[T3] Fuel pressure and elevation

[d.nohejl at gmail.com (Daniel Nohejl)]

Ok, so I read around a little more??only on some other automotive forums, so I don?t have anything scientific, but it seems that unless one has an ?absolute gauge" then for every 1000? of elevation gain your average fuel pressure gauge reads anywhere from .5psi-1psi lower than actual fuel pressure. This makes sense since at sea level, my gauge read 29psi but at around 8000? it read 25psi. So what I wound up doing at elevation was increase the fuel pressure by 4 psi because the gauge reading was off??assuming that what I read about gauges and altitude is true.

Here?s another possibility??.I also had a clogged fuel filter which ultimately caused a really horrible and constant moaning sound up at the fuel damper/dampener. At the stage of the trip where I measured the fuel pressure, the noise at the damper was only intermittent and I hadn?t yet identified the filter as the culprit. Perhaps the pressure reading was low on account of the clogged filter and I raised it to normal which then became too high once I changed the filter.  

Jim?s the physicist, though, so maybe he can give us the straight dope on fuel pressure and altitude. 

Incidentally??.am I the only one who sometimes doesn?t receive responses to posts? I only saw Keith?s response to me by going to vwtype3.org <http://vwtype3.org/> and looking at the archive for August. Sometimes it happens with replies to me and sometimes in relation to others. For example, I might receive someone?s reply to a post without ever receiving the original post in my inbox. 
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