Vaporlock and external electric fuel pump - Vintage Mustang Forums
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post #1 of 11 (permalink) Old 05-13-2019, 10:31 AM Thread Starter
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Vaporlock and external electric fuel pump

I've made a ton of progress getting my 289 running properly. I thought I fixed my vaporlock issue but on a hotter day it did it to me again. Then I replaced the entire fuel system: new sending unit, 3/8 lines, clear filter, summit racing pump, insulated pump to carb line, carb fuel line with a gauge port and a phenolic resin carb spacer. Then I got some ethanol free 93 fuel and put in a half tank. STILL the engine died on me during a light drive. I pulled over and unscrewed the plug for the fuel pressure gauge and it hissed several times. Took me 3 hours to get it running again.


I've noticed the secondary fuel bowl is never filling. Maybe its closed and keeping an air bubble in the fuel line running up to it, then when hot expands into the primary line. I will adjust it next time I work on it.


I've wondered if my old fuel cap could have something to do with it. Doesn't hiss when I remove it. When the car finally did run again, I had taken off the air filter and left the gas cap open. Anyway I got so frustrated with it this time around, I don't want to look at the car for a few days.


Possibility I actually just ran low on fuel and sucked air. My fuel filter had a bubble in it when it stalled. If so, that means this thing sucks down gas FAST.


ELECTRIC PUMP
I plan to put in a helper pump but now that all of my fuel lines are 3/8 I'm realizing that all the 7 PSI external pumps are 5/16. Wondering what I should do here...
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post #2 of 11 (permalink) Old 05-23-2019, 11:53 AM
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Are you sure the pump is continuing to run? It sounds like the pump may be getting hot, overheating, and once its had time to cool you can go until it overheats. Iíve been down this road, I didnít realize at first the pump was shutting down.

A return line using a return pressure regulator and fuel log (the line at the carb connecting to both fuel bowls) designed for the return line could be one solution. Allowing the pump to circulate fuel helps keep the pump cool. Barry Grant used to have this information and design options on his web site, not sure if Barry Grant is still in business but you might search for it.

Youíve done a number of good things, but given the bowl is dry Iím rather confident that your pump is overheating. Air simply canít keep fuel from flowing in, it may displace some fuel as it flows, but an electric pump is going to fill the bowl especially if itís allowed to run a few seconds after the motor stalls. Boiling fuel and vapor lock on a mechanical pump design are a different animal when you convert to an electric pump.

Also, your cap should vent the tank, youíd never want to obstruct venting the tank since that too would cause a vacuum for the pump to work against. Things have changed with modern cars and the fuel system design has changed such that there are better controls for allowing air to displace fuel, but your design needs air and thus there will never be a hiss.

Good luck with it, Iíll poke around too and see if I can find the Barry Grant return line info.
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post #3 of 11 (permalink) Old 05-23-2019, 12:02 PM
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This design is something like what youíd do, obviously the 10AN is not necessary but the fuel flow is something that would let your pump circulate fuel, run cooler, and live longer.

https://images.app.goo.gl/TkPsXr8EwEgqAEGo7

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post #4 of 11 (permalink) Old 05-23-2019, 12:56 PM
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Back in the 70ís when the engines were running much hotter due to emission controls to help prevent vapor lock the fuel pump had a return line to circulate the fuel back to the tank were it was much cooler. Now the carb didnít have that hot fuel boiling off.

Tom

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post #5 of 11 (permalink) Old 05-23-2019, 04:04 PM
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Recirculating the fuel helps when you are running but if you make a mad dash down the highway for 30 or 40 miles then pull over and stop the E in the carb's fuel bowl/s will boil out and back pressure your system so your back to the same problem.



Ethanol boils at 174 farenheit at normal atmospheric pressure. Ethanol blended gas boils a bit higher but still not really great. You have to cool off the carb somehow or other. Running the fuel at a cooler temperature does help.


I wound up eliminating my hard line from the fuel pump location and running a stainless braided line. I re-routed it off any hot engine parts. Wrapped it in thermotec or somebody's heat wrap insulation. Put that inside a black wiring loom. Installed a phenolic carb spacer. I'm close to ethanol boil out in the hottest months but just under now.


