1968 plumbing a feed/return line for EFI

[tomcwarren]

I'm getting ready to tinker again (now that the temps are down below 100 here), and I'm looking at changing from carb to TBI EFI. Lots of good info @ DIYAutoTune, etc. on using GM eek 2-port TBI parts from Pick-a-Part, or a used Holley TBI from Ebay. Throttle Body Injection (TBI) sits on top of the manifold, just like a carb, so no major engine mods needed.

I ordered an O2 sensor on Ebay (Innovate LC1 + gauge) so I can get a baseline AFR at idle/cruise/WOT with the carb, and later run closed loop with the EFI ECU (progably a Megasquirt unit). That install should be easy - just need a bung welded into the header.

Part of an EFI conversion is a high-pressure (HP) fuel pump to the TBI's regulator (injectors need 10-20 PSI), and any unused fuel has to return to the tank via a low-pressure (LP) return line (4-6 PSI, I think).

My question (finally!) is - has anyone had any experience with adding a HP fuel pump, regulator and LP return line on a '67/68? I'm interested in how / where the pump was mounted, pre- and post- filter placement, and return line routing. Also any thoughts/info on using braided HP line vs. the newer composite/plastic HP fuel line from Spectre, Summit, Earls, etc.

One option is to keep the present stock hardline for use as the return line (via a fitting tapped into the stock fuel sending unit to dump fuel back into the tank), and route a new HP line down the pass side, with the HP pump mounted near/below the tank.

Another thought is that the stock hardline is there, ready to use as the feed into the HP pump (which can't suck gas, but can push it @ high pressure), so I could use the complete stock assembly including the mech fuel pump to feed the HP pump (somehere in the engine bay), into the TBI regulator, and just run a low-pressure return line back down the pass side to the tank, dumping into the modified fuel sender, or into the filler neck, or even into the tank drain plug.

So let me know if you've done this, seen it done, or have any ideas on how it _should_ be done. I want it to be clean AND safe, but also easy to return to stock if I decide to sell or am unhappy w/EFI.

Thanks,

Tom

 

[robert campbell]

Tom,
Check these guys out!

http://www.retrotekspeed.com/product.php?pk=52

They have high pressure "returnless" fuel pump systems. May make your job alot easier. One of my next major buys may be one of their complete systems on top of my blower. Self learning and the bomb.

Fuel and bomb together.... whooppss.... Great articles in Hot Rod about them.

Rob

 

[tomcwarren]

Thanks, Rob. I'd seen a returnless system from them before, but it was standalone (w/it's own PWM controller). The only thing they have now is this:

http://www.retrotekspeed.com/products/fuel-system-components/returnless-fuel-system-kit.html

At $300, that's too high, and it appears to only work w/their ECM.

I do like the idea of returnless via a PWM pump module, since it only runs the pump full-on during high-demand times (WOT, accel), and keeps it at some lesser percentage at idle and cruise. This has the advantage of a quieter pump and less fuel heating (since it isn't being recirculated w/a return line), but the return-line style seems simpler (technology-wise) and more cost-effective right now.

If I find a home-brew PWM EFI returnless system that works w/Megasquirt I might consider it as an upgrade later.

Tom

 

[nfrntau]

I've considered budget EFI also, please keep us updated on how this works out for you.

 

[tomcwarren]

Anyone know what the thread is on the fuel tank drain plug? Easiest option is to run my return line into the drain hole. Second-easiest is probably running it into the gas tank filler pipe mid-pipe via a welded 3/8" hose barb, but I'm no welder and don't know/trust one.

Third option is to shell out $99 for a Ron Morris modified fuel sender w/return barb (or do it myself, and again I've no welding ability).

Come on, folks. Weigh in here!

Tom

 

[franklinair]

I'm checking with my source in FL. He just installed an EFI system

Neil

 

[CougarCJ]

I have a friend that brazed or silver soldered a nipple on the fuel sender too. As I recall he routed the return line down the passenger side of the car. Mirroring the line on the drivers side. He may have used this new line for his pressure line, I don't recall.

My friend used the Holley projection injection? does that sound right? He started with a roller crate 5.0 engine and Lentech AOD transmission. Wanted to retain the basic stock look under the hood, i.e. 1968 air cleaner.

The car has been sold to a new owner, I can contact him. He has most if not all of the particulars on this build.

 

[tomcwarren]

Neil/Scott,

Any info (pics, writeups, etc.) from other builds is greatly appreciated.

Thanks!

 

[franklinair]

Can't offer much help here, as EFI is not my area of expertise. As far as the low pressure fuel return line there seems to be 3 options:
1.) Attach a fitting on the tank sending unit, requiring brazing.
2.) Attach a fitting on the fuel filler neck, again requiing brazing.
3.) Remove the fuel tank drain plug and install a threaded fitting with a fuel hose fitting. This would seem to me to be the most practical.
Hope some of this helps.

Neil

 

[CougarCJ]

Tom, I contacted the new owner of the car I mentioned, but he doesn't have anything in written form for the car.

Scott,

He did not document it, but what he did was to add a second fuel line that ran on the opposite side of the car. It was bent up from stainless, and is a mirror image of the factory line. The electric fuel pump is mounted under the car as well. It would have been better to mount it closer to the tank, but he wanted it lower than the tank to insure that it would self prime. He also had a second pipe added to the fuel sending unit for the return line. This part had to be made twice to get it right.

It is a very clean installation. Art spared no expense to get it done the way he wanted it.

Bill B

That is all that Bill could add.

