Fuel Filter Restriction/Lift Pump Psi Gauge Kit for Duramax
Gauge use notes:
The Duramax engine has a factory installed test port alongside the alternator. Simply remove the cap and snap my gauge onto this port and start engine. It is important to establish a baseline with clean filter(s) a full tank of fuel and on level ground. This eliminates variables in effort required to move fuel. Restriction can be checked at idle speeds and at 2-3,000 RPM. Typically we will see approximately 2-4″hg at idle with very little variance as RPM increases. As a filter loads up, you will see restriction increase. When you hit about 5-6″ hg (about 2″ above baseline) I consider the filter well used and due for replacement. The early Dmax single layer media filters would run a long time without much of an increase in restriction. The latest multi layer media units seem to be doing a much better job of collecting dirt, but start at a higher restriction that rises quickly as they load up. Having this gauge on hand allows you to quickly and easily verify the condition and can be very beneficial when diagnosing fuel system related drivability issues. Typical OE filter life is < 15,000 miles. We have seen these filters load as early as 2500 miles or less depending on fuel quality.
This is a flow checked device much like an air hose. It will not return to zero unless the center valve core is depressed. Additionally, the gauge housing is liquid filled so temperature/pressure changes can affect the zero point. There is a plug on the back of the gauge head that can be vented to allow equalization between the gauge and atmosphere, but be careful not to damage the plug or let the glycerin run out.