Date: Mon, 17 Aug 2009 14:13:48 -0700
Reply-To: Rocket J Squirrel <camping.elliott@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Rocket J Squirrel <camping.elliott@GMAIL.COM>
Subject: Re: Not quite a backfire . . .
In-Reply-To: <013a01ca1f7d$fefc6f90$6501a8c0@PROSPERITY>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Gee -- that /does/ sound like fun!
I am under the possibly mistaken impression that there is such a thing
called a backfire that is so explosive that it can damage exhaust
components -- like blow off a muffler or something. And that these mild
coughs I heard when one cylinder's worth of fuel popped mildly a few times
in the exhaust manifold is called something else?
Thus the title of this thread . . .
--
Mike "Rocket J Squirrel" Elliott
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
Bend, OR
KG6RCR
On 8/17/2009 2:02 PM Scott Daniel - Turbovans wrote:
> 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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