Racor Vacuum pressure unchanged post new filter installation

[Raylee]

We changed the 2 engine racor filters today. The 10 micron old filters showed vacuum pressure of 4 on the scle, the yellow region starts at 6. The old filters had been in use for 18 months, they looked somewhat stained with minimum debris. Installed new 10 micron filters, ran the engines fir a few minutes vacuum pressure now shows 5 and 4.5 on the scale so basically unchanged or worse. Racor information recommends changing the filters at 6-8 on the scale. We change them every year or 18 months based on how much use.

Should we have seen a drop in the vacuum pressure with the new filters?

Thank you in advance for your comments or ideas.

Raylee

 

[O C Diver]

Understand that the gauge measures vacuum. As a result, vacuum can be a dirty filter element, or lifting fuel from a lower level to a higher level. So, if your fuel level in the tank is quite low, lifting it up to the Racor filter will generate vacuum. If you can estimate the difference between the fuel level in your tank and the level of the lift pump on your engine, that may help answer the question.

Also, it's important to know whether the vacuum was at idle or cruising RPM. An engine that has low vacuum at idle and significantly increased vacuum at higher RPM, can have fuel line restrictions (partial blockages) that show at higher flow rates.

Ted

 

[RT Firefly]

Greetings,
Mr. R. The Racor filter mounted, oil filled gauges on our last boat had to be "burped" after filter change or when needle didn't go back to zero. Rubber plug on top of gauge had to be shifted slightly to allow a bit of air back into top of gauge. Do NOT allow rubber plug to "sproing" away.
I used a small pick to gently move the plug enough to allow needle to reset while carefully holding onto it (it's oily and slippery).

 

[Steve DAntonio]

RT, you beat me to it. Better vacuum gauges have a tiny yellow handle valve here to equalize air pressure.

While the engine is idling, slowly close the fuel supply valve feeding the filter, you should see the vacuum begin to rise. Doing this will confirm the gauges aren't seized.

More on Vacuum gauges here (and the valve-equipped gauge is the first one shown in the article) The Invaluable Fuel Filter Vacuum Gauge – Editorial: My Kingdom for a Set Screw… | Steve D'Antonio Marine Consulting

 

[RT Firefly]

Only by 2 weeks...

 

[SeaGator]

What micron element does your engine manufacturer call for? In many cases the primary Racor should be 30.

 

[Lepke]

I use 2 micron elements in my Racor housings and a new filter reads zero.
I suspect if the gauge is right, there's a restriction before the Racor or the fuel line, valves are too small.