Yes Sir; Will someone please explain the reason you would need to hook the return line from the fuel pump to the tank.?? (&) Where at the tank area would you look to make sure that it is hooked at tank area?? Thank-You Gene

 

FYI...Always give your year model. There is a huge difference in technology from a 1968 to a 1982.

What year is your Corvette????

GM decided that any unused fuel that the engine was not needing and the fuel pump was providing to the engine went back to the fuel tank so the fuel was just not sitting there in a fuel line getting 'stagnant' and allowing it to get hotter and hotter....and possibly causing for performance issues.

AS for WHERE to look depends on your year model because they are different from 1968 to 1982.

DUB

 

Thank's Mr. Dub. I have a 1982 & 1977 Corvette. I am working on my 1980 El-Camino with a 454 Cu. inch engine. I have both manual & electric fuel pump. What is happening is that when I run on just the manual pump, after a few miles 30 plus / minus a few, it will run out of gas in the carb & just quit running even at freeway speeds. Loss of all power, brakes, Steering & engine. Not fun trying to get out of the way at ( 70 ) MPH. Needed to change my clothes the first time. LOL I just installed the new manual pump & blocked the return line. I kick on the electric & it restarts. Gene Thank's.

 

The return line is there to prevent the symptoms you are having, vapor lock.

 

After 1974 all gas caps were non vented because the tanks were. So blocking that hose can and probably will vapor lock the fuel system...

One other thing it can do is suck your fuel tank down as well. So if you are pulling fuel and not venting the tank it can collapse.

Willcox

 

Vapor lock happens in the supply line to the mechanical fuel pump because the supply fuel gets hot enough to turn to vapor (boils), especially when under negative pressure. The return line lets some of the fuel from the pump return to the tank and in turn keeps the fuel in the supply line moving so it doesn't absorb as much engine heat and cause the vapor which the mechanical fuel pump cannot pump.
When you turn on your electric pump, it pressurizes the supply to the mechanical pump and it starts pumping liquid again.
The easy fix is to get the correct 3 line mechanical pump and re-attach the return line.
Your fuel tank should be vented through the carbon canister via a line on the drivers side of the frame.

 

I do not work on El Caminos...and I do not know that when the 454 was put init...because I doubt that it came factory that way....like I said..I do not work on them. And IF your headers or exhaust is close to your fuel supply line coming from the fuel tank...you might want to invest in some time and money to create a heat shield to keep the heat off your fuel supply and return lines.

The El Camino HAD TO have a fuel return line because the year model it is and it also HAS TO have a vapor line to the charcoal canister.

As suggested...I would look at your fuel pump and make sure it has 3 ports on it. IF not...change it out AS long as you still retained the fuel return line.

Also.not knowing how 'crazy' your 454 is...I have had some guys switch out the entire fuel line on some Corvettes that were rather serious big blocks and installed a 1/2" fuel supply line.

I have seen the rubber hose from the steel fuel supply line get sucked shut due to the incorrect rubber 'S' hose was not used and it would stave the engine for fuel...but that usually occurred when they were getting on it rather hard....but it would do fine when they were idling or right off of idle.

AS for your fuel cap...unless you changed it...it should be made so air can be drawn into the fuel tank through it but NOT allow vapor to go back out through the fuel cap. Becasue IF the fuel cap can not allow air to enter the fuel tank and all provisions are working as designed....when the EVAP system is working and fuel is being pulled into the carb...the suction on the fuel tank CAN collapse it like Willcox mentioned.

DUB

 

only in and out on this one, I have the return on a long hose up to the recovery tank plugged off, 77 with a bladder tank. hmmm, have not had any trouble, still takes same amount to fill the tank

 

On my 68 if I take off the gas cap while the engine is running, I can see the stream of gas returning to the engine. Looks like if you had a garden hose stuck in a tub of water- quite a lot of turbulence.

 

YEP..I have numerous customers with a fuel pump with one in and one out and do not use a fuel return and they have no problem either....and to be honest...the new Corvettes have a fuel return but it is all the way back by the fuel tanks and NOT up at the engine.....so the fuel line going to the engine has stagnant fuel in it that is NOT circulating.....BUT...those cars have had the fuel line protection taken into account...so this El Camino in question may NOT be the same way....thus....potential vapor lock.

And obviously the amount of fuel to fill up your tank would not change...so I do not know what you meant by that.

DUB

 

Thank's to you all for answering My Questions on the El Camino. I think you hit the problem on the fuel boiling, The Tank was collapsing before I changed it to a vented cap. I still don't have any idea of where the return line should be hooked in at.??? One of my friends told me to just run the electric pump & forget about the manual. For some reason I still would still like to fix the whole system. I'm looking for a Charcoal filter with just two openings, in lieu of the five to also hook that part of the System up Thank's for all your help, Gene

 

I have a vented cap that I looked at, I also put a check valve on the return line up by the recovery tank for tank venting, the reason for same amount of fuel is if the tank was being sucked in from vacuum without a vent

 

The fuel tank on your El Camino will have a fuel return more than likely made into it. Being a 1980...I would BET it has one along with a vapor line. You might need to get on another forum who may help you or drop the fuel tank and find it. Call a supplier that sells El Camino parts and they might know.

DUB

 

I installed a new tank & sending unit. only outlets were for the Charcoal filter & the main feed line. Just to let you all in with a secret. Corvette Forum is wonderful place to find almost anything from the Knowledge of it's members. I have found More help from it's members, than anywhere else on the internet. Thank's Guys, I Appreciate. Gene

 

Gene,
I do not mean to come a cross doubting your but either they sent you the wrong fuel tank or sending unit because something is WRONG.

Your fuel tank should have at least 3 ports. One being fuel delivery to your engine...the other being fuel return..and the last one being vapor.

You DO have an actual fuel return line on your frame...don't you???

DUB