Fuel Line material and routing - Page 2 - Vintage Mustang Forums
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post #16 of 29 (permalink) Old 09-18-2018, 03:30 PM
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Originally Posted by PA_cob View Post
That works great but I still have vapor lock issues mostly after the car has heat soaked for awhile after driving it.
If I'm reading this correctly, you're saying that you have vapor lock issues after you have parked the car, and it heat soaks thus causing your problem? Do I have this correct?



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post #17 of 29 (permalink) Old 09-18-2018, 05:08 PM
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The way a fuel pump helps prevent vapor lock is with a return circuit, typically. EFI almost completely eliminates these issues by bumping up the pressure to increase the boiling point as well as adding a return like to help keep fuel cooler. I don't see how an electric, single line pump can solve any issues over a mechanical pump?

I'm running braided teflon AN line from the pump to the carb with the Heatshield Hot Rod Sleeve (https://www.amazon.com/Heatshield-Pr...tection+sleeve) along with a phenolic spacer. I'm really hoping this will be adequate, as I've the fuel line ran behind the p/s pump and then by the compressor and finally along the valve cover to keep it clean.

If this isn't enough, then I'll likely put some of DEI's Vapor Block sleeve around it to further reject heat: Vapor Block? Fuel Line Sleeve | Design Engineering Inc
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post #18 of 29 (permalink) Old 09-18-2018, 05:43 PM
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PA..please accept my apology if I offend. Could it be something else? A bad coil will get hot and quit for a bit. Sometimes the old gas tanks aren't vented and the pump pulls all it can till cap is loosened to allow venting. Seems like you have done a lot of good things. Good luck and trying to help.
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post #19 of 29 (permalink) Old 09-18-2018, 06:03 PM
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Originally Posted by wannabridin View Post
The way a fuel pump helps prevent vapor lock is with a return circuit, typically. EFI almost completely eliminates these issues by bumping up the pressure to increase the boiling point as well as adding a return like to help keep fuel cooler. I don't see how an electric, single line pump can solve any issues over a mechanical pump?
You're right about EFI but an electric pump back by the tank can help too; a mechanical pump has to pull fuel all the way up the line from the tank, so that's 10-12 feet of fuel under negative pressure (makes it easier to boil). Did a bunch of research on this since over the summer since my car would reliably vapor lock if I was in traffic on a hot day for 20+ minutes (NYC area). Putting an electric pump at the back to push fuel up to the mechanical totally fixed the problem.


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post #20 of 29 (permalink) Old 09-18-2018, 06:09 PM
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@PA_cob lots of good advice here already, I'll just add from my own experience that especially if you spend time in hot weather keeping everything away from hot engine surfaces is key. Also I don't see an inline filter before the carb and you should have one to keep it clean. If you want to be extra sure to avoid vapor lock, I recommend a plastic filter rather than metal, though you have to be sure to change it regularly since the plastic degrades (probably every 6 months - 1 year). Good luck!


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post #21 of 29 (permalink) Old 09-18-2018, 06:15 PM Thread Starter
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Quote:
Originally Posted by PA_cob View Post
That works great but I still have vapor lock issues mostly after the car has heat soaked for awhile after driving it.
If I'm reading this correctly, you're saying that you have vapor lock issues after you have parked the car, and it heat soaks thus causing your problem? Do I have this correct?
Exactly right. It's super hard to start and runs a little rough for a little bit until the temp starts to come back down.
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post #22 of 29 (permalink) Old 09-18-2018, 06:19 PM
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OP, something to try.... drive, shut off, heat soak as usual, pull air cleaner with engine still shut down, operate throttle and check for pump shot. If exists, repeat two or three times for consistency.

Unfortunately, Demon's don't appear to have fuel level windows and the carb must be removed and upended to remove the cover. I usually check my 4100 by pulling the top cover off. Easy to see what fuel is in there. Holleys have the windows.

If no fuel exists in the carb, it's boiling out from the heat soak.

It sounds like you're losing fuel supply when shut down and it won't re-engage. An inline fuel pressure gauge might lend some clues.

IMO, do a thorough diagnosis before making any more changes. In the past, if I'm thinking the carb is involved, I'll even swap in a known good carb for comparison. You'll find the problem eventually.

FWIW I ran the race car for decades with a Holley blue pump, aluminum fuel line and a short braided to the engine with the only insulation in the header area to protect the hosing (vastly different routing from OEM). Never a lick of trouble. With that anyway

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post #23 of 29 (permalink) Old 09-18-2018, 06:23 PM Thread Starter
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Thanks for all the info guys. I changed out my fuel line today mostly solid with a few inches on either end. Had to take it up to shop get a tire fixed. So don't have a pic yet. I thought it might be cool but tried a different one and the result was the same. The engine never gets hotter than about 210 at idle now since I worked over the cooling system and usually runs about 190. Those temps are within normal operating range. I'm hoping that the new line fixes this issue. But I have been noticing another issue as well. When it's warmed up, and I am breaking the engine acts like it wants to die just for a second and the rpms dip below 500 and then jump back up to 750. I think this may be a float level issue. If that's the case could that also be contributing to the hot start and idle issues?
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post #24 of 29 (permalink) Old 09-18-2018, 06:33 PM
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Try cold start and braking similarly before engine warms. If no problems, it's not a static float issue.

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post #25 of 29 (permalink) Old 09-18-2018, 06:34 PM Thread Starter
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I don't notice it when it's cold. Engine slightly warmed up runs really nice no issues. It's once it's at normal operating temp that I see it. And if it gets hotter than that say like 210 it really gets bad.
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post #26 of 29 (permalink) Old 09-19-2018, 10:19 AM Thread Starter
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So I tested out the engine dying while braking issue this morning with a cold start. No attempts to die whatsoever. RPMs stay right at 750. Definitely a hot engine issue.
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post #27 of 29 (permalink) Old 09-19-2018, 06:01 PM
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Originally Posted by Ojenkins View Post
You're right about EFI but an electric pump back by the tank can help too; a mechanical pump has to pull fuel all the way up the line from the tank, so that's 10-12 feet of fuel under negative pressure (makes it easier to boil). Did a bunch of research on this since over the summer since my car would reliably vapor lock if I was in traffic on a hot day for 20+ minutes (NYC area). Putting an electric pump at the back to push fuel up to the mechanical totally fixed the problem.
The pressure drop in the line from the pump is going to likely be negligible, but it might just be enough to alter the boiling point... I never had an issue with a stock pump driving in TX heat as a kid (100+ for months at a time, sitting in traffic w/ a/c and no idle compensation).

It seems to me that it's a small combination of multiple factors that add up to tip the scales in favor of boiling vs not. I'd personally start with the cheapest/easiest options - hose re-routing, adding/changing insulating spacer and a proper hose wrap before going through the trouble of doing a proper electric pump (you really need to install an inertia switch if you do an electric pump, like the one from Revolution Electronics).
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post #28 of 29 (permalink) Old 11-12-2018, 06:30 PM
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I used AN fittings and AN stainless braid from the apron to the F/P then the same to the carb.
You do the same from the apron to the carb. if that's the route you want to take.
]
What are you using for connection at the F/P? I just got the AN stainless braid and Iím wondering the best connection to the pump (using a Carter fuel pump).

Also, any vapor lock/temp issues with that setup? Always wonder how the braided stainless works vs traditional steel in that capacity.
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post #29 of 29 (permalink) Old 11-12-2018, 09:21 PM
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A/N fittings used through out with no vapour lock issues.

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