Adding a return fuel line...

[TrunkMatt]

Thanks to a few repeat visits from uncle vapor-lock, I have decided that I probably should add in a Fuel Vapor return line back to the tank.

 

Most the montes I see have one... but mine does not. Crawled under, and there isn't even a return line in the frame.

 

Now for my question:

 

I see some montes that have the return line off the fuel pump... and others that have it off the filter near the carb (which makes more sense to prevent vapor lock).

 

I am imagining this lowers fuel pressure to the carb some... so what all should I be looking to install????

 

Is there a fuel pressure or vapor regulator that also sits inline on the return line that enables the return to only work over a certain PSI?

 

I know the vapor return lines are smaller, but I can't help think if it is all setup wrong that I'll be starving my engine.

[Big Jim]

I was talking to a friend last night about that very thing and he said if your fuel line is touching the heads or intake that it is heating the gas and you need to get the line off the engine he also said there is a fuel line insulation you can get and cut to fit and that should take care of it.

[dbreese]

Hi Matt,

 

Are you running a stock carb setup or do you have an aftermarket? (Holley, Edelbrock). You might be able to solve your vapor lock issues by adding a phenolic spacer(heat isolator) between the manifold and the carb. Give that a try first before going through the issues of running a return to the tank. BTW my 72, when stock, didn't come with a return line but.... it could depend on where your Monte was built.

 

David

[TrunkMatt]

I have a stock 4bbl Quadrajet sitting on top of a Edelbrock manifold.

 

I don't know where the lock is occuring, a the pump, the line near the engine, or the carb itself.

 

I honestly am suspecting my Vaporlock issues are occurring in the line itself leading to the carb... as it wasn't run past the waterpump like most metal lines (mine runs behind the alternator and touched the engine block at one point... I bent it away and am hoping it helps)

 

 

Really, I suppose I could just go with an electric pump in the tank - remove the mechanical, and run a positive pressure system thus eliminating the issues... I am okay not having a 100% stock engine bay.

[dbreese]

Matt,

 

If I'm not mistaken I think someone makes a heat shield for the Q-jet. May be aftermarket or reproduction piece.

 

If you go to an in-tank for a carb it could get very expensive. I have a external electric fuel pump with a return style regulator. The lines, -8, alone with a few extra fitting where about $350.00, pump was $230.00 and the regulator was $100.00. O yeah the sending unit is a Robbmc 1/2" feed and return another $150.00. This was bought over the course of about a year and a half. This stuff adds up quick!!

 

David

[wallaby]

Vapor lock usually happens on the suction side of the pump, and where it is close to a heat source. just like a cooling system, the boiling point is raised when it's under pressure.

 

Is it possible that you have a defective/wrong fuel cap? maybe the charcoal canister lines have been removed or plugged off?

You can pull a vacuum in the tank if it can't breathe and no fuel pump will be able to pull fuel out of it if that happens.

 

another option is a clogged fuel filter in the carb inlet behind the fuel line fitting.

[TrunkMatt]

Well, I only got the vapor lock while in Boise, which is 4,900 ft higher in altitude than where I live in Oregon... and it was also about 95 degrees the day it happened.

 

Here in Oregon, it doesn't happen unless I am sitting idling in the sun for 30 minutes.

 

Runs fine on the open highway / any situation when it gets plenty of gas... V-Lock only seems to occur when idling at long red lights (some were 3 minutes) in hot weather, at altitude.