Date:         Wed, 3 Aug 2016 18:39:03 +0000
Reply-To:     Richard Koerner <rjkinpb@SBCGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Richard Koerner <rjkinpb@SBCGLOBAL.NET>
Subject:      Bucking/Loss of power on HOT days
In-Reply-To:  <CA+az7_5SkjieYj0gPUhu13GDTecond1A_EuxrMUmVwZ7aLY36A@mail.gmail.com>
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Am having bucking and loss of power on very hot days.
My van is an 85 2WD (233,000 miles), manual tranny, with a 2.2 Subie engine (recent conversion by California Westys in San Diego), engine was completely rebuilt, now about 13,000 miles).
The symptoms are classic "vapor lock"; yes, unusual with pressurized fuel delivery on fuel injected engines, but I've been going through the List Archives and there have been cases resembling vapor lock.
Typically, everything runs fine at freeway speeds in hot conditions; the bucking problems start when I pull off freeway and have to contend with stoplights and idling and low speed.

This has happened at low elevations but hot (Florida and Laughlin, Nevada) and also at high elevations (Gunnison, Colorado) on a warm summer day.  Problem disappears when van is allowed to cool overnight; starts fine and runs fine the next day.....until it gets hot outside and van is moving slow.

Mild whining (not screaming) from fuel pump when this happens.  I suspect some cavitation and pump damage occurred.  Anyway, I've replaced fuel pump twice (first time with GoWesty cheaper one and second time with GoWesty Bosch expensive one).  And I've replaced the round gray fuel filter 4 times.
So the bucking/loss of power happened again 2 days ago as I drove through Las Vegas in middle of the day; everything was fine until I pulled off the freeway to a Walmart; apparently at low speeds things really start heating up.  My temperature gauge never got higher than 1/2, normally it's at about 1/3 (completely new radiator, hoses, pipes with the Subie conversion).
My biggest suspicion is debris clogging outlet of fuel tank; maybe debris from 30 years got loosened and stirred up when fuel tank was lowered to replace plastic coolant lines with stainless steel lines?  Fuel pump is straining to get fuel perhaps causing cavitation and diminished liquid fuel supply to filter and motor?

Other things I've read about include:  gas cap, charcoal cannister, bad coil, fuel pressure regulator, bad ignition coil.
Whatever it is, I most definitely think it related to HOT ambient temperatures.
Any words of wisdom?  (I'm also going to cross-post this query to the SubaruVanagon List.)

Rich
San Diego