Engine And Generator Stop Running

[fnlatch]

I have a 2004 Monaco, 350 Cummins, 7.5 Onan generator.

Over the past couple years the gen would stop running. I get code 36. Prime it and it runs most of the time without stalling again. Over the years I have changed the filters, but it still stalls, but never with any regularity. I always felt that something has to be in the tank and makes it's way to the pick up tube.

Yesterday, driving back from Florida we stopped at a rest area for a break and started the gen. Started the RV and as I was pulling out everything shut down. (No warning lights, bells or horns). After sitting and running the starter on the RV, it started and while I was able to finish the trip there were times I seemed to lack power.

Today in checking it out the RV stalled twice. Have not tried the gen. No warning lights show on the dash, no warning bells. Water in fuel light does not come on (doesn't mean it's not working) Seems to be running out of fuel. Filters were changed in the early fall. I almost wish I could stick a light in the tank to see if it's clean. Plans have us heading West in mid May and really would like to solve this before.

I have a few good suggestions from Wolfe, but would certainly welcome more help in direction.

[kaypsmith]

Brett usually has best answers, but here a few suggestions. Make absolutely sure that the fuel filters are clean, take them out and closely monitor the fuel being poured into a glass jar. If any water, there will be beads at the bottom of the glass after sitting for a while. Also look for algae in the fuel, will be black ickey "for lack of a better word" substance in the fuel.

When replacing the filters, preferably with new ones again, pay close attention to your manual for replacing the filters, some manufacturers suggest different ways to prime them. Next thing to look for is seating of the filters, some use o-rings, that sometimes need replacing, as age will give up to cracking, letting air into the fuel system, diesel engines have problems with air in the system. Also check fuel lines from the tank all the engine, looking for small signs of fuel at any and all fittings.

Also suspect air filtering, clogged air filters have similar symptoms.

[huffypuff]

I have a 8k Onan generator in my 06 HR and they have it set up that the generator runs out of fuel at about 3/8 of a tank. So anytime I run the fuel below 3/8 of a tank with the coach air will get in the pickup tube and can stall the generator later when I start it with a full tank. Then I have to prime and prime again to get it going again.

The reason Monaco does that is that they think customer are too stupid and run the entire tank dry running the generator. As for the stalling problem with the engines and lack of power, I would change both fuel filters first and check if yours have a screen near the rear in front of of the transmission. When I was working fleet we got caught on a couple of those and started changing the screen on a regular basic.

[wolfe10]

Below is the reply to fnlatch's Private Message to me. BTW, I would not think this is an air related issue. Yes, air restriction can limit power, but not much air is required at idle (low RPM and no boost), so dying under those conditions would suggest other than air- related issues.

Fred,

Actually, this would make a great post-- we have several diesel techs on the forum. Copy it and paste a new thread under "engines".

But were it mine, I would start by removing the primary fuel filter for the engine and the fuel filter for the generator. Dissect them and see if there is contamination.

The other option is that there is a problem with a leak in one of the fuel lines on the suction side of the lift pump (line from tank to primary filter and primary filter to lift pump). Being on the suction side, you would not see fuel leaking out, but air can get in. Same for generator circuit.

Now, as to engine stopping-- did it just die, or did it miss before dying. If it just died, may be an electrical issue.

Brett

[kaypsmith]

Thanks Brett, really is a good post. I had a timing sensor going out on my Detroit 6V92, which is DDEC III, similar symtoms. I had system hooked up to a computer for readout, it told the entire story.

Also this computer will shut the engine down within one minute after sensing that the surge tank in cooling system is below twentyfive percent, or oil is too low.

ay

[fnlatch]

I appreciate the feed back. Ordered new filters today, I didn't want to start taking everything off before I had new ones. While looking at the filters I did notice that the drain on the primary was loose. Showed signs of having a small drip hitting the ground. Was able to tighten it a little, and placed a marker on the ground to see if anything leaks out. Plan to remove filters when new ones arrive, and the rain moves out. I'll let you know how it goes.

Fred

[wolfe10]

Fred,

Is the leaking filter the primary filter (i.e. before lift pump) or secondary (after lift pump) assuming you have two filters.

If before, a loose drain plug will leak when engine is off and SUCK AIR WHEN THE ENGINE IS RUNNING/TRYING TO RUN.

[fnlatch]

Brett

I thought the same thing. It was just a small drop, but could still allow air to be sucked. I am still amazed that it held up till I got home. Filters are in so I see if they are clogged.

Should the fuel pump stop running if you don't try to start it right away when you turn the ignition key on? Seems to me that once pressure is built up in the fuel line, it will stop until more fuel is needed. Am I right?

