[i82much]

I had some issues with the car wanting to stall and the wideband showing a really lean condition on a hot day recently. I noticed there is a metal fuel line that runs basically right in front of the engine block up toward the carburetor. I have a carter mechanical fuel pump.

I can't see anywhere else besides the front of the block where the fuel line is going to pick up that much heat. Does it make sense to wrap that section with some heat shield? I am not sure I will be able to pull the fuel line that far away from the block, I think the heat shield is going to be touching the front of the block. Does that matter?

[Schurkey]

Heat-shielding on the pressure side of the pump is unlikely to hurt. It's also unlikely to help, but what the heck.

"Vapor lock" happens IN the fuel pump, or in the fuel tubing on the suction side of the pump.

By the time the fuel gets to the pressure side of the pump, and the plumbing up to the carb, vapor lock isn't generally an issue.

Does this pump have a vapor-return tube? If not, that's where you should start if this really is a vapor problem.

[i82much]

Thanks Shurkey. There is no vapor return ... this only happened after I switched from pure gas to E10, so maybe I'll just go back to pure gasoline for now. Sooner or later I want the car to be able to drive anywhere on whatever I can find at the pump wherever I happen to be, but for now I'm not taking any road trips and pure gas is available locally.

[ID67goat]

Had the same problem and tried everything…..insulating fuel line, vapor return, etc.

Only thing that really worked was installing an in tank fuel pump with return style regulator. Just my experience, but the only way to prevent vapor lock for me was to pressurize the fuel to raise the boiling point.

[Holeshot71]

Originally Posted by i82much

I had some issues with the car wanting to stall and the wideband showing a really lean condition on a hot day recently. I noticed there is a metal fuel line that runs basically right in front of the engine block up toward the carburetor. I have a carter mechanical fuel pump.

I can't see anywhere else besides the front of the block where the fuel line is going to pick up that much heat. Does it make sense to wrap that section with some heat shield? I am not sure I will be able to pull the fuel line that far away from the block, I think the heat shield is going to be touching the front of the block. Does that matter?

Make sure you don’t have a cylinder misfire. That will show a lean condition on the AFR gauge. Also check for any vacuum leaks.

[i82much]

It was fine running pure gasoline, so i will just switch back to that for now. Thanks all!

[78w72]

The factory used a insulator on that line from the pump to carb for some cars like 2nd gen firebirds so Im sure there was a reason for it, its just a 1/4" thick foam rubber material so not sure how well it actually worked on a fully heat soaked car in hot summer temps, but they found a reason to use it so it most likely has a benefit.

I have a robbmc mechanical pump in a dead head set up on a 500+hp engine with a Q-jet, I use a 1/2" or -8 braided line from pump to carb & have never had a vapor lock or over heated fuel problem using 10% ethanol or straight gas, hot summer days on the street or at the drag strip all day... and my line from tank runs on passenger side & comes about 2" from the big header tubes, then crosses over to pump under the front of engine clamped to the front oil pan bolts, so it gets pretty hot compared to cars with fuel line on driver side.

Even though I didnt have issues for a few years, I decided to put some heat wrap on those hot areas just to be safe, i use a heat tape with adhesive on the back to wrap around the line in tight spaces, or use a heat wrap summit sells with velcro down the side so it can be slipped over line without disconnecting them, seems to be good stuff and im sure it reduces the temps, the line from the pump to carb is still bare since its kinda floats around behind the p/s pump & alt so its not touching the engine... but heat wrap can touch the block without any issues.

Heat tape/wrap is cheap enough to try and definitely has a benefit in key areas.

[JLMounce]

Originally Posted by i82much

Thanks Shurkey. There is no vapor return ... this only happened after I switched from pure gas to E10, so maybe I'll just go back to pure gasoline for now. Sooner or later I want the car to be able to drive anywhere on whatever I can find at the pump wherever I happen to be, but for now I'm not taking any road trips and pure gas is available locally.

E10 has a lower boiling point than pure gasoline, by a decent margin actually. As altitude increases it gets worse.

If you have access to pure gasoline without making your life a headache, and that cures the issue, I'd just do that.

As mentioned already, the vapor lock will tend to happen in the fuel pump, or in the carb if it has a large bowl and you are trotting around at very low speeds, or idling.

Phenolic spacer on the carb as well as a phenolic insulating spacer between the block and the fuel pump can help, but the problem is that in many locations the boiling point of e10 is below 180 degrees. If you run your engine around 180-200 as seems somewhat typical, it's really only time you're buying.

The sure fire cure is an in-tank pump with a bypass regulator and a return fuel line. Then, you can typically run any fuel you'd like.

[i82much]

Ok, thanks everyone! I will insulate the fuel line, switch back to pure gas, and then maybe upgrade to an in-tank pump with return line one of these days!

[hurryinhoosier62]

Originally Posted by i82much

Ok, thanks everyone! I will insulate the fuel line, switch back to pure gas, and then maybe upgrade to an in-tank pump with return line one of these days!

Find some Aeroquip fire sleeving for aircraft flammable liquid hoses. It’s a bit pricey, but is superior to most other stuff you can find on the Internet.

[PAUL K]

DEI (the normal DEI) Fire Sleeves work great.