Generator starts, runs, then dies

[Henry J Fate]

170 volts is a problem. replace the regulator.

65hz is also high indicating the rpm of the engine is too high.

the 130 volt reading could be enough to immediately shut the the generator off. 170 and its definitely shutting down.

my 2001 microquiet will shut down on 3 seconds of 66-69hz . if it hits 70, shuts down immediately.

you do have a rpm problem. there should be an adjustment for that. find it and turn it down some. go in small increments.

 

[MGH]

170 volts is a problem. replace the regulator.

65hz is also high indicating the rpm of the engine is too high.

the 130 volt reading could be enough to immediately shut the the generator off. 170 and its definitely shutting down.

my 2001 microquiet will shut down on 3 seconds of 66-69hz . if it hits 70, shuts down immediately.

you do have a rpm problem. there should be an adjustment for that. find it and turn it down some. go in small increments.

Thanks, Henry!

I finally discovered how to adjust the engine rpm. That set screw had been staring me in the face the whole time.

Over-adjusted down at first, then brought the frequency back up to almost 60 Hz, but Volts are still way too high.

Looks like a new voltage regulator is going to have to be the next step, unfortunately. Any other thoughts to save a few hundred bucks... or confirm the issue and help me feel better about spend it?

Thanks again, all

Here's the current state:

 

[Henry J Fate]

lets see what the results are with a new regulator. once you get the voltage settled, final rpm adjustment can be done with a good load on the generator.

 

[RayNorthernWI]

I agree with Henry, your engine RPM is off. It should be at 3,600 to make 60 cycles. After that overvoltage is a diode or regulator issue.

 

[MGH]

I agree with Henry, your engine RPM is off. It should be at 3,600 to make 60 cycles. After that overvoltage is a diode or regulator issue.

Thanks for following up. I did install a new voltage regulator a couple weeks ago (from Flight Systems). Hz were still okay, running right around 60 +/- 1. Voltage was better, but still high, started in the high 120s, then rose (slower than before) to ~140 before I released the start switch and let it shut off.

So the new regulator seemed to make at least some difference, but did not solve the whole issue. I haven't had much time since then, and probably won't over the next month or so.

Could you explain more about the possibility of a diode issue?

Thanks again.

 

[MGH]

I'm trying to make some progress again on this generator. Over the last few weeks, one of the Flight Systems technicians was helping me troubleshoot via email. As I was having the same symptoms with my original and replacement voltage regulator, we moved on and isolated things down to step 8 of this governor troubleshooting guide: https://www.flightsystems.com/pdf/marquis-governor-troubleshooting-guide.pdf

As described in the above guide, I was able to simulate the enable signal. Doing so, the generator ran at a constant speed and produced a steady 122VAC. This, according to the troubleshooting guide, likely means my governor is bad. I sent it in Flight Systems to bench test, and everything tests fine – which is actually disappointing as we still don’t know what the issue is. The Flight Systems tech has no more suggestions for the time being.

I’ve started trying to trace wires, especially from the oil pressure switch to control board, to see if there are breaks or shorts. I’m not having much success as the wire runs quickly disappear behind other components. I’ll keep at it; will probably have to get very well acquainted with the wiring diagrams so I can figure out where the wires are supposed to go, and then go look for them there. Beyond that, I’m considering I may have no other option but the parts canon, and shoot a control board at it, and maybe a new governor as well (even though my unit tested good).

I’m sorry I don’t have much more new detail to go on. If anyone reads this thread and has other ideas, I’m all ears.

Thank you,
Matt

 

[zulu]

If anyone reads this thread and has other ideas, I’m all ears.

Did you test for a clogged fuel line?

Fairly simple . . . disconnect gen fuel line, attach a hose to another fuel source (small gas can), try powering up gen.

 

[MGH]

Did you test for a clogged fuel line?

Fairly simple . . . disconnect gen fuel line, attach a hose to another fuel source (small gas can), try powering up gen.

I did exactly that earlier on. Fuel runs through fine. And as above, with the enable signal manually applied, the generator as a whole runs fine too. I'm pretty sure I've excluded the fuel system as the issue.

 

[Lou Schneider]

I’ve started trying to trace wires, especially from the oil pressure switch to control board, to see if there are breaks or shorts. I’m not having much success as the wire runs quickly disappear behind other components. I’ll keep at it; will probably have to get very well acquainted with the wiring diagrams so I can figure out where the wires are supposed to go, and then go look for them there. Beyond that, I’m considering I may have no other option but the parts canon, and shoot a control board at it, and maybe a new governor as well (even though my unit tested good).

