12 Sec GTA

Schrader valve on fuel rail. 4AN T fitting, goes to 6' 4an line and then to a mech fuel pressure gauge, and then to the fuel solenoid. (yes the "core" has been removed from the valve)

Lately, the fuel pressure gauge which is fed via the 6' line, is starting to "flutter"

at idle, there is a 1/2 - 1psi flicker of the needle.. when I give the car about half throttle, well.. actually anything under WOT, the needle will have about 10 psi of flutter, up and down. It goes from about 49psi - 60. I am set at 50psi on my AFPR.

I'm wondering if this is normal behavior for mech fuel pressure gauges.. or maybe it's the T not flowing enough? It gets worse the harder I drive the car.. But it's not leaning out..

I just want to be safe before I start spraying again (150 shot).

I dont need the fuel noid starving, and leaning out my car. :thumbdn:

maniacc

did you just install a new gauge? if so you might be seeing the injectors pulsing, causing your mechanical gauge to flutter. you can get a special valve that removes line pulses. i think it has 1/8" pipe thread so you could tee in into the line at the schrader valve.

12 Sec GTA

It didn't do it originally... that's why it has me worried.


My pumps are only a few months old.

Walbro 255 in tank, inline t-rex.

and, the flutter at part throttle is BIG.. like 10-15 psi worth... never going below 40 psi though.

12 Sec GTA

Have an idea as to the problem.. I ran out of gas a few weeks ago, and I'm betting air is in the line between the gauge and the test port.. that would cause the fluttering (air bubbles..)

Time to bleed it..

maniacc

Air in the line would do some funny things, or your gauge could be ready to take a big dookie!!!

i would try to bled it first...if you still have a problem then try a new gauge, if you still have a problem, then let me know and i'll send you one of those fuel line dampers. (these dampers were very common on older Caterpillar diesel engines to help remove pulses in the fuel system).

later
larry

87_TA

Not sure of the condion of you motor but if one cylinder is pulling low vacuum then that would probabaly cause some kind of flutter.

12 Sec GTA

or.. maybe a slight vacuum leak in the line.. Never thought about that.. Thanks for the trouble shooting ideas guys.. keep them coming !

Free Bird

iTrader: (1)

I've been having the same prob.
Mine seems to drop though when its under a heavy load. Its the stock pump and I'm running 30# inj.

87_TA

If it drops under load then the pump can't keep up or filter bad.

1989gta

i also have the same problem, i've tried two known good working gauges. I know there are is no air in the line. I don't have a check valve installed in my fuel line, to hold pressure and that may be the problem in my case but are you running a check ball inline?

I ran all new aluminum lines and have a weldon pump/regulator. not using any stock components.

LETHALRACER

I have this problem also. When I get it I pull off the regulator and check for debree in the screen. The other problem is if stuff got in your pressure line. I had silacone in mine some how. Strange stuff can get in your fuel line. Take some pressurized air to it and blow it out realy well. If you are running an isolator than blow out the engine side as well. I have a very small hole on my isolator and it doesn't take much to clog it.

1989gta

mine did this brand new right after install, i have a buddy with the same set up he has a check ball inline but he also has an inlet and out let for each rail mine goes in one and out the other. So that may be another reason.

I do agree junk in your screens can cause a pulse.

B4Ctom1

I found a part of the O-ring that goes on a TPI fuel filter flare fitting (saginaw M16) sitting in the top of a fuel injector (the screen)