diesel generator question

[jim rosenthal]

We just had a windstorm here in MD, and our power was out for four days. Some houses and communities are STILL out.

A few years ago, I installed a NL 16kW industrial genset; it will easily run all the loads I need inc the AC in the summer. The only problem I've had with it is that it always loses prime- I have to prime it by pumping the outboard style bulb on the fuel supply line. The fuel filter is a Fleetguard that I got from Seaboard Marine. I've never been able to figure out how to get it to hold prime. Once primed, it starts up and runs fine. Although it DID shut off once early yesterday am while I was asleep- and started up promptly again when I reprimed it manually.

With 128 hours on her now, an oil change and all the filters are due, so later this week I'm going to do that (especially as we have snow in the forecast AGAIN) but any suggestions as to what to look at to fix the problem would be useful. I think there might be a small air leak somewhere in the incoming fuel line that lets prime leak back down into the tank. The generator runs off an eighty-gallon tank that it sits on top of.

We have a very unreliable electric supply company here, BG&E, and having this generator set has saved me a great deal of aggravation in the last few years. We installed it and got the final inspection off a day or two before Hurricane Sandy, and it's been quite useful ever since.

 

[racclarkson@gmail.com]

We just had a windstorm here in MD, and our power was out for four days. Some houses and communities are STILL out.

A few years ago, I installed a NL 16kW industrial genset; it will easily run all the loads I need inc the AC in the summer. The only problem I've had with it is that it always loses prime- I have to prime it by pumping the outboard style bulb on the fuel supply line. The fuel filter is a Fleetguard that I got from Seaboard Marine. I've never been able to figure out how to get it to hold prime. Once primed, it starts up and runs fine. Although it DID shut off once early yesterday am while I was asleep- and started up promptly again when I reprimed it manually.

With 128 hours on her now, an oil change and all the filters are due, so later this week I'm going to do that (especially as we have snow in the forecast AGAIN) but any suggestions as to what to look at to fix the problem would be useful. I think there might be a small air leak somewhere in the incoming fuel line that lets prime leak back down into the tank. The generator runs off an eighty-gallon tank that it sits on top of.

We have a very unreliable electric supply company here, BG&E, and having this generator set has saved me a great deal of aggravation in the last few years. We installed it and got the final inspection off a day or two before Hurricane Sandy, and it's been quite useful ever since.

Jim, is there a chance your fuel lift pump has a hole in the diaphragm? If so, you could be leaking a bit of fuel into the oil not leaving an easy trail to follow.

 

[Bob Bradley]

Is there a reasonable way to install a check valve in the fuel line?

 

[rustybucket]

Is there a checkvalve in the circuit?

Bottom line, something is failing or has a hole in it. Is there a way you can disconnect the fuel line from the engine and the supply? if so you can plug one end and pressurize (with air) the line. Then spray dawn water on each connection until you see bubbles. Flare fittings, npt...etc all of them have trouble seating sometimes.

My bet would be on loose connection or improperly seated flare. But could also be lift pump diaphram or checkvalve (if present)

 

[Avenger]

Substitute clear hose for the fuel lines. Look for bubbles.

 

[Fish Tales]

I install home and industrial generators. Check valves usually solve the problem, and some fuel filter assy's have check valves built in. The local NAPA can assist you for that.

However, sometimes we just take the supply line from the tank, and make several loops secured by zip ties. This usually keeps fuel in the fuel line, and does not allow the fuel to drain back down. But sometimes air will still be trapped in the top of the loops, and give you fits.

Sometimes, even when running alot, a small amount of air stays trapped in the system, and has a bear of a time to being purged out. I have seen new gensets require several attempts to purge.

No leaks, just trapped air, and not enough volume of flow to push through system. Just like bleeding a non firing injector. I have had to crack non firing injectors many times to finally get all air out of system.



Good luck,
Tim

 

[jim rosenthal]

All good advice and thank you all. I'll start taking it apart and see if I can figure out where air's getting in; also there is a Parker store here and I can get a check valve to fit in the line. Should I put it before or after the fuel filter?

