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-   -   Using TBI fuel pump with return reg on carb (http://www.hotrodders.com/forum/using-tbi-fuel-pump-return-reg-carb-215154.html)

brad33478 02-22-2012 10:37 AM

Using TBI fuel pump with return reg on carb
 
I am using my stock TBI in tank fuel pump for my carb, I am using a Holley fuel regulator with return back to the tank. My question is it necessary to bypass all the evap canisters next to the tank? If so will I need to run a new vent for the tank or should the cap breathe enough?

Thanks
Brad

Off a 2006 chevy 1500

brad33478 02-22-2012 05:53 PM

well i unhooked the return line right before the evap canisters and ran a hose into a pan.

when i turn the key on the pump kicks on like normal and spits fuel through the return line but then shuts off after a second.

is this normal? or should the pump be consistently running and returning fuel all the time?

FmrStrtracer 02-22-2012 06:27 PM

If you are running the pump off the original EFI circuit, the computer shuts the pump off after a short run unless it see's a tach signal that tells it the motor is running.

LATECH 02-22-2012 06:27 PM

Quote:

Originally Posted by brad33478
well i unhooked the return line right before the evap canisters and ran a hose into a pan.

when i turn the key on the pump kicks on like normal and spits fuel through the return line but then shuts off after a second.

is this normal? or should the pump be consistently running and returning fuel all the time?

The pump is running for a second or 2 as the ecm is energizing the pump relay to prim the system. Once the engine starts the oil pressure switch should close and power the fuel pump circuit.My geuss is that you left the oil pressure switch out of the loop, so only the prime part of the circuit is functional.
You can vent a cap,but It is smarter and not real hard to keep the evap system intact. It will keep the fumes from taking over your garage.PLUS a sealed system with an evaporative setup that functions will help keep the fuel fresher as an open vented system allows moisture in, which is absorbed by todays fuel because of all the ethanol in the fuel, which is hygroscopic(absorbs moisture/water) to an extent. Water dilutes the fuel and lowers the allready low octane.It will also rust your tank.

brad33478 02-22-2012 07:44 PM

I did keep the oil pressure sensor in the loop and RPM signal but I havent fired the motor up yet, just checking through things beforehand. So I will check that it is pumping while running later on.

should I just keep all the EVAP and instead of running the output back up to the intake manifold (like the original) just have it vented into the air?

I dont know a ton about EVAP but im assuming that all it does is relieve the tank pressure (fumes) when it becomes too high and releases into the intake to be reused instead of just into the air???

thanks everybody for the help

LATECH 02-22-2012 08:04 PM

Quote:

Originally Posted by FmrStrtracer
If you are running the pump off the original EFI circuit, the computer shuts the pump off after a short run unless it see's a tach signal that tells it the motor is running.

That is true on a ford, but this is a 06 chevy, oil pressure switch maintains the power to the pump after the prime signal from the pcm.
chrysler also uses the tach signal for keeping the ASD and fuel pump relays energized.

LATECH 02-22-2012 08:23 PM

Quote:

Originally Posted by brad33478
I did keep the oil pressure sensor in the loop and RPM signal but I havent fired the motor up yet, just checking through things beforehand. So I will check that it is pumping while running later on.

[ Quote should I just keep all the EVAP and instead of running the output back up to the intake manifold (like the original) just have it vented into the air?]

posted by Latech-[Quote Well the problem you will have is that the purge solenoid and canister vent/closed solenoid are regulated by the ECM. Part of the strategy used to run it depends on a few vital sensors now missing due to the fact you took off the Throttle body and put on a carb.The throttle posistion sensor is important , but now missing.Your carb doesnt have one.
The ECM needs to know the throttle posistion to properly regulate the purge flow(also other info is needed too ie: coolant temp,tank pressure/vacuum, etc.)
Defeating the emission devices is illegal, by removing the throttle body and replacing it with a carb, you made it quite difficult to keep the system functional. Quote]



[Quote I dont know a ton about EVAP but im assuming that all it does is relieve the tank pressure (fumes) when it becomes too high and releases into the intake to be reused instead of just into the air???

thanks everybody for the help

That is basically what it does, keeps the vapors from fuel from escaping so it can be used by the engine.
In the state you live you may not have emission testing or inspection, which means you may get away with defeating the systems,however I do not condone it. Also you are devaluing your vehicle by doing so, and without converting to a non computer ignition,like a basic HEI with mech /vacuum advance, you probably wont get it to run very well either.You have to have quite a bit of talent to take a late model EFI system and make it run better and perform stronger, it probably wont happen with just a carb and distributor swap.
not tryin to be an A hole about it, just sayin.

brad33478 02-22-2012 08:36 PM

well it was originally a 4.3l TBI and dist., which i never owned a v6 until this truck and i dont see why they bother even putting it into a full size truck, couldnt hardly move its on rear end. and barely squeezing 16mpg it wasnt worth its lack of power

its now a 383 stroker with HEI and holley

I wouldnt mind running the EVAP, just seems difficult to tie the original intake valve into the dual plane intake I have now. no emissions down here in FL

LATECH 02-22-2012 08:53 PM

I understand. The 4.3 was good but was anemic in a full size truck.
The evap should take care of itself, I would just put the hose from the purge valve inlet to the air cleaner,dont hook it to a direct vacuum source, just vent it into the air cleaner area,dont use the purge valve, just use a one way check valve, to allow pressure to go towards the carb from the tank.
A 383 should wake that turtle up into the hare it should be. :thumbup:
you will need to get a controller to run the 4l60E transmission though.
Like I said , it wont be easy.Or did you change it to an older 700 r ?

LATECH 02-22-2012 08:59 PM

Moved this to Modern Engine Electronics, seemed appropriate. Adresses conversion from MEE controls backwards to old school.

brad33478 02-23-2012 05:21 AM

I'm trying to keep the 4l60e currently with a carb tps kit from Holley and tach signal, the VSS is in the trans. I was told that's all the TCU should need for inputs. I also swapped over oil and temp sensors.

Thanks for the info on the evap that sounds like a good set up for me

brad33478 02-25-2012 07:40 AM

well i fired it up last night and the fuel pump wouldnt kick on, i have oil pressure gauge working but no tach, do you think it runs off the tach signal?

Jake_Dragon 02-25-2012 07:57 AM

Quote:

Originally Posted by brad33478
well i fired it up last night and the fuel pump wouldnt kick on, i have oil pressure gauge working but no tach, do you think it runs off the tach signal?

Does the pump come on at all? Did you disable the ECM or is it still hooked up.
My Vette uses the stock circuit so it runs the pump for 2-3 seconds then turns it off. My ECM is hooked up and I have the constant check engine light because of it but the car runs great.

brad33478 02-25-2012 09:25 AM

i kept the ecm but I have HEI ignition. the pump comes on the the few seconds initially then shuts off like normal, but onces the motors fires up it wont kick on. I have a working signal from my oil pressure gauge but cant find the right wire for my tach signal to the gauge.

on the harness for the old 4.3 distributor I had 3 wires. with the key on I have

Black/red - ground
Red + lower voltage around 10.5ish
Black/White which I get no ground or positive voltage from

I hooked the tach signal from my HEI to the black/white but still got nothing

If i have to i will just put in an aftermarket tachometer but i still dont know if the tach signals the fuel pump relay to turn on


At the HEI with the key on I am getting around 10.5 volts NOT running is this normal??


thanks
Brad

brad33478 02-25-2012 09:36 AM

Even though my old 4.3 was TBI it still had a crank position sensor, do you think this would cause it not to pick up a tach signal and also not allow the fuel pump to kick on?


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