Vapor locking once again

[The Neck]

Hey everyone,

I took the Roadster out over the last couple days and have consistently been having vapor locking issues. I have the stock hard line running from the tank to the area where the stock fuel filter is, and then 1/4" rubber fuel line running to a clear fuel filter, then another foot of rubber line, electric pump, a foot of rubber fuel line, then another fuel filter, then rubber line into the carbs.

"Overall" they follow a similar path as the stock lines. After a drive tonight, I pulled over as the sputtering started, and found gas to be boiling and flowing towards the tank in the clear filter closest to the tank.

I'm going to NAPA tomorrow and get 3/8 fuel line, and also reroute it so it doesn't even come close to the engine aside from the carb entrances.

Before I dig into this tomorrow, do you guys have any thoughts on my approach and set up?

Mike

[redroadster]

Coolant flowing - radiator blowing hot ?
One of those cheap infared thermometers is very helpful
In diagnostic

[The Neck]

Coolant is flowing, and I have consistent temps on the dot at 190 on the gauge.

I do have one of those thermometers, but I assume the under the hood temps are normal, where the actual lines are too hot.

[Nissanman]

Try wrapping the fuel lines in an insulator like this: -

260720151748 (Large).jpg

It has a self adhesive strip along one edge: you just wrap it around the pipe and peel and stick.
I have managed to do the complete length right back to the OEM fuel pump.

I don't know if the exact product is still available but Summit Racing would have an equivalent.
It fixed all of my heat related vapour lock problems in our HOT summers here in Oz


e.g. Summit Racing® Heat Sleeving SUM-350136-1
Heat Sleeve, Velcro®, 1,500 Degree F Rating, 40.00 in. Length, .500 in.-.875 in. I.D., Silver, Each

[The Neck]

I used that when I had the OEM hard line and was attempting to use both the stock fuel filter and fuel pump. It took one time getting stranded to make the jump, and the car has been running great ever since minus this recent vapor lock stuff.

I'm going to try a double approach since you mentioned that insulator and see if I can fix the problem with a reroute.

One other thing I noticed, was I'm having air bubbles enter the first fuel filter from some where between that and the tank. I'm thinking I need to re-evaluate the entire fuel line form he tank to the carbs.

[datsun65]

Mike, just on the off chance....

Try taking off the air filter base, housing and air filter. Give it a drive to see if it make any difference.

[The Neck]

Mike, just on the off chance....

Try taking off the air filter base, housing and air filter. Give it a drive to see if it make any difference.

I'm intrigued, but will do this first thing in the morning.

[GeoffM]

Mike, are you sure it's not that the pump is losing prime? Most electric fuel pumps like to push...not suck

[The Neck]

Mike, are you sure it's not that the pump is losing prime? Most electric fuel pumps like to push...not suck

I'm also not ruling this out.

Couple issues that I found yesterday.

I'm having air bubbles in the line, and seeing them in the first clear fuel filter. Sometimes the filter is completely empty, and the second one is following suit. My thought with this, is if there's air that is getting in the carb, the float will just request for more fuel to be delivered regardless. Would this also be a problem on top of the potential for vapor locking?

[GeoffM]

Mike,
the more i think about it, I'll bet that there is a combination of factors causing your vapor locking...all pump installation related. Also, because you're in Denver, you're missing 2psi of atmospheric pressure, reducing the suction head the pump sees and reducing the vapor pressure margin of the fuel. So, IMO, a combination of high temperature in the engine bay, lower atmospheric pressure, high suction lift (assuming the pump is mounted on the inner fender shelf and not down on the frame) and long suction run which increases dynamic pressure losses in the fuel line is contributing to vapor lock in the pump.
It's probably ok until the temperature part of the vapor pressure equation gets too high once you run for a while. Just some thoughts.

[The Neck]

Since this is looking to be more of a pump issue at this point, what would be the preferred way to install the pump? Would it be best to install right at the fitting that is coming out of the tank?

What are some common ways people have integrated an electric pump in their cars? It's a 67.5 and has no return lines.

[Datrock]

Just to eliminate the possibility of having a non venting fuel tank cap or seal creating resistance, loosen your gas cap to allow air in to see if the electric fuel pump will work better with your setup.

[devo]

Since this is looking to be more of a pump issue at this point, what would be the preferred way to install the pump? Would it be best to install right at the fitting that is coming out of the tank?

What are some common ways people have integrated an electric pump in their cars? It's a 67.5 and has no return lines.

Mine is frame mounted in front of rear wheel. Works like a champ.

[Nissanman]

So, is it heat related vapour lock or air getting into the fuel lines somehow?

[The Neck]

I talked to another forum member today for a little and ran him through the fuel system I have and he very quickly pinpointed the issue as the incorrect fuel pump in the incorrect location. I've got the pump and everything in the works and will post up once I get everything together.