[fnlatch]

Took the primary off and it's totally clean. No signs of algae or water. Reinstalled it and turned on ignition. Listened to the pump and it did stop (I was able to see bubbles in the line leaving the primary fuel line). It started after a little while of cranking. Stalled after a few minutes. Removed primary and it was again full and clean. Turned ignition on again and listened, until pump stopped. It started again after a little while (longer than normal). I have left it run for 30 minutes, operating temp and seems fine.

I am happy it's running but concerned about what caused this in the first place. I drove this 1160 miles in 2 days mostly on cruise without any problem at all. At the rest area was the first sign, and then climbing our road (a steep hill) to our home. Any other suggestions? I plan on a test drive on the highway Sunday or Monday.

[fnlatch]

Took the primary off and it's totally clean. No signs of algae or water. Reinstalled it and turned on ignition. Listened to the pump and it did stop (I was able to see bubbles in the line leaving the primary fuel line). It started after a little while of cranking. Stalled after a few minutes. Removed primary and it was again full and clean. Turned ignition on again and listened, until pump stopped. It started again after a little while (longer than normal). I have left it run for 30 minutes, operating temp and seems fine.

I am happy it's running but concerned about what caused this in the first place. I drove this 1160 miles in 2 days mostly on cruise without any problem at all. At the rest area was the first sign, and then climbing our road (a steep hill) to our home. Any other suggestions? I plan on a test drive on the highway Sunday or Monday.

[dickandlois]

fnlatch,

Reading over you post and the reply's. Sounds like you have covered the engine filter(s).

You mentioned you drove over 1100 miles with no issues. Where there any grades or hills on that part of the trip?

Stopped at the rest area and the steep driveway caused issue.

Thinking, the small leak in regards to fuel can equal alot of air. Starting issues can pop up if air gets into the fuel line before the lift pump, a weak fuel pump will start the engine even with a low pressure if the fuel tank is full and setting above the lift pump.

Low fuel pressure would cause power issues when a grade is encountered and the pump can not meet the fuel demand of the engine.

The pump would be around 10 years old if is has never been replaced. How many miles on the engine? So, I would not rule it out.

Generator fuel filter or the fuel pump also need to be in good condition. How many Hrs. on the gen set?

The fuel lines can get soft and cause issues or develop leaks.

Rich.

[fnlatch]

Rich,

Thanks for your input.

The drive was from the Florida Keys to just outside Philadelphia Pa on I-95. Hills for the most part were only after the rest stop. I did not see any droplets on the primary filter when I was preparing for the drive and checking everything. May have vibrated loose, but this would be a first for me, it was still loose enough to have drops hitting the ground. Not a lot, but about a 6" circle when I went out the following morning , and that's when I saw the spot. I think the best I can do at this point is have a diesel mechanical go over the engine. I will assume they will check the fuel pump. I will ask for sure.

The generator has 491 hours on it. Oil, air and fuel filter were changed at 457 hours. I intend on doing all again before the next trip.

I have 69000 on the coach, and this is the first hiccup. I would like to get another 69000 with no more hiccups.

Again, Thanks for your time and info

Fred Latch

[fnlatch]

Rain finally gone, I was able to test drive the RV. Up and down hills, on the highway and idling. The RV ran fine, and there is no sign of leakage at the water separator bowl. Thanks Brett for the info on the air. It would appear that the small drip at the bowl was the cause for the engine shut down. Don't know how it started, but will be something I'll be watching closely from now on.

The generator is next. I'll switch out the fuel filter when doing the oil change and see if I can open up the filter for contamination. Will certainly look for air leaks while under the coach. I did pour some Bio Kleen into the fuel tank. Will let you know how things are progressing with the generator.

Brett, Thanks again

Fred

[fnlatch]

Had a chance to work on the generator. Changed the fuel filter, while I could not open it, plenty of black diesel came out. I believe the problem was algae in the fuel. After new fuel filter, the generator ran fine. I'm going to feel this solves the problem.

[wolfe10]

With the presence of algae (the black slimy stuff), you need to add a kill dose of BIOCIDE. Any marine store will have it. Biobor FJ is a common product.

Carry extra filters-- the biocide will kill the algae, but you still have to filter out the existing gunk.

To minimize algae, keep the tank full when storing it and if storing over 2 months in the summer or 3 in the winter, add a biocide.

[MadHungarian]

With the presence of algae (the black slimy stuff), you need to add a kill dose of BIOCIDE. Any marine store will have it. Biobor FJ is a common product.

Was thinking about the Biobor as well. We use this a lot when treating diesel that has been sitting in tanks for long periods of time before we filtrate. Like Brett said, carry lots of spare filters - and possibly a spare pump...... slime does a number on pump impellors...