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Date:         Wed, 3 Aug 2016 20:05:12 -0400
Reply-To:     Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject:      Re: Bucking/Loss of power on HOT days
Comments: To: Richard Koerner <rjkinpb@SBCGLOBAL.NET>
In-Reply-To:  <386968489.11490288.1470264618749.JavaMail.yahoo@mail.yahoo.com>
Content-Type: text/plain; charset="UTF-8"

Your welcome. BTW I'm currently on a business trip in Modesto CA. It is hot here during the day!

Dennis

-----Original Message----- From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Richard Koerner Sent: Wednesday, August 3, 2016 6:50 PM To: vanagon@GERRY.VANAGON.COM Subject: Re: Bucking/Loss of power on HOT days

Wow Dennis, thanks so much for your information! Your description of how things are working regarding this Bucking issue makes complete sense. I was having trouble figuring out why my van would fail late at the end of a hot day but then magically fix itself overnight; but starting out with a tankful of cool gasoline in the morning made it easy on the fuel pump, whereas after an all day drive in hot weather would leave me with a tank of hot gasoline with the vapor pressure changing in the undesired direction.

OK....here's what I'm going to do: New fuel tank with a 12 mm outlet (instead of the current 7 mm outlet....almost triple the cross-sectional area for better flow). New charcoal filter valve (mine might be good but since 31 years old and only $40 seems worth it for the peace of mind anyway). I got these on order from Van-Cafe. Also ordered a German Bosch fuel pump (one of the few remaining) and fuel filter from Bus Depot....will keep the current Bosch fuel pump as a spare. I went over to my mechanic and discussed the plan; he is in complete agreement; he mentioned that just 2 weeks ago another customer had the exact same situation. So it's going to cost me a few bucks, but so worth it to have renewed confidence in my vehicle. Roadside problems are costly in both time and money and frustration. Thanks again for your help. Rich San Diego

From: Dennis Haynes <d23haynes57@hotmail.com> To: 'Richard Koerner' <rjkinpb@SBCGLOBAL.NET>; vanagon@GERRY.VANAGON.COM Sent: Wednesday, August 3, 2016 11:55 AM Subject: RE: Bucking/Loss of power on HOT days The change in fuel pump noise is a key. As the fuel recirculates through the system it will pick up some heat from the engine and transfer it to the tank. This temperature increase will raise the vapor pressure in the fuel tank and any restriction at all will make the fuel vaporize in the pump. If you have the original tank you are also plagued with the smaller tank outlet.

Make sure all the fuel lines in the engine are somewhat insulated from picking up engine heat. Another possibility if this is happening after a highway run is that the tank isn't being vented. Most of the engine conversions I have seen do provide for operation of the vapor control valve. This valve was opened by engine vacuum as the throttle was opened. The valve is located near the air filter. During high fuel consumption periods not having the tank vented could put it into a vacuum situation. I have seen tanks get collapsed by failure here.

Dennis

-----Original Message----- From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Richard Koerner Sent: Wednesday, August 3, 2016 2:39 PM To: vanagon@GERRY.VANAGON.COM Subject: Bucking/Loss of power on HOT days

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


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