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Old 05-07-2022, 11:04 PM   #1
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Another generator that won't turn over

I have a Gulfstream diesel motorhome with a front mounted Generac NP-66G that originally worked flawlessly when I got the coach last year.

After this past winter, all of the remote control buttons (3 of them, located in the coach) stopped functioning. The switches work fine (tested them) and the generator would start using the generator mounted starter button. The fuse on the generator near the starter switch was (and still is) fine. I did notice water inside the Monoplex Gen-Set 2 module box (pictured). I have tested a few of the resistors and they seemed fine, but there are so many things on there that could have failed I'm just assuming this board is fried.

At this point, the motorhome's power switch was functioning correctly (which tells the coach where to get power from), but the Intellitec box which connects to the generator and allows you to use both AC units on gen power is not working entirely. I was unable to use both AC units while the generator was on, and I'm guessing that is because the Monoplex circuit board is fried?

Today I ran the generator and it started almost instantly using the main gen start button. Later, I was trying to get the generator to start by shorting two wires, and I tried shorting the 12V end to the Start end of the wires that plug into the monoplex board. Absolutely nothing happened when I did (no sounds, clicks, turns, sparks, nothing at all).

Eventually I tried to start the generator again from the main switch on the unit itself, but I only heard the CLICK from the starter solenoid (pictured below the START/STOP switch on the gen), as well as a typical electrical hum as I held down START. But no sound from the starter. Typically if the batteries were low, it would slowly turn, or even make this grumbling kind of noise. But that is not happening now (and again, it started fine less than an hour before).

So I'm pretty sure the wires are all good and the ground connection is fine, considering it started up great about an hour earlier. I did absolutely nothing other than fiddle with the remote start wires. House and chassis batteries are fully charged. I feel like it could be the starter motor, but why would it die randomly like that, without any warning at all? Again the solenoid makes a very loud CLICK when I try to start it, so while it does look old (pictured), it was working fine and seems to be clicking fine still.

Aside from the starter, what else could it be? I will try to take it apart tomorrow, but I cannot tell where the starter is located (the solenoid has a wire which goes somewhere; can't quite tell where it goes...). The remote start is something I want to fix, but at this point, I need to figure out why it won't start at all. So the monoplex gen set circuit board isn't too important. FYI, before today, the generator would start and provide 120V to the coach with or without the monoplex board plugged in.
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1993 Gulf Stream Scenic Cruiser diesel pusher, 5.9 Cummins, 6 speed Allison. I tend to act before I think. It gets me into trouble, and so I end up here in the forums asking for help. I learn the hard way. Thank you all for your help.
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Old 05-08-2022, 08:37 AM   #2
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You are all over the place with your troubleshooting logic - you need to locate the common denominator to what the problem is and that is the genset.

Assuming the batteries are fully charged (which I am suspect based on some of your comments) - it sounds to me like either the starter solenoid is bad or there starter is bad.

If you attempt to start the genset using a switch, and you hear a click or clicking - is an indication of either of the above scenarios.
The current carrying “disc” inside of the starter solenoid could be carburized or its travel somehow limited so that it doesn’t fully close. A carburized disc or one whose travel is somehow limited (due to wear or intrusion of dirt) can be the cause of intermittent operation.
Or, the commutator and brushes inside of the starter may have issues - and if intermittent as you describe it could be a bad spot on the commutator or worn out brushes.

But after you confirm that all control side circuits (including switches) are working properly, then you need to start looking at the real “power” battery side circuits.
In confirming the control side circuits, you may have intermittent issues that are difficult to confirm. But - the power side battery circuits (which include the starter solenoid and starter) are very easy to confirm their proper operation.

It is possible but unlikely one of the circuit boards is “fried”. Just because you don’t understand something and how it works doesn’t mean it’s broke (or “fried” as you say).

Get the battery power side circuits working with a known reliability and a known fully charged battery first. Once you’ve got that done, only then should you chase the control side circuits.
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Old 05-08-2022, 10:32 AM   #3
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The best approach to diagnose anything that isn't working properly is to first eliminate what isn't the problem and that will point to what's left that's causing the problem.

This removes guess work.

Be methodical step by step.
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Old 05-08-2022, 01:00 PM   #4
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May be nothing, but I see evidence of a hot spot on the board.
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Old 05-08-2022, 07:47 PM   #5
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The solenoid works as I am measuring voltage at 13v approx. The starter is just too hard to get to. But behind the generator itself I can felt a large cylindrical object about 10-12 cm in diameter and it gets hot when I try to start the gen, well above 50-70C after holding start down. I simply cannot get into that area without removing the gen which is extremely difficult, but I did tap and hit it with a hammer and it did nothing. More than that, I don't know, and I'll have to let this one go. I'll likely buy a portable generator for the foreseeable future.

Given that what I think is the starter is getting hot, it must be the starter that's gone bad and can't rotate, or the engine is siezed (which I doubt because it ran perfect 30 min before).

I'd bet the starter is the culprit but due to the difficulty in removing it, we may never know. And yes batteries are fully charged. I specifically stated that was not the issue.

The circuit board and remote start is trivial compared to this issue now.
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1993 Gulf Stream Scenic Cruiser diesel pusher, 5.9 Cummins, 6 speed Allison. I tend to act before I think. It gets me into trouble, and so I end up here in the forums asking for help. I learn the hard way. Thank you all for your help.
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Old 05-09-2022, 08:40 PM   #6
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10-12cm in diameter sounds big for an Onan starter although I have never put my hands or eyes on one.
I would expect it to be more comparable to a >16 - 25 Hp riding mower starter.

You are correct in that the engine probably isn’t seized since it ran.

