Getting fuel to the generator

[crayiii]

My generator saga continues...

I'm not thinking that our diesel generator is starving for fuel after running for awhile (about an hour).

The generator is about 45 different like feet horizontal from the tank and 6 feet vertical.

At the mid point (20 feet horizontal and 3 feet vertical), is a Facet Cube fuel pump. Next to the generator is a Racor 200 that feeds the mechanical fuel pump on there generator.

I just replaced the Facet come with a larger one that is rated at 33gph and up to 7psi but the problem persists.

When started cold, the generator will run perfectly smoothly for about an hour no matter what the load. A perfect 3600 RPMs up to 85% load (I don't have more load to give it).

After about an hour, the engineer will drop 100 RPMs than bounce back, then 150 RPMs and bounce back with no load changes and repeat every couple of minutes.

Just before the engine does this the Facet pump starts knocking very loudly then quiets back down to a whirring sound.

I'm really hoping someone has some ideas on this. I'm wondering if I'm asking the pump to lift the fuel too high. I'm worrier about putting too much pressure on the racor though.

[Paul L]

You could try running out of a diesel jerry can close to the filter and see if you still experience the problem.

[Diesel Bill]

Hi crayiii, only things I can think of is suction in the tank plugging up or air being pulled into the line some where. these are the most common .

[a64pilot]

The knocking loudly is almost certainly air and or fuel vapor which acts the same.
The closer to the fuel tank the better for the pump, pumps well pump better than they can suck.
7 PSI is in my opinion plenty, you shouldn’t need more than that. Some will tell you the filter needs to be on the suck side, that’s for safety cause a leak just sucks air as opposed to spraying fuel.
I’d start by ensuring the tank vent isn’t plugged, then pull the dip tube and ensure it’s not blocked by anything.

Th pump rattling is why I’m not suspecting the generator itself. I think that pump rattling is key to the problem.

[pesarsten]

I had a vacuum leak at my raycor 500 fuel filter. Took forever to find it. Similar symptoms to yours.

[Nicholson58]

Originally Posted by Paul L

You could try running out of a diesel jerry can close to the filter and see if you still experience the problem.

This is good.

Note that the Facet pumps have a pressure output rating as you stated. They also have a suction lift rating. Some facet pumps also have an in line small suction filter. If you are borderline anywhere in the suction side it might cavitate. This might be what you hear. You can find the ratings chart on the Facet site.

[GordMay]

Because pumps emulsify water, Parker-Hannifin (Racor) recommends that fuel transfer pumps be placed on the vacuum side (after) the filtre.

[Hesti]

Tank ventilation has been mentioned, it is a very likely cause.



How is the fuel temperature when the problem starts? As Diesel engines often pump excessive Diesel back into the tank or the filter, there can be situations, where the temperature on the suction side of a pump raises over time. This can support the forming of bubbles on the suction side.

[crayiii]

More data:

It's a catamaran and there are two tanks. The problem is the same regardless of which tank is being drawn from. There are selector valves for fees and return.

The boat is 2 years old.

There is a return going to the secondary filter on the generator and there is also one going back to the tank.

I plan on removing the pickup pipe and looking at it today. If it has a screen, should I remove it?

After that I'll run the generator and if it starts having the issue again, I'll open the filler on the tank to see if it's a vacuum on the tank. The main engines haven't had any issues so I don't think that is it.

[crayiii]

The tank vents are clear and the pickup looks to okay. I'm beginning to think it's the dry lift capability of the Facet pump. On their website it's listed as Lift Min: 60"

I'm guessing that means it can lift 60 inches but I don't know what the "Min" means.

I'm trying to lift fuel about 80 inches.

[billknny]

Originally Posted by crayiii

More data:

I plan on removing the pickup pipe and looking at it today. If it has a screen, should I remove it?

NO! NO! NO! If it has a screen, and the screen is clogging, fix the problem not the symptom. Clean the crud out of the fuel tank!

Did this setup ever work correctly? If yes, then re-jiggering the plumbing isn't the answer. Find what has changed. If this is a new installation and has never actually worked, then the design and/or installation is faulty. Start from scratch.

Does the problem change with the level of the fuel in the tank? Where is the pump relative to the tank? Is it above or below? If the pump is 80cm ABOVE the level of fuel in the tank, that's your problem. When the mfg specifies the pump will lift "60cm minimum", that's what they mean. It will lift 60cm, and maybe more, but they won't guarantee more. It's not rocket science.

The symptoms you describe are 100% consistent with one of three problems. A pump above the tank losing prime, or An air leak in the suction line to the pump, or a clogged vent on the fuel tank and drawing a vacuum. But that would affect the main engine as well, so isn't very likely. But it is trivial to test, just run with the fuel tank fill open.

Since the problem comes with BOTH fuel tanks, the smart money is betting the problem is somewhere between the selector valve(s) and the suction pump.

If you temporarily insert a piece of clear hose right before the suction pump, you'll see the air bubbles from a leak. That can make it easier to track down.

Finally, your pump and filter are in the wrong order. As has already been pointed out, the filter should always be BEFORE the pump, under vacuum, not pressure--for lots of very good reasons. Installing things in the reverse order means the person who did the installation does not know or understand marine fuel systems. There are likely to be other errors, that might or might not be obvious, some potentially dangerous, others (as you are experiencing) just annoying.

[crayiii]

It worked with a different pump in the system (Carter) but started doing this a couple months ago and I noticed the Carter pump went from noisy whirring to almost silent so replaced the pump thinking it was faulty (still think it was) but I can only find these small pumps here in Grenada.

[a64pilot]

I wouldn’t worry about moving the pump and filter if I were you. Yes a pump can emulsify water, any physical movement etc can emulsify fuel. I’d suspect fuel sloshing around in the tank may be more likely to emulsify water than a pump.
A Racor if you use the Racor cartridge will remove emulsified water, it won’t remove much, it clogs when it does, but it will remove emulsified water, and of course free water.
Often when a Racor clogs but looks not that dirty, it’s emulsified water that has clogged it, the filter element absorbs the water.

[Michael Pope]

OKmso Iam old soIcan perhaps be excused a scoche for saying WE HAVE BEEN PUMPING STUFF NOT JUST FLUIDS FOR OVER TWO THOUSAND YEARS ___ SO FOLLOW THE RULES ipso Pump goes at the lowest point in the circuit --NO IFS AND BUTS!! If the fluid needs filtering (nearly all do) put an oversize (Large filter surface) filter just before. the Pump.. This is where it will leak air or a vapour lock into the system so make it quality and accessible. If possible put a transparent sump or filter bowl just adjacent to the primary (Large filter area) filter with the bottom of the bowl visible (if necessary with a mirror) lower than the filter intake Tnen any water or solids will show before they are ingested and possibly can be drained out with a small tap and catchment. If you can get the pump sucking happily away you have overcome 90% of all the fuel problems in the world the pressurised side is easy ----it will squirt in your eye!
Usually keep running even if leaking.. The suction side needs loving care in Installation!
I ft is Gasoline and particularly if it is diesel THERE ARE THINGS THAT WILL GROW IN IT IF IT has been there a wile nasty Jelly like things very hard to get rid of circulate your fuel through the filter regularly. if the system is large put a solenoid (or Manual) bypass valve so even if you do not need the engine you can circulate the fuel for an hour every day! Then have a schedule for cleaning or clearing the filter once a week / month/ whatever but scheduled! Pax Vobiscum ! Da Pope