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:

https://static1.pt-content.com/images/pt/2008/03/hly20122_w-1.jpg

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 :confused:

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

[70bird]

Voodoo indeed! If it was an interference problem, it seems to me it wouldn't matter if the motor is running or not. Is there a stepper motor of some kind on the pass. side? Probably not. How about the TPS possibly hanging up?

Maybe try this, shut the motor off when this happens and see if the secondaries close by themselves. If not you can rule out a vacuum related issue, and get back to looking for a mech. interference. Maybe you could disconnect the new linkage, start the motor and rev it while opening the secondaries manualy to see if the same problem occurs. If the problem persists, you can rule out a problem with the linkage. At the same time you could check (with the motor off) the movement of the secondaries independently to feel for any sticking points.

You stated that when this happens you have to close the secondaries by hand. Do you mean that you are pushing on the secondary shaft to do this? Or can you just push on the primary shaft to do the same thing?

As Andrew said, sounds like you have a defective throttle body.
Hopefuly you can exchange it!
Good luck

[demonpixel]

yes, i'm pushing on the secondary shaft to close them. i can't just push on the primary shaft to do the same thing.

right now i'm going to disconnect the new linkage and when the car is at running temp, i'm going to open the secondaries and see if they stick. if they're still open, i think you might be on to something relating to vacuum keeping them open...

i'll post yet another update in a few minutes. thanks mark!

[demonpixel]

well, sure enough, when the engine is on with the new linkage off and the secondaries stuck open, when i turn off the car, the secondaries come right back down!!

i'll double check my vacuum connections, but i didn't have this issue when i first installed the system a few months ago, so i'm pretty sure i connected my vacuum correctly. maybe something is loose??

here's a screenshot of the software's vacuum gauge when it's at idle. when the rpms are 1600-2200, the vacuum gauge says -20. then the secondaries slowwwly come back down to normal.

[andrewb70]

Vacuum is not keeping them open. It's a butterfly, not a flapper. There is equal suction on either side of the butterfly. Your barking up the wrong tree.

Disconnect the link between the primaries and secondaries. Then with your hand feel the action of both the primary and secondary shafts. Do they move smoothly? Do they stick, or bind in any way? Both of the throttle shafts should have very smooth motion and should take very little force to rotate by hand.

Andrew

[amx2334]

Can you post a good picture of the linkage? It sounds like the secondary return spring isn't hooked up.

[demonpixel]

amx, here is a pic of the old linkage.

andrew, i took the linkage out and did as you suggested. they BOTH move freely and do not bind up.

now here's something my buddy did just a little bit ago. From the MAP sensor, there is a vacuum hose that goes into a T. from the T, one vac line goes to the throttle body, and the other line goes to the (automatic) transmission (as the manual says to do). (i'm running no vac advance on my distributor.) now what my buddy did was he disconnected the vac line going to the transmission and put his thumb over the hole. engine on, secondaries stuck. then he made a vacuum leak with his thumb, only covering HALF OF THE VACUUM HOSE HOLE. THE SECONDARIES CAME BACK DOWN NORMALLY. we did this over and over, no matter what the linkage was (old or new).

andrew, i know you said it's probably not vacuum, but this definitely makes me think that it's vacuum related. my bud thinks that the MAP sensor might be bad.

you guys are great for helping me out; can't believe you've helped me along this much. i can't thank you guys enough.

if anyone's interested, here's the manual: http://www.demonpixel.com/AUTOMOTIVE/Retrotek_installation_manual.pdf

another friend of mine suggested that i may have a leak in my intake manifold. since the manifold is the stock one and it's cast iron, there may possibly be a crack in it if it's from 1972. what do you guys think of this as a possibility?

[Hammered]

Maybe the spring on your secondaries is too weak to hold them shut under high vacuum?

[andrewb70]

I certainly been wrong before, it just seems odd. Keep us updated.

I still don't understand why the vendor is not more supportive. Did they not bolt these things to an engine before they started selling them? If this is a known issue, you would think that they would have a solution already in place.

