[T3] Fuel pressure and elevation

[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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