variable pressures with fpr shim

[norski]

Greetings! I am new to this site and I have enjoyed all the great info that is available. I have not filled out my bio but that will come. I am working on my FPR shim with a gauge. I installed the gauge before I added the shim just to see what my starting pressures were and the gauge would pulse from @ 60 to 80psi. I bled off the the schrader thinking maybe air or something had caused this but it did not change. I then went ahead and put the shim in and I basically had the same results. The shim is 3/16. Overall the truck idled just fine at both settings. What I am wondering is.. does this tell me something about the fuel pump? Nothing changed when I gave it a little throttle. The gauge is from Grainger. It is 0-100, liquid filled. Any advice? Insight? The truck is a 97 1 Ton. PSD of course. Thanks!

[marc9441]

i did mine last weekend i didnt check my pressure before starting but when i got done it was running about 62/70 psi i used the bb and it smoothed out my idle a bunch. id probable watch it for a while and if no probs i wouldnt worry about it. dont know a bout fuel pump so maybe some one will chime in that does.

[norski]

If the fuel pump is mechanical vs. electrical would that account for the variable readings? If so is there a dampener or buffer one could use? THANKS!

[marc9441]

i bought a better gauge and the needle stays on 62 lbs. no bounce. i got a 25.00 liquid gauge from an irrigation shop.like i said before dont know about the pump.

[cotton]

marc, do you know the brand/part number of the gauge?

[marc9441]

Originally Posted by cotton

marc, do you know the brand/part number of the gauge?

the only thing it sayed on the box was hecho en mexico. do you have a hydrolic shop around? if so go there they got the gauge youll need , i spent the extra money and got a stainless. if you need help i can get u one.

[alabamafrog]

97 has a mechanical pump, I have only worked on the newer 99-03 trucks with electrical pumps and the pressure is stable no matter engine rpm or if the engine is even running. I imagine the mechanical pumps will be much less stable and changed based on rpm. Maybe someone with OBS experience will chime in.