Delaware
MelWff,
Tx for the post and that's exactly what I have to do on my 78 even after Lars did his magic on my QJ..
Was always thing that an electric fuel pump may be the real answer???
Your thoughts/comments!!
JJ78
Tx for the post and that's exactly what I have to do on my 78 even after Lars did his magic on my QJ..
Was always thing that an electric fuel pump may be the real answer???
Your thoughts/comments!!
JJ78
Race Director
Joined: May 2006
Posts: 18,755
Likes: 2,589
Pro
Joined: Nov 2019
Posts: 617
Likes: 56
From: Dover, Delaware
Tx for the note MelWff,
Other possibilities is your fuel pump output check valve is weak. Going electric seems like alot of work and a potential issue compared to cranking and pushing peddle every few weeks when you drive it. Not sure if mechanical pump inlet check valve is designed for pressure.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>
Yeah you are probably right about the electric pump even if one is available for my 78..
In any case can you pls tell me how to check the pump outlet valve and where can I locate it?? Or would it better to hand that job over to my Vette guy?
JJ78
Other possibilities is your fuel pump output check valve is weak. Going electric seems like alot of work and a potential issue compared to cranking and pushing peddle every few weeks when you drive it. Not sure if mechanical pump inlet check valve is designed for pressure.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>
Yeah you are probably right about the electric pump even if one is available for my 78..
In any case can you pls tell me how to check the pump outlet valve and where can I locate it?? Or would it better to hand that job over to my Vette guy?
JJ78
Le Mans Master
Joined: Jun 2019
Posts: 7,668
Likes: 2,473
From: Indiana
Other possibilities is your fuel pump output check valve is weak. Going electric seems like alot of work and a potential issue compared to cranking and pushing peddle every few weeks when you drive it. Not sure if mechanical pump inlet check valve is designed for pressure.
Other possibilities is your fuel pump output check valve is weak
crap replacement pumps are a crap shoot..i bet there is no check in the replacement pumps.. i wonder if a check valve can be put somewhere else..(in the steel line)? or a good pump.. i have a older new mexican Airtex pump i got that when the chinesium carter craps again will try..
FYI anything past 24 hours i need to crank 5-10 seconds then squirt again.. then it runs.. SOMETIMES it runs and stalls again.. so i am betting check valve lets it drain. i call it priming the oil pump
.carb still has 2 full squirts left even after 24 hours but is not enough to run until cranking
Instructor
Joined: Jul 2021
Posts: 226
Likes: 147
From: Granbury, TX
Whichever direction you go, consider a failsafe way to shut off fuel flow in an accident. A mechanical fuel pump stops when the engine stops. Modern FI cars have features that shut off the electric pump in an accident (usually tied to a tach signal). In older race cars, an oil pressure safety switch is commonly used.
I've got an electric pump on my race car that runs in series with the mechanical pump. My electric pump has a dedicated switch and I only use it for starting. Once started and stable, I turn it off. Car starts quickly, which is a good thing as high-compression can tax a battery.
I've got an electric pump on my race car that runs in series with the mechanical pump. My electric pump has a dedicated switch and I only use it for starting. Once started and stable, I turn it off. Car starts quickly, which is a good thing as high-compression can tax a battery.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Race Director
Joined: May 2006
Posts: 18,755
Likes: 2,589
Tx for the note MelWff,
Other possibilities is your fuel pump output check valve is weak. Going electric seems like alot of work and a potential issue compared to cranking and pushing peddle every few weeks when you drive it. Not sure if mechanical pump inlet check valve is designed for pressure.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>
Yeah you are probably right about the electric pump even if one is available for my 78..
In any case can you pls tell me how to check the pump outlet valve and where can I locate it?? Or would it better to hand that job over to my Vette guy?
JJ78
Other possibilities is your fuel pump output check valve is weak. Going electric seems like alot of work and a potential issue compared to cranking and pushing peddle every few weeks when you drive it. Not sure if mechanical pump inlet check valve is designed for pressure.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>
Yeah you are probably right about the electric pump even if one is available for my 78..
In any case can you pls tell me how to check the pump outlet valve and where can I locate it?? Or would it better to hand that job over to my Vette guy?