I was prepared to go to this step if all else failed;




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post #6 of 11 (permalink) Old 05-23-2019, 05:04 PM
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Make sure your fuel pump is a 12 V and not a 24 V. A buddy of mine had intermittent problems that he thought was a vapor lock, just as you describe. After getting very frustrated he removed the fuel pump, only to find out it was a 24 V. He installed a 12 V and the problem went away. He surmised the pump would operate for a time (that varied with ambient temperature) and then would stop pumping completely, when it got too hot- from not being able to get enough current to operate any longer
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post #7 of 11 (permalink) Old 05-23-2019, 08:51 PM
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My late father in law had a 1968 Cougar GTE 428. He had the same problem. Finally, and this will sound silly, he clamped wooden clothes pins along the fuel line leading up to the carb. They acted as a heat sink and cured the vapor lock.
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post #8 of 11 (permalink) Old 05-23-2019, 09:40 PM
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Originally Posted by macstang View Post
Recirculating the fuel helps when you are running but if you make a mad dash down the highway for 30 or 40 miles then pull over and stop the E in the carb's fuel bowl/s will boil out and back pressure your system so your back to the same problem.



Ethanol boils at 174 farenheit at normal atmospheric pressure. Ethanol blended gas boils a bit higher but still not really great. You have to cool off the carb somehow or other. Running the fuel at a cooler temperature does help.


I wound up eliminating my hard line from the fuel pump location and running a stainless braided line. I re-routed it off any hot engine parts. Wrapped it in thermotec or somebody's heat wrap insulation. Put that inside a black wiring loom. Installed a phenolic carb spacer. I'm close to ethanol boil out in the hottest months but just under now.


I was prepared to go to this step if all else failed;


I use those Holley isolators and they work. You may have to trim the aluminum plate to fit your application

John

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post #9 of 11 (permalink) Old 05-23-2019, 09:57 PM
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+1 for adding a return line to cope with modern fuel blends.

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post #10 of 11 (permalink) Old 05-23-2019, 10:02 PM
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Well...let me suggest:
1. Fuel line insulation... I wouldn't. Insulation keeps heat INSIDE and allows it to build up. Better to use some sort of heat sink. In the "old days" we used to attach metal binder clips to the steel line. I'd probably get some of the LED heat sinks shown below, drill the centers out to a slight interference fit on your steel line and install with some heat sink glue.

2. Clear Filter? You mean the "Fire Starter" version? Your filter should be between the pump and carb, and I recommend steel/brass in-line attachment with NO rubber hose.

3. Make sure you don't have any place in the line from tank to pump where there is the possibility of the system "sucking air" due to a loose or poorly made connection or defect.

4. Make sure there are no restrictions in the system, the "sock" is in place, and the fuel cap vent is allowing outside air to enter the tank to replace the volume of fuel used.


LED Heat Sink, 29mm OD, 6mm ID.


For some reason I can't see the image so here is the link: http://minaluminum.com/Clkj_Images/u...1642747097.jpg

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post #11 of 11 (permalink) Old 06-11-2019, 12:32 PM Thread Starter
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So I solved the problem a while back, I just didn't make my way back to the forum.


I installed a Holley 12V pump near the tank and thought I was good. It seemed to work and then the car stalled AGAIN if I gave it too much gas or went uphill. I went ahead and removed the primary bowl and soaked everything in carb cleaner and rebuilt it. Hasn't stalled since. The sintered brass filter at the inlet to the bowl had clogged I think. The shop that first got the car running a few years back didn't bother to use a fuel filter and they also let the car sit a lot. I think I've said enough...

As for the secondary bowl: it was over-adjusted.

I also bumped up my jets one size to see what would happen--I think it was running pretty lean before. Now it idles perfectly and never stalls on drives. It just seems to hesitate at takeoff. One or two seconds after takeoff the power seems to dip one time. I know I read about that somewhere but I've researched so much stuff lately I can't recall. It also seems low on power, I can't spin the tires and it feels sluggish. I do need to make some throttle linkage adjustments and install my aftermarket kickdown rod, and also get the transmission looked at (leaking).


Thanks for all the input.
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