Tom, Bill B lives in Fountain Hills, Az. I could probably put you in direct contact with him.

 

[tomcwarren]

Thanks, Neil. Those are the 3 options I listed earilier. Looking for info on the size (NPT) of the tank filler plug so I can buy a 3/8"-to-X NPT adapter. The other two options (filler neck and return in sending unit) are still viable - just hoping someone had done this before/had pics, etc. and could provide specifics.

Scott - great info - probably the way I'll go (although I might return via the drain plug for phase-one, then see about a sending-unit-mod later). I'm still gathering info/parts/etc. for now, whilst watching some Ebay TBI auctions for various GM and Holley TBI parts/systems.

Tom

 

[p51]

Re: Another thought is that the stock hardline is there, ready to use as the feed into the HP pump (which can't suck gas, but can push it @ high pressure), so I could use the complete stock assembly including the mech fuel pump to feed the HP pump (somehere in the engine bay), into the TBI regulator, and just run a low-pressure return line back down the pass side to the tank, dumping into the modified fuel sender, or into the filler neck, or even into the tank drain plug.

Hey Tom

Reopening this thread... as I'm considering adding EFI in my quest to "make it look 1968 but drive 2008". I'm looking at the Powerjection III with the returnless PWM "Fuel on Demand" controller which requires no return line. Here shown being installed in a Mach1...

http://www.youtube.com/watch?v=jJlntQ5txZQ

So, I was intrigued by your idea of putting the EFI pump in-line but *after* the stock pump which not only keeps the car easily convert-able back to stock but allows one to keep the low pressure fuel line from the tank all the way to the engine compartment. This *seems* like an excellent (!!) idea.

Did you do this?

Any downside issues that anyone can think of?

The guys @Retrotek put the pump near the tank. Is there something that requires it in the back near the tank (safer? maybe having all the fuel which is in the line from the tank as a sort of "high pressure reservoir" means less lag on acceleration? ????)

Another benefit in having the pump in the engine compartment is that any noise from the pump is clear masked by engine noise.

Like I said, seems like an excellent idea...

Thanks
James

 

[nfrntau]

The reason to install fuel pump near the tank down low is to keep it primed at all times. The pump needs to be below the tank.
I also agree with you that it would be quiter back there as well.

 

[p51]

The reason to install fuel pump near the tank down low is to keep it primed at all times. The pump needs to be below the tank.
I also agree with you that it would be quiter back there as well.

Thanks. Thats also what I've found from a bit of research last night. It appears that if you put the efi pump in the engine bay (or somewhere away from the tank) you need two things: (1) a low pressure pump to feed (2) a small "surge tank" that, in turn, feeds the high-pressure efi pump. The surge tank provides continuous flow so that the efi pump doesn't suck air or cavitate.

So, if you use the existing low-pressure mechanical pump (for the carb) to feed a surge tank (again, up front in the engine bay) you'd get something like this...

http://sdsefi.com/techsurge.htm

With a returnless system (PWM controller for the efi pump) you should be able to remove the return lines (in the above diagram) to the surge tank and from the surge tank to the gas tank. This overall *seems* to minimize the changes to the fuel system of an existing carb setup.

Regarding noise, I was sort of thinking the engine noise in the front might mask any pump noise...

 

[nfrntau]

At 100 mph I imagine that pump will be screaming

 

[tomcwarren]

Sorry, guys. Didn't see this til now.

I went with a Holley EFI (TBI) system, but never did get it to idle well (used the cheapest Holley controller, with knobs instead of a computer interface to control idle, cruise, power, etc. settings in the fuel map - not a great way to go). I've since removed it (it's for sale if anyone wants it!), but left the electric Holley pump and return line in place to cure a vapor-lock problem in the summer heat w/my Edelbrock carb.

I looked at the PowerJection systems, but couldn't find a recent one that still had the PWM returnless option. That '69 Stang youtube video is pretty old now. I just went with a stainless 3/16" return line down the passenger side, back in thru the drain plug. The Holley pump sits on a bracket just in front of the tank (pretty well protected from road debris). It's fed from the stock tank feed, thru a standard fuel filter, and pushes thru the stock (5/16"?) fuel line down the driver's side rail and into the carb. I left my old mech pump attached in case I want to return to original config.

Note that electic pumps are pusher pumps, and the Ford mech pump is a puller pump. So you either need to gravity feed the elect pump (keeping it near the tank), or push fuel to it (or to a tank, as you discovered) with a mech pump. I went with the gravity feed/pusher config, as that's what Holley had in there EFI manual.

I ran the input fuel line thru a Mallory regulator, which allows me to get the 5-6 PSI I need for my carb, and it spews the rest of the fuel back down the fenderwell, back to the tank thru the return line. Works great, and I included a switch just to the right of the fog light switch so I can kill the fuel pump if I need to (theft deterrent, emergencies, etc.). I should probably add an inertia switch from a Taurus, etc. in the trunk to protect against fuel spew in the case of a rear-end collision, but I haven't got around to that yet.

Running the return line was a day's work - get a good tubing bender, plan ahead, and secure the line every foot or so w/clamps. I haven't noticed the pump making a ton of noise, but my headers & exhaust are a bit loud, so I probably wouldn't notice it when I'm driving.

Good luck, and let me know if you find a returnless system that works well.

Tom

 

[p51]

Tom

Thanks for the info. I'm still in the "thinkin' 'bout it" stage - half the fun is the planning :smile:

I'll let you guys know if I go ahead with it and how it turns out, etc

James