fuel pressure guage

[76bonanza]

Those that have a fuel pressure gauge under the hood and mech pump.

How do you read it? Mine bounces between 6-9 then when I shut engine down it holds at 8 for a few minutes the slowly goes down to 0. Is that about right? Around 7 or 8 psi I am guessing?

[rage'nrat638]

Should Be 6.5-8 Tops

[SactoJim]

Usually if I bring mine off idle, it smooths out so I can get a reading......at least until it warms up and then reads 0!...POS!

I'm running an Edelbrock 800 AVS and they say (instructions) not to run over 5.5 - 6 lbs at idle.

[76bonanza]

Jim I got an air filled one and does not 0 out when hot but it bounces alot If I take it off idle it bounces like 6.5-8 so I am guessing around 7 psi.

[76bonanza]

Also jim you have a regulator on yours right? How long after you shut down before you start to lose pressure in line, mine is only a short time is that good? does that mean the pressure is bleeding out the vent in gas cap?

[ghackett1]

My holley mechanical fuel regulator with mechanical pump is set at 5.5 - 6.0 and when it starts thats what it reads. But, after driving it a while it comes down to about 4.5 and stays there. So, I guess all I know is that it is between 4.5 and 6.0! I am running a 600 edelbrock though and they don't like high fuel pressures so I guess I'm okay.

[shifty]

Originally Posted by rage'nrat638

Should Be 6.5-8 Tops

unless you have an LS1....then it would be in the 40-60 PSI range

[SactoJim]

76Bonanza,

Mine holds pressure for a bit too when I shut it down, but not long and I do have a regulator with a return to the tank which would also lend to it bleeding down a little quicker. You must of traded out your liquid filled for the one you got?......almost a "no win" situation. The liquid fill doesn't work right and the other is "jumpy".

Probably the best thing to do (I'm thinkin I might) is put one inside, but if you do it right (using an isolator) it ain't cheap!

[rkarr]

Originally Posted by shifty

unless you have an LS1....then it would be in the 40-60 PSI range

Or a ramjet

[shifty]

Almost forgot - fuel pumps naturally move in cycles, so jumpiness on a non-regulated system would be normal, I think. Example: if I just put power to my pump, the needle on my FP gauge will bounce from 48-54psi as the pump cycles (it's pretty rhythmic). Not sure if this could be what you're seeing. I'm new to electric fuel pumps.

[76bonanza]

That is what I was thinking shifty, that it was the rythem of the pump riding on the cam. And bounces faster but closer the higher the rpm.

So since it bounces between 6-9 I was guessing my psi would be around 7-8.

which would be good with my pump and holley dp.

[76bonanza]

Jim as a side note I found my liquid gauge had a rubber plug in it I drained all the fluid out and reinstalled it, it seems to work the same to me? but no problem when hot. I just am not sure if it will have any bearing on it being acurate or not? The air one I got does not seal good I have to get some teflon tape for it that is what you should use right? Same as plumbers tape?

[SactoJim]

Yes, but only use enough just to cover where threads contact threads. If some of that tape gets into the guage opening it might mess up the reading.

I may have to try draining the liquid out.

[76bonanza]

I hate to drag this up again. Got my air gauge on good. Here is the senerio when truck has been shut down for a while gauge bounces wildly untill warm like 5 minutes of just idling. Then levels out around 6-7 no bouncing. Does it take that long for the lines and tank and all to pressurize then the pump just holds it at that staic pressure?