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Fuel Delivery - EFI Conversion?


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Currently I'm running the good ol' Mr. Gasket 12v electric fuel pump.  I adopted this car in the middle of its conversion, and interestingly the guy I got it from had the fuel pump mounted in the engine bay, rather than the usual 1 foot or so from the fuel tank.  But it works, kinda.

 

Post-pump fuel pressure is about 4.5 PSI.  As I understand it that's a bit low for a 4-barrel Edelbrock Carb - I need about 5-7 PSI.  That could be why I'm having some fuel starvation issues when I gun it hard.  I'm considering completely re-doing my fuel delivery system.  Curious if anyone has played with an EFI conversion kit such as this.  Figured if I'm gonna run new lines and everything it might be worth a try.

 

For reference my engine is a 350 out of a 1970 Bel Air.

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I imagine the volume is a problem with the Mr. Gasket pump (I had one as well, but feeding the a stock L28), at almost double the displacement I imagine you are running out of volume to maintain the pressure.

 

The pumps are designed to push more than pull, so having it near the engine bay is causing it to do more work pulling the fuel rather than pushing it. Granted the way the pick up and all that is in the stock tank as I remember the pumps will always be pulling anyways.

 

If the carb setup works than replacing it with a higher volume slightly higher pump with an adjustable regulator should work fine, so I'm not sure if it is a good reason to upgrade, but upgrading it would "solve" the problem.

 

I would say if you are more tired of dealing with the carbs, needles, valves, jets, etc or looking for a bit more fuel efficiency would be a better justification.

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3 hours ago, Revenant said:

.  That could be why I'm having some fuel starvation issues when I gun it hard.

 

How do you know it's fuel starvation?  What does "gun it hard" mean?

 

Like SJ says, you really just need the volume to keep the float bowls full.  You can measure the rate to see what you're getting. 

 

An EFI conversion isn't going to be easier than getting a carb to work.

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4 hours ago, NewZed said:

How do you know it's fuel starvation?  What does "gun it hard" mean?

 

Just for an example:  Say I'm cruising along at 30mph, downshift, then rapidly accelerate to 50, wide open throttle.  When I hit about 45mph, the engine will start to bog down, similar to the symptoms of vapor lock (It's not overheating though.)  

 

I'm sure an EFI would be more expensive and complex than just relocating/replacing the fuel pump and dialing in the pressure, but it seemed like it'd be an interesting project and I was curious if anyone had tried it.

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I think as a super rough estimate, it is roughly 10hp/gallon. The mr gasket pump pushes what it says is 28gph. My last friend with a 350 said his motor pout out at least 300hp so I could see you using more fuel then the pump can supply especially if it is pulling instead of pushing.That is with good quality wire as well, if it is thin gauge I can see the pump pushing substantially less.

 

I had a similar issue with my L28, made me end up hating the motor and I went one step further in looking to do an engine swap. Similarly in a way it would suddenly cut power if you got on it HARD for a long duration. When I went to execute my swap I found that the fuel pump wire from the relay was loose. So under hard acceleration it would come off so the car ran until the fuel bowls went dry then would run real rough then as the g's returned to neutral the wire would move and come into arcing distance and fill the fuel bowl. 

 

The newer EFI conversions are pretty neat, some have pretty decent auto tuning setups and some like this one apparently has PWM to control the fuel pump to maintain fuel pressure and I assume run just a feed line, but I just don't want you to drop a nuke to kill a mosquito. Might be a higher volume pump and a pump placement change would remove the hesitation for quite a bit less in time and effort.

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The same pump couldn’t keep up with my modified L28.  A $50 carter pump had no issues.  Im now fuel injected and it’s come with a whole bother can of worms.  In fact enough that I’ve barely driven the car over two summers (while not putting in a huge amount of effort).

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I don’t know the name but it was a high flow pump off of some 454 based vehicle. Super loud but did the job. When I went EFI, I tossed the surge tank idea out when I was running out of space in the back. My Walbro whispers in comparison to that Carter.  Haven’t had any starvation issues using the drain out the bottom of the tank. I also haven’t been to an autox since the conversion. 

Edited by HuD 91gt
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On 6/14/2018 at 2:36 PM, Revenant said:

Currently I'm running the good ol' Mr. Gasket 12v electric fuel pump. 

 

https://www.summitracing.com/search?SortBy=bestkeywordmatch&SortOrder=ascending&keyword=mr%20gasket%20electric%20fuel%20pump&cm_mmc=ppc-google-_-search-_-all-part-types-_-keyword

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  • 2 weeks later...

Just an update:  Been playing with wiring configurations, filter locations and such with the Mr. Gasket 12v pump.  At one point, running straight 12v from the battery to the pump with a good ground, I was getting 6.5psi, which is ideal for my particular carburetor (Edelbrock 1406 Performer.)  Can't figure out what I did to get that.  Later I was getting nil pressure until I manually primed the fuel line (read: sucked on it till I spit out gas, pinched it off, then plugged it into the pump inlet) at which point I got about 4.75.

 

I'm going to try to relocate the pump closer to the gas tank.  Problem now is the stock fuel-pump hot lead that branches off of the float sensor bundle is cold, so I'm gonna have to run a wire from a switched 12v source up front.  

 

Will continue to update in case it helps anyone else in my situation.  Also, any pics of electric fuel pumps mounted near the fuel tank would be helpful.  I've scouted a few decent mounting spots but have yet to check for a solid ground as of yet.

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Quick update:  I found a new Mr. Gasket electric fuel pump lying around that I hadn't even taken out of the box.  Mounted that near the fuel tank so I have no more than about 1 foot of line to the inlet.  Also found out that the guy who I bought my Z from was for some reason running fuel from the return line, rather than the actual outlet on the tank...so I fixed that.  

 

Ran power to it, pressurized, no leaks.  Adjusted the mixture after warming it up, and took it for a drive.  No more starvation!  Pulls smooth and hard!  Thanks all for the suggestions!  Getting about 6psi at the carb so I'm not gonna mess with a regulator until I do some more tuning.

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