 

[Cricket]

My choice would be to thread the check valve into the tank pick up on the top of the tank to keep as much fuel in the system as possible.
Pick up fitting, check valve, fuel line to filter.

 

[racclarkson@gmail.com]

All good advice and thank you all. I'll start taking it apart and see if I can figure out where air's getting in; also there is a Parker store here and I can get a check valve to fit in the line. Should I put it before or after the fuel filter?

Jim, wondering if you have a Racor primary for your generator. If you do, the internal check valve should do the trick.

 

[bobk]

Jim,

A dock neighbor went through the same problem with a small SB engine. Lots of mechanics looked at it and tried all sorts of repairs to no avail. The last one noted a very slight, almost non-existent fuel sheen on the high pressure pump. It turned out there was a slightly loose screw or bolt on the pump and simply torquing it down properly with a new seal solved the issue.

Good luck,

Bobk

 

[Avenger]

Jim, wondering if you have a Racor primary for your generator. If you do, the internal check valve should do the trick.

Check valves in the fuel pump and primer bulb should too. But apparently there is an issue there.

 

[jim rosenthal]

Right, I thought the primer bulb, which does have a check valve, would take care of the problem. I use a Fleetguard filter on it, not a Racor. I'll get a check valve for the fuel line and put it on the pickup tube before the fuel line. We'll see how that does. It IS a vertical lift of the fuel, since the set is on top of the tank, but once it's primed it pulls fine. Thanks for all the suggestions.

 

[Boatsb]

Look for the bottle cap.

 

[MVCaprice]

Funny I was just talking to NL about this topic last week. Given the low hours I suspect that the lift pump is likely not the culprit. I agree with others that you may need to check for bubbles and a possible air leak in the supply line and external filter. Also agree that a one way valve may help as well if you don't already have one.

One other thing to keep in mind is that the NL lift pumps on the ML844 (which I assume you have) apparently are not supposed to have more than 18" of head lift from the generator. We have a high up generator and we use an external lift pump to assist fuel flow. With the generator sitting on top of the tank it should be ok, but if its always had an issue perhaps this is a factor?

 

[MVCaprice]

Jim, is there a chance your fuel lift pump has a hole in the diaphragm? If so, you could be leaking a bit of fuel into the oil not leaving an easy trail to follow.

Have you changed a diaphragm before? They are really reasonable (frankly the whole pump is fairly cheap) and I am thinking it may be worth a try on my ML844L as its having similar issues and I have gone through everything else already including new feed and return lines through and through.

 

[Briankinley2004]

Those primer bulb check valves are notorious for leaking. If thats the only one on your system I would look there. You could put an inline ball valve and just make sure to remember to open/close it. Check your fuel line fittings too

 

[Fish Tales]

I was thinking last night, I have also seen return lines the culprit. If the return is submerged in the tank, fuel cannot drip out and air cannot seep into the system. If the fuel line is terminated on top of the tank, it drains, and air will make its way to the injectors. That is another time the coils in the supply and return work. Fuel can stay trapped in the bottom of the coil, and cannot drip out into the tank, air cannot work its way up.

I have seen this alot on Kubotas.

Tim

 

[MVCaprice]

I was thinking last night, I have also seen return lines the culprit. If the return is submerged in the tank, fuel cannot drip out and air cannot seep into the system. If the fuel line is terminated on top of the tank, it drains, and air will make its way to the injectors. That is another time the coils in the supply and return work. Fuel can stay trapped in the bottom of the coil, and cannot drip out into the tank, air cannot work its way up.

I have seen this alot on Kubotas.

Tim

Conversely if you don't have air that can come into the return line can't you get a vapor lock? I bet that makes purging air out of the system difficult.

 

[Fanfare]

Some fuel pumps appear symmetrical but they are not. They only go together one way with their several layers. Draw a line from top to bottom with magic market before disassembly. Then only the new piece needs to be fitted. Otherwise you have multi layer rubics cube.

 

[jim rosenthal]

Those primer bulb check valves are notorious for leaking. If thats the only one on your system I would look there. You could put an inline ball valve and just make sure to remember to open/close it. Check your fuel line fittings too

This also occurred to me. I'll either fit a check valve or a shut-off valve.