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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