Thoughts about using an EFI fuel pump with a carb swap

[85_SS_302_Coupe]

My buddy has an '87 that's probably going to be carbed soon and i was thinking about how to make the stock pump work right with the carb setup. People have tried and had some limited success with just regulating it down to 6-7psi, but i don't like that idea because if the regulator fails then you're in trouble.

Well, what if you ran a T fitting just before the regulator and ran another line back to the factory EFI return line? Then the gas wouldn't be under so much pressure right at the regulator and i would think it would be safe. Any thoughts on that?

[mustangboy]

I say when messing with fuel do it the right way. Does he really want to take a chance on burning his car to the ground.

[85_SS_302_Coupe]

Right, that's my thoughts on it 99% of the time...but this return line idea got me thinking about it. I would think that if a quality regulator was used then it should be just as safe as the EFI setup.

[facemelter71]

Why not just unhook the stock efi pump and hook up a low psi carbed pump (electrical) and use a pickup made for carbed cars to fit in the efi tank.I know they make them.And that would be the best way to do it.Creative performance racing has them.

[k062693w]

I'm using my factory fuel pump(efi), I just bought a regulator(carb) that has a return port for the return line to the tank.. It works great, because even if the reg fails it is still sending the fuel back to the tank.. So there is nothing really to mess up. Just my .02 anyway.

[MFIELD]

I thought I heard that it will burn the pump up fairly quickly. Plus you will be heating the fuel alot more running that much back and forth to the tank.

[k062693w]

The fuel heating I can see a little, But it has to be minimal IMO.. And as far as burning the pump out, I can't see that happening?? I could be wrong, But why would they sell regulators just for that purpose??
Like I said, I'm not sure I'm just going by wht I was told..

[YouGotJunk]

Well, what if you ran a T fitting just before the regulator and ran another line back to the factory EFI return line? Then the gas wouldn't be under so much pressure right at the regulator and i would think it would be safe. Any thoughts on that?

How could you put a T before the regulator? If there was a T before the regulator...that would mean the fuel could just free flow back through the return and FP at the regulator wouldn't build much pressure at all...if it's able to just go through the return line...I just dont see how that could work at all...It's not going to stay at 7-9lbs of FP if it can just free flow back through the return???? Does anyone else get what i'm saying???

[facemelter71]

I get what your saying JUNK.But I also get what 85 is sayin.He is thinkin like this.Lets say you have a water hose on the side of your house.When you first get it it has great pressure.Then a week later you poke a hole in it some how.You have less pressure at the head of the hose because of lost pressure due to the hole.But,it wont work on a car.Its to inconsistant.

[YouGotJunk]

I get what your saying JUNK.But I also get what 85 is sayin.He is thinkin like this.Lets say you have a water hose on the side of your house.When you first get it it has great pressure.Then a week later you poke a hole in it some how.You have less pressure at the head of the hose because of lost pressure due to the hole.But,it wont work on a car.Its to inconsistant.

Exactly! If I was going to do anything..I would just buy a good regulator...and regulate your FP to whatever you want...If and when the pump goes bad...buy a different pump that will better fit your needs!

[ibstrokin]

If you T it, you will lose volume. Volume is as important as pressure

[outlaw85]

Fuel System: You will need a new fuel pump and pickup. Do NOT use the existing EFI pump this has been done but with little success especially due to the 5/16 feed line. You can either use an electric low pressure pump designed for a carb (like the Holley red or summit brand black) or go with a mechanical fuel pump. In either case you must replace the fuel pickup on top of the gas tank with a purpose built pickup that does not include an in-tank pump. If you have a drag car it may be time to upgrade to a fuel cell or modify your existing tank for a bottom sump. At this time I also recommend you go with new fuel line from the tank to the carb. Use 3/8" minimum or larger based on your needs due to carb style fuel system needing high volume low pressure where as efi needs low volume high pressure. Remember that many sanctioned race tracks will only allow up to 12" of rubber fuel line so go with aluminum, pushlock, or braided wherever possible, and keep the lines in-between the frame rails for safety. To use a mechanical fuel pump you must change the front timing cover on the engine to one that accepts a bolt-on fuel pump. You may also need a fuel pump eccentric to drive the pump. Hope this helps this is just what I have seen in my experience.

[85_SS_302_Coupe]

OK i see what you're sayin about the T and that does make sense...i guess what you'd want is a regulator with a return line in it so it hits the regulator first and then returns to the tank what it doesn't need. Sound right?

[k062693w]

OK i see what you're sayin about the T and that does make sense...i guess what you'd want is a regulator with a return line in it so it hits the regulator first and then returns to the tank what it doesn't need. Sound right?


Yep!! That is what I said in my first post.. Unless he is planning to make a race car out of it.. But if it is just going to be a daily driver, then the regulator will be fine!! :bigthumb

[85_SS_302_Coupe]

Well you know how it is...there's always a better way to do something but sometimes you just have to work with what you've got ya know? If you can make the stock pump work safely, why not?