JJ78
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Read a discussion on teamchevelle where guys are doing that just for starting only
I can see where it may help...dont wanna destroy my starter.
If its sat for a long time you can use an old dishwash soap bottle, fill with gas and fill the bowls with it.
I can see where it may help...dont wanna destroy my starter.
If its sat for a long time you can use an old dishwash soap bottle, fill with gas and fill the bowls with it.
Le Mans Master
Joined: May 2008
Posts: 9,063
Likes: 2,736
2022 C3 of the Year Finalist - Modified
If you to have to crank for 30 seconds something is broke. I have had both a quadrajet and Holley on my 77, and it never required anywhere near that time….10 second max, normally less.
Race Director
Joined: May 2006
Posts: 18,755
Likes: 2,589
Race Director
Joined: Mar 2017
Posts: 11,960
Likes: 4,516
From: Virginia
I'd rebuild the carb before adding a fuel pump. If cranking is too hard, you can pour fuel into the carb manually.
My experience has been the same as @CorvettePassion. 10 seconds of cranking, even for a car parked a few weeks or months.
Do you have a proper fuel filter, with a check valve?
My experience has been the same as @CorvettePassion. 10 seconds of cranking, even for a car parked a few weeks or months.
Do you have a proper fuel filter, with a check valve?
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,235
Likes: 9,376
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
Back in the day folks would add an electric fuel pump as a backup to the mechanical if they ended up with vapor lock. If your mechanical pump still works, run the electric pump, a type that is flow through, to prime the carb, then shut it off. I run just the electric and its pretty loud, not as loud as electric fans but you can hear it easily. Make sure you run a stand alone wiring system with its own fuse and a relay to power it. They can suck some juice and if its just added to your fuse block you may end up going through a lot of fuses....and it really sucks climbing under there to change them. For example I would add a fused line from the fuse block as a trigger wire to the relay and run a seperate 10 gauge wire from the battery to the new electric pump which has to be next to the tank as you need good head pressure to keep up with the flow demand and you dont want to collapse a rubber fuel line.
And I had a carb from Lars that still did what yours did, Either it had weeping plugs, a porous fuel bowl and it was soaking through the casting or just evaporating. I had the check valve fuel filter, a inline fuel one way check valve, plus new mechanical pumps all in at the same time....sometimes you cant fix it without spending money on a new one when the old one still performs well
And I had a carb from Lars that still did what yours did, Either it had weeping plugs, a porous fuel bowl and it was soaking through the casting or just evaporating. I had the check valve fuel filter, a inline fuel one way check valve, plus new mechanical pumps all in at the same time....sometimes you cant fix it without spending money on a new one when the old one still performs well
Last edited by Rescue Rogers; Oct 21, 2022 at 11:31 AM.
Thread Starter
Racer
Joined: Nov 2019
Posts: 336
Likes: 173
From: Canadian living in southern France
Or, what if it's sat for a while and my wife gets mad at me and I have to make a quick getaway?
Thread Starter
Racer
Joined: Nov 2019
Posts: 336
Likes: 173
From: Canadian living in southern France
Other possibilities is your fuel pump output check valve is weak. Going electric seems like alot of work and a potential issue compared to cranking and pushing peddle every few weeks when you drive it. Not sure if mechanical pump inlet check valve is designed for pressure.
Thread Starter
Racer
Joined: Nov 2019
Posts: 336
Likes: 173
From: Canadian living in southern France
Whichever direction you go, consider a failsafe way to shut off fuel flow in an accident. A mechanical fuel pump stops when the engine stops. Modern FI cars have features that shut off the electric pump in an accident (usually tied to a tach signal). In older race cars, an oil pressure safety switch is commonly used.
I've got an electric pump on my race car that runs in series with the mechanical pump. My electric pump has a dedicated switch and I only use it for starting. Once started and stable, I turn it off. Car starts quickly, which is a good thing as high-compression can tax a battery.
I've got an electric pump on my race car that runs in series with the mechanical pump. My electric pump has a dedicated switch and I only use it for starting. Once started and stable, I turn it off. Car starts quickly, which is a good thing as high-compression can tax a battery.