VAPOR LOCK

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   Vapor lock was around long before they started adding ethanol.  That only aggrivated the issue. Car makers finally started addressing it in the 70's when they added return lines. GM put a return line at the pump and AMC used a fuel filter with a return line. 

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Heavy 488 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Apr/27/2019 Location: In the Status: Offline Points: 3553	Post Options Post Reply Quote Heavy 488 Report Post Thanks(0) Quote Reply Posted: Apr/30/2022 at 2:15pm
	Vapor lock was around long before they started adding ethanol. That only aggrivated the issue. Car makers finally started addressing it in the 70's when they added return lines. GM put a return line at the pump and AMC used a fuel filter with a return line.

Scrappy Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: Jun/26/2019 Location: Alpharetta, GA Status: Offline Points: 255	Post Options Post Reply Quote Scrappy Report Post Thanks(1) Quote Reply Posted: May/02/2022 at 11:35am
	The best way to find non-ethanol fuel is to use this site: https://www.pure-gas.org/. You can find the locations by text list, map, or KML file (that you can open with many nav apps). My vapor lock experiences are not with AMCs, but the principles and fixes are the same. This is what I did for my '57 Chevy, which is still carbed (but will soon be F.I.), most of which require modifications and/or parts you might not have on your car (e.g. electric radiator fan): A) Run non-ethanol gas. B) Phenolic insulator between manifold and carb. C) Use a temperature switch and relay powered "hot" at all times to let the radiator fan run after stop until it drops to a particular point. Obviously, this doesn't help when running to keep vapor lock out of the line from the tank, but it made re-starts much easier. Some folks refused to believe this made a difference, so I did two tests on two days back-to-back at nearly the same conditions (see the pic below). Please no quibbling that the start temperatures are not exactly the same -- the point is the trend. D) Created a return line. 0.035" orifice from McMaster-Carr and an AN-3 bleed line back to the tank. E) Moved the fuel pump to inside the tank. In terms of effectiveness (from most to least) during running, I'd say it was: D, E, B. For fixing the hot-start issues: C, E, A. Edited by Scrappy - May/02/2022 at 11:38am

PHAT69AMX Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5919	Post Options Post Reply Quote PHAT69AMX Report Post Thanks(0) Quote Reply Posted: May/06/2022 at 3:01pm
	oldguy - might the magic words here be: "... just replaced the fuel pump"...
	Link to a Short YouTube Burnout Video

Cloudyday Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Nov/27/2020 Location: Southern Indian Status: Offline Points: 68	Post Options Post Reply Quote Cloudyday Report Post Thanks(0) Quote Reply Posted: May/27/2022 at 6:01pm
	I just did both, replaced my Carter fuel pump that had all of 200 miles on it before it crapped out and installed a 3/8ths inch thick gasket between the aluminum intake and carb. Much better warm starts and smoother idle.

oldguy Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Nov/07/2011 Status: Offline Points: 94	Post Options Post Reply Quote oldguy Report Post Thanks(0) Quote Reply Posted: May/27/2022 at 6:36pm
	I put an electric pump in the trunk and the problem is gone