Hot Fuel Lines

-
rod7515

rod7515

Well-Known Member
Joined
Jul 18, 2013
Messages
1,747
Reaction score
595
Location
Red Lion PA
Was wondering if anyone else has ever ran into this issue. Im working on my 66 Dart with a 408. With the build I did I replaced the factory fuel lines with 1/2" aluminum lines and added a return line back to tank. My system goes from tank and runs up the inside of the frame connectors. Then it goes up into the engine compartment past the oil filter area on the inner fender. Runs up the inner fender to the front where it goes into a regulator. From the regulator it goes to the Carb while a second line runs from the regulator back to the tank right beside the delivery line.
My exhaust creates to much heat for these lines that it starts to vapor lock the fuel from feeding up the line. It doesnt start until after I go about 10 miles and then if the car sits it wont start back up until it cools off. Ive hit the fuel lines with my infra red and they get as high as 140+.
So I ordered some heat reflectant wrap that is good to 1100* and Im going to wrap the fuel lines. My exhaust is closest at the muffler where the clearance is about 4" away. The extensions pipes are probably 12" or so away.
Ive added 2 pics of the underside so you can see the fuel lines. Let me know if you think covering the fuel lines will help this or do I have to try something else.
Rod
DSCN1525.JPG
DSCN1523.JPG
 
I've seen a LOT of people run the fuel line right into the frame rail around the header and back out the frame rail into the engine compartment. Just a thought. Also, what fuel pump do you have? Electric I assume as nice as the rest of the system looks. Are you 100% sure it's vapor lock? Usually with a good electric pump and a return line, you kiss vapor lock goodbye, because the fuel is constantly circulating and hasn't a chance to heat up to that point.
 
I agree with RRR, beautiful set up BTW, I dont think the lines in the picture are close enough to vapor lock. Vapor lock is usually a problem with mechanical pumps at there suction point when pressure drops. 2 questions..
Where is your fuel pump located?
What are you running for fuel pressure?
 
Nice underneath.

Had the same problem with a Dodge dually with headers. I tried foil, differant pumps, bigger lines the only thing that fixed it was I moved the line to the outside of the frame rail.
No more problem.
Need to see a picture of the outside of your car.
 
Not to be a stick in the mud but it looks like you have created other issues for yourself also. I notice you have a driveshaft loop installed which could mean time at the track. I also notice that you have an automatic transmission. I wont quote nhra rules (maybe you don't run at sanctioned tracks) But I would suggest taking a look at the fuel line rules, not only so you meet rules if you need to, but also because some of them make sense.

On the other side. I don't see how you are generating that kind of heat in your fuel line. You would almost have to have a couple of feet of your line damn near laying on your exhaust to get there. When you get the 140+ reading. Did you take a tank reading? I think your heating your fuel through the pump and line and maybe picking up some exhaust heat and then cycling it back to the tank. Pressure creates heat. Over pressure creates a lot of heat. If your running a super high pressure pump and cycling most of it back to the tank and then only pulling what you need from the regulator to run what? Something around 6 or 7 pounds pressure? Your fuel gets hotter and hotter every time it cycles. And I still don't read that as vapor lock. You have to heat the fuel to the vapor point to create that issue. I'm not seeing it.
 
Some answers to your questions, Yes it is a mallory electric pump and regulator. The mounting position is below the tank as instructions say it must be.
IMAG0323.jpg

Jadaharabi, heres the outside of the car and also you can see how the pump sits,
20190404_174727.jpg
20190404_174718.jpg
20190404_174740.jpg

A408cuda, Fuel pressure starts at 6.5-7 when its first started up, but once it starts to do its what I think is a vapor lock its drop to about 5 psi. You will feel the car start to hesitate when pulling out or feeding throttle. Then if you shut the car down and it sits for 10 minutes or more it wont start unless I drop accel to floor and crank for about 10 seconds.
Blindsquirrel, Im not sure what rules you are concerned with but yes the car I hope will see track time at some point. There is no rubber line in the system at all, its all braided or solid and it does not go up the firewall at all. It does get close to the header collectors but I dont have any pics of that. That will get some of the shielding.
DSCN0562.JPG

I was able to find this pic of the engine compartment fuel line routing.
I will be traveling home today so wont get to check my email or reply back until later tonight. Thanks for all the responses and I hope to resolve this issue soon with your help.
Rod
 
Great looking car.
Covering the lines at the collector, I don't think will do any good. I tried that. It didn't work for me. I had to get the fuel line basically out of sight of the exhaust.
Your line is within inches of the collector and the header pipes. You need to move that out of there.
 