And, after letting the generator sit overnight - after 1 attempted start - is the starter motor immediately hot, or does it take 3 - 5 attempted starts? Is it so hot that you can’t keep your fingers on it, or is it just warm, or slightly warm?
If hot, the starter either has a shorted winding or possibly a burned place on the commutator. Either requires access to the starter.

As for buying an “Off-the-shelf” genset from a big box store or a place like Harbor Freight or Northern is those gensets are built mostly for backup or short term use. Their duty cycles are not near what is typically needed for a MoHo.
You can use one, just know what their limitations are.

Short of taking the coach somewhere for the genset to be repaired - ingenuity and tenacity will be needed to figur out a way to get that genset out of the coach.
Some require a floor jack of sorts to drop the genset straight down. Others use a hinged picture frame that the genset sits in the frame and hinges on the backside of the genset with bolts on the front that are removed to allow the genset to hinge down on the curb side of the coach. It would then need to be unbolted and removed from that frame for subsequent service and operation.
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Old 05-10-2022, 04:33 AM   #7
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There are four corner bolts attached to the chassis frame along with four rubber engine absorbers from what I can see. The generator seems to also be sitting on a flat piece of metal (a plate) to protect the bottom. I imagine the whole plate could drop down along with the generator, or the gen will come out of the front bay. Honestly I have nothing to lose at this point, and I'll give it a try.

What I meant was I'll just buy a portable RV generator to use for now while boondocking.

The starter got hot after multiple starting attempts. I'd hold it down over and over a few times and it would warm up. Eventually I would smell a burning kind of smell. Not quite rubber but mind of metallic and rubbery, if that even makes sense. I didn't try to touch it when it smelled bad, but I would say after 3 or 4 attempts at holding start down, it got quite warm. I measured around 60C with a temp gun. But not overly hot that it burns on contact. I don't know about when it started to smell bad though.

Also the size may not have been that big. It was really hard to tell because of the position I had to hold myself in and reach into to feel it. It could have possibly been 5-10 cm. Reasonable for a starter motor. I know the in starter must be back there as I can see the solenoid wiring leading back there.

Anyways, I think I can reasonably attempt removal, just not in the next short while. Once I do get around to it, I'll update this thread. Thanks all.
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1993 Gulf Stream Scenic Cruiser diesel pusher, 5.9 Cummins, 6 speed Allison. I tend to act before I think. It gets me into trouble, and so I end up here in the forums asking for help. I learn the hard way. Thank you all for your help.
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Old 05-10-2022, 04:47 AM   #8
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We’re here to help whenever you get around to it.

Sometimes the Owner Manual describes genset removal.

It does not sound like the starter is getting overly hot. The reality is - starters do get hot - you always have to keep in mind there is a lot of energy being consumed in a very small space within a starter. And if the starter doesn’t turn, all the consumed battery energy remains inside of the starter as opposed to being used to turn the engine. Something akin to what happens when you short across the battery terminals of a battery (not recommended to attempt!).

Understood on temporary genset use (you have to do what you have to do) - just fair warning on what to expect with what you get.
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Old 05-17-2022, 11:50 PM   #9
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Hi again all. I am still learning a lot about small engines, and I was thinking about something I recalled when I took the top cover off of the gen. Should the flywheel have even a bit of wobble or play in it? I ask because when I took the cover off, it was completely solid. Would not rotate at all, not even a few millimeters.

Is this normal?
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1993 Gulf Stream Scenic Cruiser diesel pusher, 5.9 Cummins, 6 speed Allison. I tend to act before I think. It gets me into trouble, and so I end up here in the forums asking for help. I learn the hard way. Thank you all for your help.
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Old 05-18-2022, 02:04 AM   #10
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You should be able to rotate the engine full revolutions by hand, although with some difficulty on the compression strokes.
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Old 05-18-2022, 04:41 AM   #11
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Thanks twin. I'm going to take a look soon and see if I can move the flywheel. I didn't give it much thought at the time. I tried to move it and it was really sturdy, so i thought "can't be the flywheel, it won't budge, must be inside". I found out later (once I put it all back together) it was the flywheel.

Suppose I cannot budge the flywheel one bit. This would explain the starter not turning. What could have possibly caused something being seized?

I feel like it's not likely the starter would die in one afternoon, after working flawlessly for years. But I feel it's even less likely the engine would seize one day after working fine just minutes before.
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1993 Gulf Stream Scenic Cruiser diesel pusher, 5.9 Cummins, 6 speed Allison. I tend to act before I think. It gets me into trouble, and so I end up here in the forums asking for help. I learn the hard way. Thank you all for your help.
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Old 05-18-2022, 05:12 AM   #12
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Seized engine, seized generator head bearings, hopefully jammed starter or jammed starter gear into flywheel.

Look at the oil, a bad engine may show metal in it.
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Old 05-18-2022, 08:08 AM   #13
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twinboat pretty much said it but let me clarify some things -

You said the genset ran -

1. Did/does it have plenty of oil in it?
2. Do you see any metal fragments in the oil?
3. When the engine quit running did it make any unusual noises or sounds, and/or emit any burning odor and smoke?

Most small engines can be turned by hand at the flywheel, some easier than others - it all depends on your skill set of being able to grab and turn it. However, if the starter is somehow still engaged with the flywheel - I have found some flywheels that wouldn’t budge - making the engine feel as though it was seized up.
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Old 05-18-2022, 06:33 PM   #14
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maybe the engine is hydrolocked from a cylinder full of diesel fuel.
Can you get to the glow plugs to pull them See if the flywheel turns after that
Sounds like a injector leaked after shutdown

Just my .02 c
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