Question about the diesel filter system on the boat

[Tartan34C]

I went out today and escorted a group of kayaks during a 9 mile race. It was a tough job but somebody had to do it so I volunteered. Everybody had a great time.

But I have a question about the filter system on the boat. We just replaced the engine with a DH225 Volvo diesel. The filter system is designed to have the flow in one side until a vacuum gauge registers increasing vacuum and then you switch to the B side and change the filter in the A side. The engine is all electronic and has sensors for everything. During the day, after running for 4 hours the engine warning system sounded with an error code indicating fuel problems. The engine automatically reduced speed and when I switched to the B filter speed picked up and the warning system became happy again. We had a fuel problem before and had the tank cleaned but clearly we have the problem again. My question after all this typing is very simple. The vacuum gauge only showed an increase of 2 pounds. Is that all it takes or is the gauge misreporting the vacuum?
Thanks and all the best,
Robert Gainer

[sailingdog]

Vacuum pressure for low-pressure fuel pump isn't very high... Atmospheric pressure is only 14 PSI or so. If the pressure is at 4 PSI, and goes to 6 PSI, that's a 50% increase in fuel pump pressure. If you're at 2 PSI and have a 2 PSI increase, you've doubled the pressure.

BTW, mechanical fuel pumps typically run between 4-6 PSI, electrically driven fuel pumps are made as both low-pressure and high pressure models. The high pressure ones often operate at pressures of roughly 30-40 PSI.

Note: This is from my days as a gearhead, working on cars, and the marine specifications might be a bit different, but I highly doubt it.

[Valiente]

Originally Posted by Tartan34C

My question after all this typing is very simple. The vacuum gauge only showed an increase of 2 pounds. Is that all it takes or is the gauge misreporting the vacuum?
Thanks and all the best,
Robert Gainer

I can't address your particular system, but I can say that the mechanical fuel pump in an Atomic 4 creates a mere 2 PSI of pressure drawing fuel from the tank, and that I can believe it because a spider-web-clogged tank vent line can gradually overwhelm this cam-driven diaphragm pump.

So I can believe that the difference needn't be huge between sucking and blowing on your diesel's fuel system...so to speak.

[sandspur]

Change the A filter may be a bad filter or clogged , Check the sensor at A filter & wires + plugs, This can be done with a multimeter, must likely a bad sensor