Problems when RVing in extreme heat

[Brad Buchanan]

And I had the genny vapor lock problem again while at Big Creek Camp. I think that is happening in the stupid carburetor, mounted inside where very hot. The fuel pump is mounted underneath, still hot there too, but probably not as hot as dead center inside the genny.

I am tempted to remove this Onan QG 5500 genny also, and use my portable EFI gennies that also can do 240 VAC at 30 amps (7.2KW continuous) for charging my motorcycle.

IMAO, Onans are pure junk with mostly 1960's technology.

-Don- Sac Pass, NV

You should get one of those harbor freight chinese top of the line gens.

The rest of us will continue to use our industry standard Cummins/Owens gensets.

 

[Brad Buchanan]

I would like to hear more about that mod.

If there is vapor lock in the very hot carb, does pumping cooler gas into it help that much?

The time several days ago, it was when I used the genny for an hour or so and two hours after it being off it would not start. Another hour or so later, it started right up.

I never had my genny die after it once started, regardless of how long or how much load. Just will not start when very hot.

-Don- Sac Pass, NV

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Vapor lock happens in fuel lines, not carbs.

 

[DonTom]

Vapor lock happens in fuel lines, not carbs.

It can happen anywhere there is fuel before the engine, except for the gas tank.

I will now see what AI says:

"Yes, vapor lock frequently occurs in carburetors, particularly in older vehicles or those with low-pressure fuel systems. It happens when excessive heat causes liquid fuel to boil and turn into vapor before it reaches the carburetor or within the carburetor itself, disrupting the engine's fuel supply. "

BTW, I just now got back from a hike. it is 91 degrees in here. I tried to run the genny so I could turn on the A/C for a few minutes but the stupid Onan 2022 1960's designed QG 5500 generator is vapor locked, will not start. The genny is in the SW side of this motorhome with the sun shining on it this warm afternoon.

BTW, did I mention how, IMAO, new Onans are junk?

But I am getting by fine with my $30.00 HFT fan with the windows open. And now to heat my dinner with my MW oven using my 4KW inverter that I installed, since I cannot use the junky Onan

-Don- Sac Pass, NV

 

[bigbAZ]

My generator is diesel so no worries about vapor lock, but I did have an "Inverter over-temp" shutdown issue in hot weather. What I did was first remove the rear wheels and punched 3 large holes above the mud flap so more air could get to the intake, which is located right behind the tires, then I got a high CFM 7" pusher fan from Summit Racing and attached it onto the generator air intake, blowing directly on the inverter. I also made a weather cover for the 3 holes that I can attach in seconds with wing nuts.

Have not had any issues with over temp since I did that. Maybe something like that could help with your vapor lock?

 

[Derby6]

It can happen anywhere there is fuel before the engine, except for the gas tank.

I will now see what AI says:

"Yes, vapor lock frequently occurs in carburetors, particularly in older vehicles or those with low-pressure fuel systems. It happens when excessive heat causes liquid fuel to boil and turn into vapor before it reaches the carburetor or within the carburetor itself, disrupting the engine's fuel supply. "

BTW, I just now got back from a hike. it is 91 degrees in here. I tried to run the genny so I could turn on the A/C for a few minutes but the stupid Onan 2022 1960's designed QG 5500 generator is vapor locked, will not start. The genny is in the SW side of this motorhome with the sun shining on it this warm afternoon.

BTW, did I mention how, IMAO, new Onans are junk?

But I am getting by fine with my $30.00 HFT fan with the windows open. And now to heat my dinner with my MW oven using my 4KW inverter that I installed, since I cannot use the junky Onan

-Don- Sac Pass, NV

And AI is always right. Good grief……..

 

[DonTom]

Maybe something like that could help with your vapor lock?

Hard to say what will help when the genny, not used for more than 8 hours, and then for only a few minutes, will not start because of heat just from the sun.

Now at 1930 hrs I will check inside the genny and see how hot it is inside and then try to start. So don't go anywhere until I get done checking in a few minutes . . . .

Not what I expected! I did wonder if a hot day could cause VL when the genny has not been running for hours--and with no engine heat blowing on it. Perhaps not even possible!

The real problem is I get a normal indication inside the RV that the genny is cranking. I just now tried to start from the genny itself, same indication but the starter is NOT spinning at all. No crank, nothing other than the normal cranking indication. No starter noise, no click, but I do hear a weak sound of something in there, perhaps the fuel pump turning on when I press the button in on the genny.

