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overheating causing fuel pressure loss

brncofinatic

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Jr. Member
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Dec 8, 2004
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87
hey all ,I got one for you that hopefully someone can help with.
My complete restoration is almost complete, only needs tires and back bumper. Bronco has been running for a year and have not had a problem with fuel pressure (running at 5psi on gauge at regulator.) The engine is built a bit, edelbrock performer manifold and edelbrock 650 carb, pertronix high performance ignition and an rv cam. Engine was running at about 200 degrees, Thermostat is working great (190) everything was working fine until recently. It now climbs up to 230 and when it gets this hot my fuel pressure drops to zero. Bronco still runs though. I have braided Stainless steel lines from manual fuel pump to regulator and then to carb. if I Shut it off it doesn't want to start, it will with some throttle, just sputters and coughs. I am assuming I am really close to vapor locking. here is the rest of the story. The outside temp here lately has been above 100, got to 109 the other day. so my couple questions are, First can the ambient air temp make that much of a difference, if so what can I do to help cool this (other than not drive it when it is over 90degrees) Oh ya brand new three core aluminum radiator. any ideas? next question is about putting an electric fuel pump on it but I have dual tanks. I have been reading about solutions and one is to install an electric fuel pump back at the tank. So do I just extend the line from my aux tank to that location? Will the electric fuel pump pull fuel from the aux tank if I extend the line? is putting an electric fuel pump a solution to the fuel problem? I know the fuel problem is a result of the heating problem, but honestly I am not sure what I can do about the heating problem. Any advice would be appreciated. Thanks Jerry
 

Rustytruck

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Feb 24, 2002
Messages
10,830
more than likely it the alchol in the fuer. might try to find pure gas if available in your area. other wise run it a far as you can and when it stops get under the truck and see if you can hold onto the fuel line with your hand. if you cant its probably over 150 F .
 
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brncofinatic

brncofinatic

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ya already done that and I cant hold onto it at least the line up by the engine, same with the fuel pump to hot to grab, you can touch them but you pull your hand away. Just took it out, drove 6 miles held right at 200 on temp gauge but it is only 80 degrees out right now, but my fuel pressure was 4.5 when I started it and it was down to 2 when i pulled it back into the shop. Suppose some premium gas, non ethanol would help?
 
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brncofinatic

brncofinatic

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pics of the fuel line. It is tight to the engine, suppose it is picking up to much heat from the engine?
 

Oldtimer

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Feb 4, 2005
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Santa Clara Co, CA
Just spit balling here...
Engine at 230* now, was 200*
Is low fuel pressure causing engine to run lean, and get hotter?
How old is mechanical fuel pump?
 

TX-ZACH

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Sep 27, 2021
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149
I am having some heat related issue with fuel right now and going to try a phenolic spacer to the carb. They are cheap and an easy task, I just gotta be sure I order the correct part.
 
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brncofinatic

brncofinatic

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thanks for the ideas, so the mechanical fuel pump is old, (20years) about the only thing original, so i thought about replacing it, but it works when it is cool so kind of went away from that idea. The running lean from the fuel is something I also considered and yes that could be the cause, and that is where I went to the electronic fuel pump in the back and get it away from the heat. I also looked into the phenolic spacer for the carb, but I think the problem is happening before the carb, the heat in the carb could be exasperating the problem though. I could try and cover the lines but I worked really hard to get those braided stainless steel lines and I hate to have to cover them. I am going to take it to town and fill it with premium non ethanol and see if that makes a difference.
 
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brncofinatic

brncofinatic

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all,
went to town yesterday filled it with premium non ethanol and ran it through the towns street lights, stop and go stayed right at 190 and fuel pressure reduced but didn't get to 0. Came home and it never ran over 200. Temp outside was about 80. I think the fuel helped, but I think the fix is to reroute my fuel lines. thanks for all the advise. Jerry
 

pcf_mark

Bronco Guru
Joined
Jun 11, 2010
Messages
3,424
Couple of things - the picture really helps.