Eliminate the simple things first. Pull the wire off of the oil pressure switch and run the engine. If the engine keeps running past the normal shutdown point you either have low oil pressure as the engine warms up or a defective oil pressure switch. Also verify the engine shuts down with a low oil pressure fault if you touch that wire to ground. This will verify the wire is working properly.

Onan recommends using straight 30 weight oil unless you're running the engine below freezing. It's thicker than multi-grade oils until the engine reaches operating temperature. Air cooled engines have wider internal tolerances when they're cold. Maybe you're hitting a point where the thinner multi-grade oil is letting the oil pressure drop too low as the engine warms up and switching to 30 weight oil may get you over that hump.

 

[MGH]

Pull the wire off of the oil pressure switch and run the engine.

I was about to say, "Thanks, but nope, I've tried that already, AND replaced the oil pressure switch anyway."

But because you said it I tried it anyway. The generator started, ran without having to hold the start switch down, produced 120V, and kept running for ~25 minutes.

I could swear I really had tried that before. And yes, I did replace the oil pressure switch in April this year. Regardless, I don't know what's going on, and need to keep trying whatever I can.

Here's what happened today, then:
- Generator ran on its own, with oil pressure switch unplugged, for ~25 minutes, as above.
- Generator produced a constant 120V while running.
- I started the rooftop A/C fans (fans only) one at a time. Front on low, then high. Then added back A/C on low, then high. Voltage remained at 120V throughput, as measured at an interior outlet.
- Switched the front fan off completely, then set the back A/C to Low Cool. The ECCEM system ran through its typical ~1 minute delay...

But then:
- The A/C unit shut off completely
- And there was a buzzing from the coach breaker and fuse panel.
- The generator continued running, but I had no more 120V in the coach.
- I shut off the generator by reconnecting the wire to the oil pressure switch.
- With oil pressure switch disconnected again, the generator will restart, but only run for a few seconds before shutting down.

That's all I had time for tonight.

The rooftop A/C units are both one year old, and have always worked fine on shore power.

Anymore insight about what's going on?

Thanks.

 

[Lou Schneider]

I was about to say, "Thanks, but nope, I've tried that already, AND replaced the oil pressure switch anyway."

But because you said it I tried it anyway. The generator started, ran without having to hold the start switch down, produced 120V, and kept running for ~25 minutes.

I could swear I really had tried that before. And yes, I did replace the oil pressure switch in April this year. Regardless, I don't know what's going on, and need to keep trying whatever I can.

Once again, what viscosity oil are you using? Onan, Volkswagen and other manufacturers recommend single grade SAE 30 weight oil in their air cooled engines except in sub-freezing temperatures. Multi-grade oils like 5-30, 10-30, 15-40, etc. are thinner than 30 weight oil until they get up to full operating temperature and while this is preferable for the tight tolerances in modern water cooled engines they will will generate less cold oil pressure in air cooled engines.

From Page 6 of the Operating Manual, Engine Oil Recommendations:

"Single grade oil SAE 30 oil is preferable when temperatures are consistantly above freezing. Multigrade oils are better when large temperature variations (i.e. sub-freezing temperatures) are anticipated."

 

[MGH]

Once again, what viscosity oil are you using?

I've been using 15W-40. I know I saw it in the table in the manual - and recommended in some guy's video on YouTube .

But you're right [again], Lou. Still I'm genuinely trying to understand what's going on here. If the difference in the oils is that my 15W-40 would produce less pressure when cold, why is it that my generator started and ran fine from cold, but not when already hot?

Also, given that I was starting and running without the oil pressure switch connected, would the oil viscosity even make a difference (besides overall engine wear and performance)?

Again, I'm not trying to argue a point. I don't know what's going on, and really want to understand it.

Thanks again.

 

[Lou Schneider]

I've been using 15W-40. I know I saw it in the table in the manual - and recommended in some guy's video on YouTube .

But you're right [again], Lou. Still I'm genuinely trying to understand what's going on here. If the difference in the oils is that my 15W-40 would produce less pressure when cold, why is it that my generator started and ran fine from cold, but not when already hot?