Perhaps it is just the way the starter is lined up at the time, is there a way for me to spin it a fraction of an inch or whatever? But no click makes me think a relay. But I never checked for the click before this. But I do hear a weak something in there, perhaps the fuel pump turning on. Whatever it is, it is very faint.

So this has nothing to do with vapor lock and makes me wonder if I had this same problem before when I was blaming it on VL when it would not start.

But I find it interesting when I checked for heat inside, the hottest thing in there was the carburetor fuel bowl,. Warmer than the rest of the genny, Perhaps because it is not on the big heat sink case and is normal. Don't know.

But my problem now is no cranking.

BTW, did I mention that IMAO, these newer Onans are junk, just like the older ones?

-Don- Sac Pass, NV

 

[DonTom]

And AI is always right. Good grief……..

It is always right when I agree with it! And that is around 90%, so far.

-Don- Sac Pass, NV

 

[DonTom]

You should get one of those harbor freight chinese top of the line gens.

For my Y2K RV, I got a pair of these EFI gennies and they work so perfectly it caused me to hate the Onan junk with the 1960's design. Even my 1971 BMW motorcycle has CV carbs--no need for an elevation adjustment unlike my 2021 Onan in this motorhome.

Just having a carb is ancient technology, IMAO.

But I have no doubt even the HFT gennies will be more reliable than Onans. The HFT gennies have good reviews.

If I need to remove the Onan starter motor (which also crapped out in my Y2k Onan), it means I must remove the complete Onan. If I do, it will never go back in. I will use the portable gennies even if I have to remove them from the motorhome to use.

-Don- Sac Pass, NV

 

[DonTom]

My genny started fine this morning. And I didn't do anything at the genny.

How does a genny starter problem become heat related?

I am beginning to believe that I never had a vapor lock problem with this Onan, just a temperature sensitive starter or solenoid. But how is such possible?

This genny has always started fine on cool mornings. But often not when warm.

And from inside the RV, it gives a normal cranking indication (blinking LED) regardless if the starter engages or not. But it becomes solid if the genny starts, like it did this morning but not yesterday.

All my problems have been when warm/hot, but I never had a reason to expect it was a problem with the starter until . . . (see message 86 above).

I don't think this is just simply coincidental that the starter will nor always engage when warm, but always will when cooler--but I am not 100% sure of anything.

Anybody have any guesses of what my real Onan QG5500 genny problem is?

-Don- Sac Pass, NV

 

[RV_Lee122]

Its the fuel line, do what the guy did in the video, specific model doesnt matter. Hes in south florida, if it stopped vapor lock for him it'll stop it for you. Or keep the generator door out of the direct sun, keep it shaded somehow.

 

[DonTom]

Its the fuel line, do what the guy did in the video, specific model doesnt matter. Hes in south florida, if it stopped vapor lock for him it'll stop it for you. Or keep the generator door out of the direct sun, keep it shaded somehow.

Please read message 86. I discovered my Onan problem has nothing to do with vapor lock.

-Don- Sac Pass, NV

 

[Brad Buchanan]

Hard to say what will help when the genny, not used for more than 8 hours, and then for only a few minutes, will not start because of heat just from the sun.

Now at 1930 hrs I will check inside the genny and see how hot it is inside and then try to start. So don't go anywhere until I get done checking in a few minutes . . . .

Not what I expected! I did wonder if a hot day could cause VL when the genny has not been running for hours--and with no engine heat blowing on it. Perhaps not even possible!

The real problem is I get a normal indication inside the RV that the genny is cranking. I just now tried to start from the genny itself, same indication but the starter is NOT spinning at all. No crank, nothing other than the normal cranking indication. No starter noise, no click, but I do hear a weak sound of something in there, perhaps the fuel pump turning on when I press the button in on the genny.

Perhaps it is just the way the starter is lined up at the time, is there a way for me to spin it a fraction of an inch or whatever? But no click makes me think a relay. But I never checked for the click before this. But I do hear a weak something in there, perhaps the fuel pump turning on. Whatever it is, it is very faint.

So this has nothing to do with vapor lock and makes me wonder if I had this same problem before when I was blaming it on VL when it would not start.

But I find it interesting when I checked for heat inside, the hottest thing in there was the carburetor fuel bowl,. Warmer than the rest of the genny, Perhaps because it is not on the big heat sink case and is normal. Don't know.

But my problem now is no cranking.

BTW, did I mention that IMAO, these newer Onans are junk, just like the older ones?

-Don- Sac Pass, NV

Keyboard warriors would be better served hiring real mechanics.

 

[DonTom]

Keyboard warriors would be better served hiring real mechanics.

Perhaps some.