[facemelter71]

You can make the stock pump work.Just use some of the aeroquip ends to go from your factory fuel rail fitting's to AN fittings.There ya go.

[satan jamez]

I've known dozens of people to do this including myself on other cars without an issue.

Sometimes things can go wrong no matter what parts you put together IMO. I'd say do it :bigthumb

[IEATLT1]

85 if you decide to go with the bypass regulator let me know... I believe I have what you need.

[zlou363lx]

i have been running a stock efi intank pump for two years now on my carbed motor. it only gets about 1500 to 2000 miles a year on it though. so it hasn't been running much. i can't get the fuel pressure below 9psi with my regulator(mallory), but it works for now. i have a holley blue pump waiting to be installed, but i don't have the time or the money to change it right now.

if your friend decides to change to an out of tank pump and needs a pick-up for the top of the tank, i have one in my garage that i will not be using. i bought it from mustangboy.

[PHAT69AMX]

A By-Pass Regulator Valve is what it's called that's used this way, not a Regulator.
A regulator is for "dead head" pressure regulating.
By-Pass Regulator Valves are adjustable like a regulator or use "Pills" with diff orifice sizes
to control the flow back to the tank and the final pressure at the carb.
The return to tank line connects downstream of the bypass valve regulator.

[85_SS_302_Coupe]

Hey guys whoever has told me they have a bypass regulator for sale, let me know ASAP, my buddy is converting his over this weekend and needs it ASAP.

David,
513-377-4308

[PHAT69AMX]

There was one posted here in the Air Delivery section June 20, 2008

http://www.stangbangerz.com/forums/showthread.php?t=44386

here's the post, but their location shows as Portsmouth, Ohio

06-20-2008, 11:47 AM - IEATLT1 - Registered User Join Date: May 2006
Location: Portsmouth, OH - Posts: 142

Holley Carb Bypass Regulator
--------------------------------------------------------------------------------
Holley Carb Bypass regulator
Holley 12-803BP
used very little new 67.99
No mounting plate
box included
$25 shipped

[85_SS_302_Coupe]

Yeah i was looking for that post and couldn't find it. Anyone know how to get a hold of that guy?

[85_SS_302_Coupe]

OK guys, now i need some advice. I've got the bypass regulator hooked up with the return line and everything right, but things just aren't "right".

For starters....i have a fuel pressure gauge ran in-line right before the carb....it reads nothing except for a split second when you turn the key on. When the car is idling, it reads nothing. Do i have the wrong kind of gauge or something? It's a cheap Mr. Gasket from Autozone...

Second, it just doesn't seem like it's getting enough fuel. It idles fine and revs fine but when you drive it, it bucks like it's starving for fuel. What direction do you turn the adjustment on the regulator to add/limit fuel? It seems common sense...screwing it in should cut down fuel right?

Third, it seems to me that the fuel is just going in a circle....like it's hitting the regulator and going straight to the return line and back to the tank, and no adjustment i make on the regulator changes it. I even tried to unhook and plug the return line and adjust the regulator all the way to (what i thought was) closed, which resulted in fuel shooting up out of the vent tube like Old Faithful.


So....why doesn't the gauge work? How do i adjust the regulator? What am i doing wrong?

[satan jamez]

To increase fuel flow you need to screw the hex head in not out. Weird I know. Also me personally i've had nothing but bad luck with holley regulators. Just FYI.

Keep us posted :)

Bob

[85_SS_302_Coupe]

See i was suspicious of that....it seems to me that it's just going in a loop right around through to the return line. I'll have to play with it and see if adjusting it helps.

By the way, i LOVE these mufflers and tail pipes. Did you have them with an H or X? They sound amazing with my X pipe.
http://s229.photobucket.com/albums/ee275/EVIL85SSP/Mustang%20Pics%20and%20Videos/?action=view&current=July132008exhaustclipfun.flv

[satan jamez]

See i was suspicious of that....it seems to me that it's just going in a loop right around through to the return line. I'll have to play with it and see if adjusting it helps.

By the way, i LOVE these mufflers and tail pipes. Did you have them with an H or X? They sound amazing with my X pipe.
http://s229.photobucket.com/albums/ee275/EVIL85SSP/Mustang%20Pics%20and%20Videos/?action=view&current=July132008exhaustclipfun.flv

Your car sounds great with the long tubes and X pipe. Mine sounded like a wet fart with the H pipe and shorties :lol:

[85_SS_302_Coupe]

Well we're throwing in the towel on this one and we're gonna do it right and just convert it over to a mechanical fuel pump. I've got the regulator all the way "closed" and it doesnt' seem to want to regulate the EFI pump down below 12psi, and when you start the car the pressure slowly climbs until fuel comes out of the vent tube. We could probably run another in-line regulator after this one and that would probably do the trick but that's a bit too redneck.