Last edited:
In the first picture the collector is cooking the paint on the front cross member and the lines are right there.
 
Beautiful car and craftsmanship..... Not sure why you are having the problem. Everything looks to be in order. I am sure you are tired of chasing to dollar to solve the problem but an In tank would be a nice setup on your car.

Are you sure the pump is OK? Also, are the lines a matched diameter for feed and return? The 2 cars I have done a return deal with had smaller return than feed lines. It may not even make a difference but just putting it out there. As RRR said, a return will shut down Vaporlock.....

JW
 
Well guys, I do not think the problem is vapor lock.
I think the carburetor is percolating and flooding the motor.
 
Beautiful car. Love the execution. I think you might be on the right track after looking at the cross member like jaba the hut pointed out. I would do everything in my power to relocate that section of fuel lines. Into the frame, through the frame to the outside of the frame (IF NHRA allows), whatever I could do. I don't think fuel percolation at the carburetor is possible with that intake. It has no exhaust heat cross over provision. Sometimes they even ice over. I've had a few do it. That said, I guess it wouldn't hurt to run the thick carburetor insulator gasket. Maybe that coupled with relocating the fuel lines will get it solved.
 
Oh and I didn't include this........but I would NOT wrap them with anything. Look what the heat is doing to the cross member paint. I don't care how "burn proof" something is, that right there is gettin HOT. Now.......Maybe a custom made sheet metal shield over the lines in that area, I could endorse.
 
This is a very nice set up, people run it all the time. I agree with Donnie514, I would suspect carburetor is purcolating. Also, I try an minimize fuel routing in engine bay and or near the engine due to heat transfer, like the green setup in the picture. (Less cost, fittings, and heat transfer)

The main line coming up is usually close to headers, I wrap that as well or run it from inside fender well with bulk head connectors to the regulator on the firewall. Moves it and helps keep it outside frame rail when you route it from the exhaust. Trouble spot is back by the tires/wheel, rear well when going back to the tank.

Screen Shot 2019-06-23 at 7.19.18 AM.png


File_001 (6).jpeg
 
Last edited:
Cazbah362 said:
This is a very nice set up, people run it all the time. I agree with Donnie514, I would suspect carburetor is purcolating. Also, I try an minimize fuel routing in engine bay and or near the engine due to heat transfer, like the green setup in the picture. (Less cost, fittings, and heat transfer)

The main line coming up is usually close to headers, I wrap that as well or run it from inside fender well with bull head connectors to the regulator on the firewall. Moves it and helps keep it outside frame rail when you route it from the exhaust. Trouble spot is back by the tires/whee, rear well when going back to the tank.

View attachment 1715354071
Click to expand...

You do realize that any fuel system on the firewall is not NHRA legal? They will tech you right out of the track.
 
Rusty - understand, then move it to a sanctioned spot with less travel and less time to transition heat by the engine or exhaust. Note, so is running next to the header.
 
rod7515 said:
My exhaust creates to much heat for these lines that it starts to vapor lock the fuel from feeding up the line. It doesnt start until after I go about 10 miles and then if the car sits it wont start back up until it cools off. Ive hit the fuel lines with my infra red and they get as high as 140+.
Click to expand...

rod7515 said:
Fuel pressure starts at 6.5-7 when its first started up, but once it starts to do its what I think is a vapor lock its drop to about 5 psi.
Click to expand...

Vapor can lock up fluid flow in a couple ways.
On the upstream, positive pressure side of a pump it will be a vapor pocket at higher pressure than the pump. That blocks most flow to the fuel inlet unless it can burp out. Early 60s Chrysler took extra measures to insure vapor could always excape the outlet of fuel filter to the carb bowl.
Hot restart vapor problems were from excess fuel in the bowls (ie flooding) after shutting down.
With your pusher pump setup I wouldn't expect exactly the same type of vapor issues, but knowing the characteristics may help you narrow it down.