1) Carb spacer is good suggestion especially for a Carter style carb like you have. A shield is even better you just have to trim them to fit sometimes.
https://www.edelbrock.com/heat-insulator-gasket-for-divided-4150-square-bore-0-320-thick-9266.html
2) You have an incredible number of linear feet of flex hose - 6' is my guess Every inch of that is being exposed to engine heat on its way over to the regulator and then over the carb. When the regulator reduces the pressure the boiling point comes DOWN so that length of hose is more likely to vaporize. I would reduce that to as little as possible and use metal tube with an insulating sleeve on anything left. On my EFI conversion I send the fuel from driver to passenger side in the rear far away from the heat then the line runs up to the fuel rail fitting on the passenger side. Absolute minimum amount of lines in the engine compartment.
3) Why do you have a regulator? A stock mechanical pump is not going to drown the Edelbrock carb. Less parts, less lines, less pressure change.
 
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brncofinatic

brncofinatic

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Thanks for the advise, I only put the regulator on because of the warnings on the edelbrock carb, and was told the old mechanical pumps can generate as much as 10psi so I put it on. That is when the line got stretch tight across the front of the engine. I do think you are right, I need to move the line but was thinking just pulling it up off the engine and run behind the distributor would reduce the heat exposure, maybe not enough though. Is a stainless steel tube better than the braided line if I am running a long distance?
 

DirtDonk

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Nov 3, 2003
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The good news is it’s getting plenty of cooling air from the fan.
Whether that’s good enough or not I’m not sure.

A lot of extra line there for sure. But it’s certainly hard to plumb things cleanly in any bronco engine compartment.
Is there any way you could move it over to the driver side and shorten the runs and still take advantage of the cooling air?
The wheel wells are relatively cool because of the airflow and lack of heat on the other side, and that’s where Ford chose to mount the heat sensitive ignition modules.
Proving that it’s at least one cool area under the hood.
 

pcf_mark

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Jun 11, 2010
Messages
3,424
As a cheap and easy test go to HomeDepot or Lowes and get some foam pipe insulation and wrap the lines from the pump to the reg and over to the carb and just wire tie it in place. That will reduce the temp and give you a margin when sitting in traffic or after you shut the engine off. If it helps then you can re-plumb the line knowing it will help. $1.99 for 6' is pretty cheap test!

https://www.homedepot.com/p/Everbilt-1-2-in-x-6-ft-Foam-Pipe-Insulation-ORP05812/204760811
 
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brncofinatic

brncofinatic

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great idea to test it, I have some of the pipe insulation. it is supposed to be 105 today, I will try it this afternoon. Thanks a very cheap test to check it. Appreciate the advice from all of you!
 

gnpenning

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I have more questions than answers.
You now know that you aren't over pressuring your carb from your pressure readings, no need for the regulator at this point.

Having the line laying on the thermostat housing is a issue along with all that area to pick up heat. Pfc suggestion about the foam is a good one, along with his thoughts on excess fuel line.

How close to the fuel lines is your exhaust going back to the tanks?

Are you running stock lines in stock location going back to the tank?

Look at your fuel system from tanks to carb. The whole system needs to be correct and away from heat as much as possible, especially with ethanol.
 
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brncofinatic

brncofinatic

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The lines are isolated from the exhaust. I used the stock setup from tank to selector and then ran new line on the exterior of the frame up to the fuel pump, just so i could isolate from the header heat. I do agree with you, I do not need the regulator now that I know the pump isn't over pressurizing so that is my plan, remove the regulator and extra line and put the line from the pump directly to the carb. Doing that allows me to pull it off the engine and the thermo housing. I think that will help alot. Been working late every night so I haven't have time to test with the insolation but will this weekend. Thanks for the input. appreciate it. Jerry
 
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brncofinatic

brncofinatic

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Just following up, I removed the regulator and line from reg to carb and rerouted the fuel line so it no longer sits right on the engine. Ran it yesterday afternoon, 85-90 outside and had no problems. I think I had multiple problems all adding up to overheating. I think by rerouting the fuel line, the fuel is no longer heating making the engine run lean, overheating in hot temps. I think it is fixed, next week is supposed to be 100 + so it will get tested. Thanks everyone for your input!
 
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