Failure of fuel suction gauges?

[SuzieWong]

The boat has two SBMAR double filtration systems with suction gauges for the engine fuel system. Appears both system (all four indicators) have failed:
- System A shows high negative pressure despite system depressurized, aired, filters removed and valves wide open
- System B shows no negative pressure in fuel supply line despite engine starving of fuel. Bypassing the fuel filters and the engine runs fine.

This makes me wonder how reliable SBMAR suction gauges are.
Can anyone else report failures on these?
Indicators had been lying around in hot and humid conditions for years - due to shipyard's neglect. Could that cause failure of these (not cheap) indicators?

 

[PM]

Mine have never failed. I rarely look at them though.

I looked one time when my engine had "starved" due to a closed fuel line. Sure enough it was in the red.

pete

 

[C lectric]

Never heard of problems and I frequent both the Seaboard and Boatdiesel forums .

If the guages are not working and you say the boat sat for many years then maybe diesel fuel has gelled in the sensing port in the stem of the guage. It can form a sort of varnish which will plug the port. That gelling is NOT the guages fault, rather the owners lack of use which allowed the gelling to occur.

THese ports are usually small.

Take the guages off and examine for the opening in the threaded stem. I will guess that the port to the actual mechanism is plugged so the guage cannot sense the vacuum.
I doubt the actual mechanism has failed, especially all four of them.

You may need a needle to poke a hole in the old diesel buildup or better yet a
small drill bit which will pull the buildup out.

I have two of these guages at home so checked the sensing opening. A 1.5mm to 2mm drill bit should do the job. Start with the smaller first. Be carefull to just drill through the varnish buildup and not damage the mechanism. I suggest what is called a Pin Vise to hold the bit but some care and a pair of pliers should do the job also.

A good hardware store, auto parts store should have these drill bits. Ask around the marina as there is a very good chance that a dock neighbour will have drill bits suitable.

 

[Bmarler]

The filter housings might be crudded up too. I’d take them off the boat, clean them out well, and blow compressed air through all the passages. Think about re-installing with new fuel hoses.

 

[twistedtree]

With both gauges failed, I wonder if they are exposed to unusual vibration? Are they engine mounted, or hull mounted?