Date: Mon, 17 Aug 2009 14:02:09 -0700
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Not quite a backfire . . .
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I did read that part, but I get it now,
the theory is that a plug fouled and when the fuel came back on, the plug
couldn't fire it, so the fuel went into the exhaust and caused backfires
there.
I just didn't catch that quite the first time.
It makes sense of course.
speaking of oil fouling, and 1.9 engines, if that's what you have. I was
just checking compression on an 84 1.9 that overheated,
and I found 120 psi on the forward two cylinders, and 148 on the aft two.
The left head is fresh, so the valves should be good there.
When I put oil into the low compression cylinder on the left side,
compression shot up to 190 .......which I expected a little......indicating
that rings/pistons are tired in the two forward cylinder, or at least in
that one. . ( your oil comment is what started me here ) .
I know the engine ran for a while quite low on coolant. I'm wondering if
those two forward cylinders didn't get much coolant at all, and the rears
got enough to not suffer cylinder damage . Just a theory. Left head coming
off today - water gasket there blown out on top. Might be putting in new
pistons and barrels.
what fun !
Scott
----- Original Message -----
From: "Rocket J Squirrel" <camping.elliott@gmail.com>
To: "Scott Daniel - Turbovans" <scottdaniel@turbovans.com>
Cc: <vanagon@GERRY.VANAGON.COM>
Sent: Monday, August 17, 2009 12:39 PM
Subject: Re: Not quite a backfire . . .
>
>
>
>
> On 8/17/2009 11:36 AM Scott Daniel - Turbovans wrote:
>
>> The coolant temp should not drop to a very low reading during a long
>> descent in the summer.
>
>> I would be thinking about a thermostat not working correctly if I saw
>> that on one of my vans.
>> This is the main thing I wanted to comment on.
>
> With no pressure on the gas pedal, the fuel is totally shut off, so the
> engine is not firing on any cylinders and after about 20 minutes with cool
> air blowing past it, it will lose heat. I first observed this in 2007/2008
> on the long drop down from Laguna Mountain in San Diego county and there
> was quite a lot of to and fro on this matter until the list sorted this
> out as being basically an off engine in cold air being spun by its
> crankshaft. This is the second thermostat, and the behavior is the same.
> It was probably in the low-50's outside, and that's cool enough to suck
> heat out of the engine quickly. The Laguna Mountain descents were in the
> 30's and lasted 20 or 30 minutes. I don't think an engine can stay warm
> with no fuel when driving @ 40 mph and spinning at 2,000 to 3,000 rpm very
> long.
>
> Where does the thermal sensor for the dash gauge sit w/r/t the thermostat?
> engine side or rad side? Gotta be the engine side -- right?
>
>> re
>> With no fuel in the cylinders for so long, a
>>> plug got fouled with oil. Unburned fuel got into the exhaust manifold
>>> and
>>> ignited there, causing the mild explosions we heard.
>>
>> Yes....backfire like sounds can be from fuel in the exhaust system
>> getting ignited.
>> however, by your own logic and indications observed ( 02 meter ) you
>> believe that the throttle switch shut off all fuel to the injectors,
>> so how could there be unburned fuel in the exhaust system, if that were
>> true ?
>>
>
> Ya didn't read my post well enough. When we hit the flat Mrs Squirrel
> pressed lightly on the gas pedal, which would start gas going into the
> intake. Any cylinder with a fouled plug, due to long downhill @ 2,000 to
> 3,000 rpm and no gas, would send that unburned fuel into the exhaust
> manifold. To go "cough" as it popped out there.
>
>> that sure is a special area.
>> They only just opened McKenzie Pass *now* ?? In August ?
>
> It's true -- they were re-paving it and now they are re-striping it.
> I am certain that the re-paving was needed due to a$$holes like that Jack
> Elliott fellow driving inappropriate vehicles over the pass. See
> http://socal2bend.blogspot.com/2008/08/massive-trucks-migrate-to-eugene.html
>
>> on the Eugene ( west ) side of the pass, about a mile or so from the pass
>> itself, on the north side of the road, is a delightful small lake with
>> some campsites around it. Always wanted to camp there once.
>> There is also in that area, another *really* nice little lake, with
>> free unrestricted camping, with campsites around the lake.
>
> Yes sir, I agree. I gotta get me some Forest Service maps pronto -- the
> area is peppered with intriguing places to camp. Right now, being stuck in
> a wheelchair, I gotta stick to more developed places. Which suck, but we
> gotta work with the present conditions.
>
> --
> Mike (aka "Jack" Elliott)
> 84 Westfalia: Mellow Yellow ("The Electrical Banana")
> 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
> Bend, OR
> KG6RCR
>
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