Could someone explain returnless systems?

[demonpixel]

I put an aftermarket efi system on my 72 pontiac 400 with an external fuel pump; the pump that came with the kit. i drove it today on the highway for about half an hour before i hit unexpected traffic. i slowed the car down and the car bogged and shut off. i am running one vent line from the tank to above the tank to outside air.

i'm starting to hear that returnless systems are not as reliable as return systems, but i know some ls engine cars have returnless systems. has anyone had experience with them? would running a return line make that much of a difference even if i'm properly vented? why make returnless systems at all if they're in fact unreliable? i planned on having my ls1 powered car a returnless system but now i'm not so sure.

my instruction manual says: "This system is the FIRST! of its
kind to control fuel pressure electronically and allow the
use of a single fuel line while maintaining constant fuel
pressure. This system should only be used in applications
under 500hp." OK, so is it changing the voltage of the fuel pump or something??

a buddy of mine said that my external fuel pump on my 72 firebid's system could very well be overheating; that at cruise i should be fine but sitting in traffic some of them are known to overheat. anyone else have this issue? do you recommend any external fuel pumps for daily drivers with an aftermarket efi system?

i know that's a lot of questions but it was totally embarassing pulling over on the side of the road over and over yesterday. if i let the car sit for 15-20 minutes, it started up fine and drove perfectly for about 10 minutes, and then it would just shut off. wait again, drives fine for 10 mins, then dies, wait again, etc.



thanks for any help/advice guys

[70bird]

The factory returnless systems use a return line from the pump/reg at the tank and not at the fuel rails. you still need to return un-used fuel to the tank or the pump will overheat as it dead heading against the injectors in low demand situations, but the pump is still trying to move fuel. Where is your reg. located? you should be able to run a return line from there to the tank.

[demonpixel]

thanks for the reply, 70. if that's the case why aren't all systems return style?

this systems says that the fuel pressure controls the fuel electronically. so it sounds to me like a return line is used for excess fuel (like you said) but they claim that this system has no need to compensate for excess fuel.

i messed with the car today and it idled fine for half an hour in the driveway. i revved it a little, was fine. i revved it a lot, it was fine. but check this out. my throttle linkage has a little slop in it. like when you press on the accelerator you will feel it "stop" just a little bit, before you press the accelerator down further. ok when i revved it at that stopping point, the car would want to shut down. i stuck a piece of wire in there loosely to get rid of the slop, and the car seemed fine, no problems. but the wire was set in there loosely, so when i revved the engine and it came back down to idle, the slop came back and the engine bogged again.

i've attached a pic but it's kind of a bad pic. it's hard to explain what i'm talking about if you haven't experienced it.

[Hammered]

Zig,

Some of the OEM systems return back by the tank, keeping excess fuel from being routed up over the engine. I had fuel heating problems last summer and insultated my lines and put a controller in to slow the pump down when the engine is spinning under 3k rpm.

I would guess that your controller is a pulse width modulated type. pwm controllers turn the pump on and off many times a minute and control the amount of on/off time to effectively slow it down. I can hear the SCRs in my PWM controller buzzing until it warms up.

The slop that you are noting looks like it is at the secondary throttle plates. Is that right? Maybe you've got a problem with your secondaries not closing properly and that's throwing off the IAC?

[70bird]

I'm still pretty new to EFI so I'm learning here too.

Sounds like your system includes a pump controller to compensate for low demand. Maybe it is not wired/operating properly. I belive the controller drops voltage to the pump at low RPM.
You could check voltage to the pump at different rpm/load to see if the voltage varies. If not, it isn't working properly.

I belive having a return line from the rails back to the tank is best as it prevents feeding heated fuel to the injectors.

Hopefuly one of the EFI gurus here will chime in and set us both straight.

[demonpixel]

Hey guys, talked to Retrotek yesterday. They said they send out the systems with the linkages because it helps setting idle for some people. They said that the reason why it's shutting off when i come off idle and hit the slop is because the secondaries are not opening at the same time the primaries are off idle. So John, you were close!

On my Retrotekspeed efi system, both the primaries and the secondaries need to open and close at the same time. Otherwise the engine can be starved or the opposite, flooded.

someone mentioned that a grommet would eliminate the slop. do you guys know of any other creative ways to get rid of it? i was thinking about using epoxy but that will look pretty ghetto...