Also, given that I was starting and running without the oil pressure switch connected, would the oil viscosity even make a difference (besides overall engine wear and performance)?

Again, I'm not trying to argue a point. I don't know what's going on, and really want to understand it.

Thanks again.

You're welcome. I've had this happen to me on an Onan generator.

As to why the type of oil matters, air cooled engines can't control their temperature as precisely as liquid cooled engines. Metal parts expand as they're heated, so air cooled engines need to start with more clearance in their nternal parts so they will continue to fit together properly as the engine heats and the parts expand. This means air cooled engines need a thicker oil than the multi-grade oils can provide until they get up to operating temperature to maintain oil pressure while the parts are expanding at different rates.

As it turns out, for an air cooled engine single weight oil follows this changing viscosity requirement better than multi-grade oils. Multi-grade oils are better suited to liquid cooled engines that can maintain more precise temperature control.

The fact that the engine is shutting down from low oil pressure as it warms up means the oil is not providing adequate lubrication at that point. Different engines respond differently due to the way manufacturing tolerances of the individual parts add and subtract so one engine may be better able to tolerate oil that's too thin better than another one with different internal tolerances.

The purpose of supplying oil to bearings is to prevent destructive metal to metal contact. Seems to me it would be easier and better just to change the oil instead of risking excessive bearing wear or engine failure from inadequate oil pressure.

 

[Onyrlef]

Once again, what viscosity oil are you using? Onan, Volkswagen and other manufacturers recommend single grade SAE 30 weight oil in their air cooled engines except in sub-freezing temperatures. Multi-grade oils like 5-30, 10-30, 15-40, etc. are thinner than 30 weight oil until they get up to full operating temperature and while this is preferable for the tight tolerances in modern water cooled engines they will will generate less cold oil pressure in air cooled engines.

From Page 6 of the Operating Manual, Engine Oil Recommendations:

"Single grade oil SAE 30 oil is preferable when temperatures are consistantly above freezing. Multigrade oils are better when large temperature variations (i.e. sub-freezing temperatures) are anticipated."

Thanks for nothing Lou, now I gotta go change my generator oil.

 

[MGH]

Thanks again, @Lou Schneider. That explanation helps. I will go ahead and change my oil to 30 weight, and see what happens. It's certainly cheaper/easier than ordering new control boards and tracing all the wiring - and of course it's what I'm supposed to have in the genset anyway.

This has been such a process. Early on I did suspect (and hope) that it was an oil pressure [sensing] issue. But then it seemed like it wasn't. And then several indications pointed to something wrong on the electrical side. And now back to oil. I'm always glad to learn new things. I'm looking forward to some semblance of a learning plateau at some point instead of a constant curve

 

[Mark_K5LXP]

Can't disagree with the premise of optimum viscosity vs ambient temp but is the oil sender in this thing really all that precise? I don't know if this unit has a pump or is splash lubricated but in either case would find it somewhat remarkable it can differentiate between 15-40 vs SAE30. I would've thought the sensor was more about oil present/not present. Changing to SAE30 will eliminate the variable but it would be interesting to learn just what the sensor is monitoring.

Mark B.
Albuquerque, NM

 

[MGH]

I did some more trials tonight. Part one was pretty much a repeat of yesterday. Part two showed some promise. But overall, it seems like this generator will start and run with light loads while cold, but has trouble with heavier loads when fully warmed up (oil pressure switch unplugged the whole time).

Part One:

• Changed the oil from 15W-40 to straight 30 as suggested by @Lou Schneider.
• Left oil pressure switch unplugged, started generator, it started and ran just fine, producing 120VAC in the coach.
• Let the generator run with no load for 30 minutes.
• After the 30 minutes, turned on rooftop air conditioner fans bit by bit. Front on low, then on high. Then also back on low, then on high. Let both run for just a minute.
• Turned front A/C off, then set back A/C to low cool.
• The ECCEM system monitored the current for just a few seconds, then I lost 120VAC power.
  • The generator continued to run
  • Something in the coach breaker and fuse box started buzzing – I think this is the changeover relay (Auto Transfer Switch), but I’m not sure why it’s buzzing.
• Exited the coach and turned the generator off from outside. Let cool for about two hours.