Let me throw some ideas out.

The aluminum hard lines are not helping. Tarmack is easily 100*F in summertime Aluminum has very good heat transfer characteristics. So in this situation, insulation is almost certainly going to be a help. I'd use the insulated firesleeve for the entire length of the line. Then cover or shield in something reflective.

If that paint discoloration on the cross member is from heat, then do whatever you can to reduce the heat off the collectors. Wrap them in zircotec foil or something.

You might find my grilling experiment halfway down the link of some interest.
What to do about Winter Fuel in hot temperatures?
(if there any annoying requests by tapatalk, ignore them)
 
Last edited:
Is the tank vented?

The part of the rule to look at is where your line passes by your converter area. It has to be braided line or outside the frame rail, or encased in a steel tube 16" long 1/8" thick.
 
My two cents worth, aluminum adsorbs heat, stainless steel rejects heat, plus its easier to damage aluminum lines. Maybe changing to stainless steel would cure your ill.
 
Pardon my ignorance. How can a pushing fuel system vapor lock?

Oops! Just read Mattax's post 17.

Never mind!
 
Last edited:
Dana67Dart said:
Pardon my ignorance. How can a pushing fuel system vapor lock?
Click to expand...
When it gets heated enough for vapor pressure to equal maximum pump pressure.

upload_2019-6-23_14-36-39.png


if it can get out the carb vent, that greatly helps.

I'm not sure how predictable things are if it gets really bad - which can happen with fuels that are allowed high RVP.
upload_2019-6-23_14-48-32.png

You'ld think it would all escape, but maybe not if the heat is there and the fuel keeps vaporizing.
And if its forcing the needle valve open, then what's happening to the fuel level?
Finally, what's become of the fuel that's in the bowl and going into the intake?

The last I can make an observation about.
This is screenshot from a datalog where I removed the air cleaner lid while idling (yellow markers on timeline). (Summer 2011)
Recording time in min:seconds along bottom.
313_b80f51ebb906978483d77636a5cd3ab2_t.jpg


archived discussion from that time.
'Sasquatch' seen some similar phenomenon.
Why is the Air Cleaner changing Idle AFR?
I was doing more fixing than driving that year so it could have had winter fuel or some old fuel or both. Didn't think about that or maybe even know about the differences then.
 
Now that i think about it this does explain the odd clear fuel filter phenomenon i video taped and posted a while back. My stock dart had a clear filter. I noticed that the filter would go empty then refill just as the rpm started to drop off. I put a guage on it and the pressure maintained till it started to refill.
 
A couple more thoughts about what happens to the remaining fuel.
The portion vaporized was the portion that helps initiate good combustion. If it doesn't get sucked into the combustion chamber as vapor (like when I took the top off the air cleaner) then its like trying to start a campfire without tinder.

Also if the fuel is partially vaporized before it hits the bowl, then its not getting pushed through the carb's passages...
Lets say the fuel actually hits 150*F at some point and the fuel distillation curve looks like the E-8 here, then 30% of fuel is vaporized before it gets to the intake!
upload_2019-6-23_17-19-56.png
 
A few more answers to some of the questions that have come up. Yes the tank is vented with a 1/2" aluminum line. The dark marks around the trans mount is not the paint being cooked but that was fom when I first started the engine and did not have any exhaust behind the headers. I will be repainting that area in the next few weeks but I dont think that will return unless I run no pipes again. As for running a plate under the carb I have added a kool keepers insulator a few weeks ago when I first found this issue. Next would be the fuel percolating and yes I believe that could be possible. I did hit the bowls with the infra red thermometer and the front bowl was at 151* while hte back was at 145* and that was with the insulator on. The carb is a Sean Murphy built carb, 750 reworked to flow at 830* cfm if I rememeber correctly.
So tonight I plan on installing the wrap around the lines and I will start looking for someone that sells a guarding to cover the lines as well. I may have to try to make a guard cover!
I will keep you updated on what I find.
Thanks Rod
 
You must log in or register to reply here.
-

Back
Top