[andrewb70]

If you talked to Retrotek what did they suggest? I assume that you explained your problem to them. Didn't they tell you how to fix it?

Andrew

[amx2334]

The linkage looks the same as a Holley double pumper. Can't you just bend the rod a little?
The original stalling problem sounds like something overheating.A returnless system should be more susceptible to heat soak. Is your fuel line close to any sources of heat?
You didn't notice the fuel pressure when this happened did you? I think a guage is in your future.

[demonpixel]

Yes andrew, they did. Sorry I didn't mention that. They mentioned bending the rod a little, just like amx said. seemed easier to put a grommet or something in there because i don't want to end up bending the rod too far, bending it back to get it right, and having it accidentally break lol

and no i didn't notice fuel pressure; i agree, sounds like getting a gauge is inevitable hahaha

[Hammered]

That still doesn't make sense to me. Most carbs or TBs have a progressive linkage where the secondaries don't open until the primaries are already open about 50%. Thus, a little slop between the two wouldn't matter.

I thought your problem occured when the throttle closed, not when it opened? If the secondaries are hangin open after the primaries are closed on decel, that could cause a lean out.

If on closing, you should have a spring on the secondaries that closes them independently of the primaries.

[demonpixel]

actually john i think you are right, it happens on closing. funny you mention about the spring; i do NOT have a spring on the secondaries; they are in fact hanging open after the primaries are closed at idle.

apparently i need a "secondary throttle return spring." the demon i had before this only had one return spring and that was for the primaries. does anyone have a pic of this (holley) secondary spring i need to get? i went to oreilly's last night and they had Universal springs so I was unsure what to get as I know springs come in different tensions...

thanks yet again

[andrewb70]

actually john i think you are right, it happens on closing. funny you mention about the spring; i do NOT have a spring on the secondaries; they are in fact hanging open after the primaries are closed at idle.

apparently i need a "secondary throttle return spring." the demon i had before this only had one return spring and that was for the primaries. does anyone have a pic of this (holley) secondary spring i need to get? i went to oreilly's last night and they had Universal springs so I was unsure what to get as I know springs come in different tensions...

thanks yet again

The secondary return spring is on the secondary shaft. You can see it in the picture that you posted.

Andrew

[demonpixel]

i'm going to get this and see if it helps:



Summit PN Holley 20-122. can be progressive or 1:1. i think it will help

[Hammered]

That looks cool, but I'd try bending the linkage first. It's free and hard to mess up. I would also check to see if Retrotek set you up with progressive throttle or not. Maybe their MAF requires non-progressive because it's so close to the TB and needs uniform airflow. Nonetheless, your secondaries should not be hanging open.

[t/a-speedfreak]

I'm surprised you don't send it back and ask for a replacement. That being said, I haven't heard much feedback about this system yet and would like to know if its worth the investment. I want to get rid of my carb and go EFI for reliabilty.

[demonpixel]

Hey guys, sorry it's been a while. Been on medical leave due to some torn muscles, so I haven't gotten to the car yet. I did get the 1:1 linkage from Summit, and talked to Retrotek. They DID say it was a 1:1 system and that bending the rod could help. I tried that but I think I bent it too far because the secondaries didn't go back down after hitting the throttle a little. Idle went way high.

Retrotek also claims that the systems they ship out now are sent out with an adjustable throttle linkage, that is very similar to the one I got from Summit.

Go figure.

I'll try and get this 1:1 linkage on this weekend. Everybody pray that this fixes the problem!!

[demonpixel]

ok guys, just got done installing the summit piece and ran the car for a while. while it did help some (no more "stopping point" in the gas pedal), unfortunately, my secondaries still get stuck after the rpms are 3000 or over.

i installed a pretty strong spring to help it come back down and it didn't work. the only thing that makes the secondaries come back down to idle is if i get out of the car, and push it down with my bare hand. needless to say, i am extremely pissed. i just want my car to work and i have been screwing with this thing for too long.

retrotekspeed can expect an email from me today.

[andrewb70]

Sounds like you have a defective throttle body.

Andrew

[70bird]

Are the butterflies hanging up on something? Maybe the wrong base gasket or spacer?????

[demonpixel]

good suggestion, mark. i don't think that's it though because just now i opened the throttle wide open (car is off), and the secondaries came down all the way just fine. they only get stuck when the engine is running. VOODOO

if it was the gasket it'd get stuck whether the car was on or off right?