I was up in the mountains this weekend and it is the first time I've been up there with a fuel pressure guage. Fuel pressure is about 16-17psi at idle here at home which is basically sea level.

When I fired my truck up Sunday morning at 5,600ft I had 12-13psi at idle. As I dropped back into the valley and lost elevation I watched my pressure creep back up.

Why does this happen? I know air gets thinner and gravity changes as elevation increases, but I've never heard of liquid being effected by elevation.

Does this mean you are more susceptable to VP44 problems if you live in higher elevation? I managed to suck my pressure all the way down to 6psi as I left the cabin and the boat hooked to me.

 

Hmmm... maybe you should get some stacks.




I've had mine up that high and back to sea level and never really noticed a difference. Are you running an electric or mechanical gauge?

 

Now that's interesting...how low could you get your FP down at a lower elevation??

I wouldn't think that elevation would change the FP at all, the thin air really shouldn't affect that but I could be wrong.



~Nick

 

Yeah, weird. Normally I can't even suck my fuel pressure below 10psi at WOT at sea level. Which, would be about right for a 4psi difference at 5,600ft.

Sea level 17psi idle/ 10psi WOT

elevation: 13psi/6psi

I have an electric guage, I have the Juice/Attitude combo.

 

My fuel pressure isn't as high when the fuel is cold...was it cold where you were?

 

You know what, this thread isn't about stacks, but it is about the hottest topic for us 24v guys.

RJF, how you doin man, took you a while to join this site comin from towrig.

 

Hey is this were we talk about stacks?? Yeah, that is weird with the fuel pressure though? Must be some kind of scientific explanation. At sea level it's like 14.7 or something right, higher up it would be lower? I don't think the thin air would do it, I guess it would have to do with the atmospheric pressure? Higher/lower but would it affect it that much? I don't know....

 

scientific explanation _

You have an air bubble or small leak in your fuel pressure line, and as the density of the outside air changes, so does it.



or Maybe.......

The fuel pressure gage you are using compares fuel pressure to the outside air pressure somehow. As the outside air pressure goes up the difference between the fuel pressure and the outside air pressure gets smaller, therefore you gage reads lower...and vice versa



but I am no scientist, cuz I think both of these reasons will make it do the opposite of what it is doing

 

whats "good" pressure for a sorta stock truck? right now iam at 11psi idelin and running hard with 2k in the bed i am down around 6ish pulled it little past it on the way back empty and once i let out of it she clum right up I am heading out this weekend with the horse cart n one horse pulling the mountains Ill see what she does then but I already thinking I need a new lift pump.

 

Correct. Most FP guages (the mechanical type) use Bourdon tubes to measure fuel pressure. They are unfortunately affected by variations in atmospheric pressure.

http://www.efunda.com/designstandard...rdon_intro.cfm

http://www.tpub.com/machines/9c.htm

 

With this head cold all I keep seeing is Bourbon guage..... Not to early to drink if it's for medical reasons right!!

 

But your second guess is right.... must have stayed at a Holiday Inn Express last night?

 

HaHa RJ...funny you mention that. The night I left you're place we stayed in a Holiday Inn Express...and the next morning we felt so smart we changed to the Scotty II in the parking lot. Pretty scientific, don't ya think??

Chris

 

...and cut the cowl hole with your pocket knife... huh?