CSX 4000 Fuel Pressure Gauge Dancing

[sfm5s081]

Just wondering if the fuel pressure gauge, Smiths, is supposed to be erratic and constantly moving all around. You can get a good idea where the fuel pressure is, but the needle jumps around. Is this right? Or do I need to have the gauge rebuilt

[shelbydoug]

Why do you presume that the gauge is not being accurate? It may be telling you exactly what is going on with the fuel pressure.

If so, every component of the system is now in question. You need to check them one by one.

[Bob Gaines]

Just wondering if the fuel pressure gauge, Smiths, is supposed to be erratic and constantly moving all around. You can get a good idea where the fuel pressure is, but the needle jumps around. Is this right? Or do I need to have the gauge rebuilt

Some gauges react to the pulses of the fuel pump as a slight jump between pulses. Some gauges more then others . It might not be a defect .If the same gauge has changed from doing one thing and now does something else all other things being the same then that would indicate a faulty gauge .

[pbf777]

     If the gauge is just being over-reactive to pressure bounces invariably present with the mechanical fuel pump, this can generally be dampened out by inserting a restriction orifice in the supply/sensing line to the gauge.  One may need to experiment with orifice dimensions until you acquire the effect as desired.   

     Scott.

[CSX2259]

If the fuel line fitting is easily accessible, because I know the fuel pressure gauge is not, I would try another gauge at that point and see if the gauge responds in the same way. If it does you have an issue with another component (fuel pump or?) if the needle remains steady then you know it is the gauge.