Vapor lock

[ugly74]

Howdy all,
Today I drove my bronco on pavement for the first time in well over a year, and it was its first real trip with my 351c. Ran sweet. Tons of useable power, and I’m pretty stoked about it.
Except for it’s wanting to starve for fuel if I sat in one spot too long, or just puttering around town... and it did eventually die while it was idling and I was jawing with a neighbor for like 15 minutes.

Bottom line, the fuel line between the pump and the fuel valve is way too close to my headers, and I need to fix that.

What all have any of you done as far as rerouting, shielding or insulating the fuel line?

I’m half thinking I could bend up a steel line to route inside the frame...

Any thoughts or ideas on that?

 

[blubuckaroo]

When you add dual exhaust, the pipe is going to be closer to the fuel line.
I ended up putting an electric fuel valve back in front of the rear axle, and ran the fuel line outside the frame rails.
That fixed the vapor lock problem.

 

[SteveL]

I say reroute it. I had problems with it years ago. I tried different insulation and wraps without much luck.

 

[bronconut73]

If you run an electric pump you can run the fuel line outside the frame rail then up the firewall behind the drivers side fender straight up to the carb never having to go by the headers.
But if you're still running a mechanical pump then you still have to go by the headers to get to the mech pump. But at least running on top of or outside the frame will keep the fuel line away from the exhaust.

 

[Rustytruck]

what carb are you using? do you have the thicker insulating gaskets under the carb. I use a fuel line insulator from the pump to the carb. I also have header wrap on the front half of the exhaust system. try to reroute hoses and stuff from the sides of the engine to unhinder air flow. the only place for air to move under the hood is between the sides of the engine and the inner fender liners.
fuel line insulationhttps://www.summitracing.com/parts/hsp-204012

 

[ugly74]

I haven’t torn into it yet to see how exactly I’m going to do this.
It’s a holley 650 double pumper.

I think my trouble spot is ahead of the firewall, behind the steering box. Headers are way way closer than my 302 headers were, and that spot also has a negative pressure, so it’d flash off to vapor sooner.

I was hardened against an electric pump, but as soon as bronconut said it, I thought again. Routing would be easy, and the fuel would definitely stay cooler overall.

 

[blubuckaroo]

If you run an electric pump you can run the fuel line outside the frame rail then up the firewall behind the drivers side fender straight up to the carb never having to go by the headers.
But if you're still running a mechanical pump then you still have to go by the headers to get to the mech pump. But at least running on top of or outside the frame will keep the fuel line away from the exhaust.

If you run a mechanical pump, you can run the lines outside the frame too.
That's what I've done. I really don't like electric pumps!
I put an electric "tank valve" right ahead of the rear axle. That way both main and aux tank suction lines are close to the same length.
Mine was plagued with vapor lock, but now it's been cured.

 

[ugly74]

I don’t really want to run the fuel line outside the rail. I’d really rather not leave nothing in between it and the tire. Tire chains in the winter, and brush, tree limbs and rocks I climb over (forestry roads, high deserts, and my yard) make me think I want it better hidden from the wheel well.
There are oblong holes in the top of the frame where I could drop the line into at the rear, then back out at the front very near the pump. It’d be protected and cool!

But the more I think about it, the more I’m liking the idea of mounting a 12v pump, and running the line up over the trans to the carb.

I’ve never been a fan of electric pumps, just because I’ve seen a lot of them fail with little to no warning.

 

[ugly74]

Just now looked, and there’s plenty of room to flip my dual inlet line over, and have it pointed to the rear! I’m going to go pick up a pump tomorrow (after some cursory research)
I even already have a holley PRV from another project, just in case I have to tweak the inlet pressure.
Now I have an excuse for a hidden switch!

 

[blubuckaroo]

Just now looked, and there’s plenty of room to flip my dual inlet line over, and have it pointed to the rear! I’m going to go pick up a pump tomorrow (after some cursory research)
I even already have a holley PRV from another project, just in case I have to tweak the inlet pressure.
Now I have an excuse for a hidden switch!

I think you are probably on the right track to switch to an electric pump.

I noticed that you live in CO.
Vapor lock is usually caused by a combination of heat and high elevation. Liquids boil at a lower temperature at higher elevations.
Since you're moving the fuel selector valve, why not just mount an electric valve back by the tanks along with your electric pump?

 

[ugly74]

I didn’t move the valve.
I went to Napa and got a 3-5 psi pump, and mounted it very near the tank valve, made a hard line to run up the back of the trans, and hooked it to my (now backwards) dual inlet fitting. It fired right up... no leaks! And I’ll drive it to work tomorrow with my brandy new 31” Cooper ATPs.

 

[ugly74]

Drove it to work without a hitch. Ran great, still no leaks. So that’s nice.
The pump started gettin noisy as hell and I thought wtf is this new BS.... ooops tanks empty! Switched tanks, and it went back to silent running.
So that’s a bonus, an audible low fuel warning!

 

[bronconut73]

Ha.

Yea I've noticed mine gets a little louder when running low.

Glad you are back in the saddle Sir.

 

[ugly74]

Ha.

Yea I've noticed mine gets a little louder when running low.

Glad you are back in the saddle Sir.

Hey man, thanks for the suggestion. I had automatically excluded it as an option before I even really thought about it. But, it made perfect sense, as it addressed all of my points.

But just so we’re clear; when that pump fails, I’m blaming you!;D

Well gang, I think this wraps up another mystery