Andrew

[demonpixel]

ok that's like the fourth time someone's mentioned the secondaries spring being too weak so i'm starting to believe that's it lol...looking at it, a really strong spring could do the trick. i felt how tight it was around the black rod, and there is a little bit of slop. is there supposed to be? this is going to sound stupid but how do you tighten that spring, because i tried removing that Phillips head screw and that thing would NOT come off!!

how common is it for these holley double pumper styles to have weak secondary springs from the factory??

[70bird]

Jeez, what a PITA this thing is for you!
I assume it is not possible for you to return it???? Exchange???

It is not common for Holley (I repeat HOLLEY) carbs to have this problem. After 25 years of playing with Holley carbs and swaping carbs to and from different vehicles, I have never seen this happen. I don't know if there is a stiffer spring even available. When I suggested a vac. related problem, I truly didn't believe this would be the case and just kind of threw that in there as something to rule out. It makes no real sense to me either.
As Andrew mentioned, there is equal vac/force on both sides of the butterflies.

Assuming the secondary spring is indeed too light, and that you can get a stiffer one, You will need to remove the butterflies from the shaft and slide the shaft out of the throttle plate to change the spring. THIS WILL VOID ANY WARRANTY!!!!!!!

Did you puchase this new?
I would exhaust my options of trying to return/exchange this thing, before taking it apart.

[andrewb70]

There is a critical difference between this throttle body and a carburetor. The carburetor uses a ventury. I am sure that this throttle body has a straight bore. I don't know how this effects anything, but I al just throwing it out there.

Andrew

[amx2334]

When you remove the link between the primary and secondary how much effort does it take to open the secondaries? From an open position the throttle blades should "snap!" shut.Not just gently close but snap.
Can you get that same view of the throttle body as it sits on the car? Maybe we can compare the two. I am looking at the spring to see if maybe it came off the tang.If there is no spring action the throttle will tend to open by itself.Just start an engine up without the return spring on it to see what I mean.

[demonpixel]

amx, i'll try to get you some pics of it on the car tonight. the return spring is still on the tang. to answer your question, with the car off and no linkage on, the secondaries DO snap shut when i let go after opening them.

just got off the phone with retrotek. they said that my vacuum is holding my secondaries open, and they said they are sending me a stiffer return spring and a phillips screw, and to uninstall the one that's one the tb now i need to undo the driver side phillips screw. that thing is on there TIGHT. they said to just use any means necessary to get it off, brute force, vise grips, etc. in the pics i'll post to you tonight, you'll see that i've already stripped it some.

they also said if getting the screw off doesn't work, they'll send me a new throttle body.

i'll keep ya updated, as always...

[demonpixel]

here are the pics. i included a pic of the car in case you guys wanted to see that also. definitely a work in progress

[Hammered]

Zig,

That throttle cable looping under the secondary linkage doesn't look good. I would move it out and away from the linkage. I would attach it where the ball stud is now.

This realy sucks - I hope you get it fixed. Slop in the spring sounds like the problem maybe.

John

[demonpixel]

John, I took the throttle cable off the ball stud because I thought it'd be better to see the linkage when I took the above photos. :) Don't worry, that's where I connect it when I drive it!

[demonpixel]

Well, I came home yesterday, grabbed a set of pliers, and lo and behold, I wound the secondary return spring not once around the black rod, but TWICE. It was MUCH tighter after that.

I hooked up the Holley 1:1 linkage from Summit I got, and said f it, I'm going to drive it. Drove it around and got on it, no problems! That 1:1 linkage REALLY makes a difference too, there is no slop anymore (nice and snug) and accelerating from idle to cruise is really smooth. From cruise to a dead stop, the secondaries came down just fine. :woot:

I'm going to keep an eye on it and see how it does on highways but it seems like the car is ok for now.

Oh, another thing I did, was I chose a different profile setup (just to see what would happen). It was for a smaller cam and a little less torque than the profile I was using before, and it ran better. More accurately I should say, I like the way it runs better.

Thanks again guys for checking back and giving input, all of it definitely helped!

[70bird]

ALRIGHT!!! :twothumbs