Part Two:

• After two hours, the generator was cool enough to touch, but still pretty warm.
• Left oil pressure switch unplugged, started generator, it started and ran just fine.
• After about 10 seconds, stopped the generator with the switch on the control board, plugged in the oil pressure switch, restarted, but it only ran for a few seconds before shutting off.
• Unplugged the oil pressure switch again, started generator, it started and ran just fine, producing 120VAC in the coach.
• Let the generator run for only about 5 minutes, then turned on both A/C fans as above.
• Turned front A/C off, then set back A/C to low cool.
• This time, the ECCEM system monitored the current for it’s typical ~1 minute, then the A/C compressor kicked on and produced cold air!
• I let the A/C run on low for a minute, then turned it up to “High Cool”. Generator and A/C both continued to run fine (total of ~8 minutes run time in Part Two).
• I turned on the TV (using 120VAC in the coach) and waited for another ~30 minutes. The generator and A/C continued running fine, along with the TV.
• At ~40 minutes run time in Part Two, I turned off the TV and A/C completely, and left the generator running with no load.
• After just one minute, with the generator running and still hot, turned the A/C back on; low fan, then high fan, then to low cool, but…
• This time, after the ECCEM system monitored the current for it’s typical ~1 minute, when the A/C compressor tried to kick on, I lost 120VAC power. As in Part One:
  • The generator continued to run
  • Something in the coach breaker and fuse box started buzzing.
• Turned the generator off using the switch on the dash panel so I could listed to the buzzing.
  • The buzzing at the breaker and fuse panel stopped, followed immediately by a click.
  • I’m still thinking this is the changeover relay, but not sure why it would do this.

One more piece of information: Throughout all of the above I did have the RV physically plugged in to a 30A shore power socket, but the breaker for that circuit was turned off. Not sure if just being physically plugged in could affect anything. Assuming I repeat this trial tomorrow, I will make sure to completely unplug from this socket.

Thank you to anyone who reads all this. I humbly ask for any other thoughts and suggestions.

 

[Old_Crow]

As a reminder, I have the exact same coach as you.

The transfer switch is located behind the power center box in the cabinet above the fridge. I bet that was your buzzing noise. First thing I would do is remove all A.C. power from the coach, take the faceplate off the power center box and tighten all the connections at the A.C. breakers. The first time we tried to run our a/c units after we bought the coach, they ran for a while and then there was a burning smell and all power was lost. Turned out to be that the wire from the ATS to the main breaker was loose at the breaker. The excess resistance melted the insulation on the wire and upped the current enough to trip the breaker. Thankfully, before it started a fire.

As for the way it's wired, the wire from the shore connector runs straight to the ATS, as does the power wire from the genny. Then a 3rd wire runs to the main breaker on the power center. If you're connected to shore power and you start the genny, the ATS will automatically switch to genny power without unhooking the shore cord.

Oh, and if it comes down to the ECC system (which I don't think it will at this point), I'll just toss this out for your information. They don't make parts for the old system anymore, but this is a plug and play replacement for the system.

 

[MGH]

The transfer switch is located behind the power center box in the cabinet above the fridge. I bet that was your buzzing noise.

Here's our power center. It all looks in good shape to my eyes. I see the wires from SHORE and GEN power coming in (the four wire nuts at the bottom), then going back behind the breakers. And there's the one wire coming from the transfer switch behind the breakers into the 30A main breaker. This wire is stranded aluminum while the others are all solid copper. Does that seem normal?

All connections were already nice and tight. I disconnected and reconnected the wire to the main breaker anyway. With the buzzing, are you thinking something might be going bad with the transfer switch? Would that explain the power going out under eletrical load on the generator after having come up to max temperature?

I remember you getting a Waiter system. I'd still like to do that someday to modernize, and avoid being stuck without HVAC unexpectedly.

Thanks.

 

[Old_Crow]

The slightly larger gauge wire going to the top 30A breaker was what fried in mine. It continued around the back of the power center to the ATS. I don't remember if mine is copper or aluminum, as it's been several years since this happened. Not even sure if I noticed at the time.
All of those screws on the breakers were at least a half-turn loose (the one on the main breaker was looser than that). I check them every couple of years now.

Yes, I was thinking that the buzzing might indicate that the ATS might be getting wonky. In my case, the ATS has been fine, but I had the genny just quit making power one day. After taking it to Onan I ended up buying a used Onan from Arizona RV Salvage. Due to a logistics failure on their part I ended up with a 7k generator to replace my 5k for basically 1/2 the price of a new 5k.