But this should be fairly easy for me to figure out. But not in this heat, I will wait until that side is in the shade. instead of turning the RV around. No big hurry to fix.

500 watts of solar is keeping my batteries charged to full and I can run the MW oven and such from my added 300 AH lith battery that does not effect anything stock, which is now separate 400 AH lith batteries (700 AH total). I do not really need the genny at all for anything on these bright sunny days --other than for the A/C when it gets too hot inside here. But nice shade just outside the door, so still not a big issue.

The starter relay/stater solenoid could be at two different places in the QG5500, depending on when made. It is either behind the compartment that holds the start switch on the genny (which I hope for) or mounted on the starter. That is where I am going to start my troubleshooting. If I cannot get it to fail, I will run wires from various points to the outside so they can be checked when it does fail--if possible (relay wires where I can get to them without removing the genny).

I doubt if the professionals can troubleshoot this intermittent issue any better than I can unless its such a common problem they have seen it many times before. But I doubt this is a common problem. Only 247 hours total on the genny since new and had this issue many genny hours ago, thinking it was something else. No way to tell from inside, because even when working, I do not hear the starter from inside, and the led indicator shows as cranking even when it is not.

From now on, when it doesn't start, I will be checking the genny from outside.

-Don- Sac Pass, NV

 

[DonTom]

It is another hot afternoon,, I ran the genny for a couple of hours with both A/C units on as I was inside doing other things. I shut down the genny and went to dump my trash and take a short walk around the perimeter. I was back in around ten minutes and by then the genny should be a lot hotter than it was yesterday.

It started right up, within a few seconds being as hot as ever.

So I am now wondering if it has only been a coincidence that it would not start on hot days and the real problem is just an intermittent starter or whatever.

Or a combination of both, intermittent starter as well as vapor lock.

I was only able to confirm a starter problem one time so far-that was yesterday.

But at least now I know what to check for when it will not start, and to ignore the indication from inside for when starting.

-Don- Sac Pass, NV

 

[DonTom]

I tried the genny again in another hour. Another surprise. It would NOT start, so I went outside to the genny, and it cranks fine but still wouldn't start. I tried several more times, and it finally started and has been running fine for the last half hour.

Ran very rough for a few seconds and then at a perfect steady RPM and has been fine since.

IOW, it was most likely flooded, not vapor-locked.

IMAO, my carbphobia is very well justified.

-Don- Sac Pass, NV

 

[Mark_K5LXP]

my carbphobia is very well justified

Something to be said for "no computer".

Like with the propane fill issue you could eliminate a number of causes with even basic troubleshooting. Instead you reach your nominally plausible conclusion and that's the final word until proven otherwise. I had a hard starting Cummins and instead of blaming vapor lock I went out there and isolated the problem - missing choke linkage parts. If you think it's flooded, not choked enough, 'starter alignment' or whatever there are basic checks to prove or disprove them. I frankly think the cummins design has outlived it's usefulness but there's something to be said for a mature design and number produced. Many many thousands of these things start and run perfectly every day. You're a smart guy, figure it out. Then report your findings for others to learn from. For extra credit come up with a better mousetrap so it doesn't happen again.

Mark B.
Albuquerque, NM

 

[DonTom]

Something to be said for "no computer".

Some people believe that such as the Airhead Club (For the old air cooled BMW motorcycles such as my 1971 BMW). Their motto is "simple by choice".

However, if there is a choice, I will never buy a carb anything, period. I have a very bad case of Carbphobia with more reasons than I could list here.

One thing for sure is that my Onan QG5500 Genny in this rig has more than one problem. Intermittent starter, flooding, and perhaps vapor lock. The first two are well proven, IMO. I cannot say for 100% sure that I have ever experienced vapor lock in this motorhome. I have made the stupid mistake with assumptions too many times. Perhaps I will never learn not to assume things just because they seem obvious.

That my genny was not cranking was not even anything I thought about until it was proven with my own eyes and ears right at the genny.

My reasons for believing it was flooded yesterday: Cranked fast, started after many long attempts (not good for the starter!). Very black exhaust smoke for around five to ten seconds when it finally started. And then ran perfectly for as long as I wanted. I had both A/C units on, very hot day and it was running perfectly fine after I finally got it started. And I ran it for at least an hour with no issues. And it was hot here then. That does NOT sound like a vapor lock problem to me, just a flooded carb.

Flooding was a common problem on my Onan 4K as well. What I did to "fix" it was to put a manual gas line valve in the fuel line before the carb. When it flooded, I turned the valve off and started it until it burnt out the excessive gasoline and then opened the valve. That worked every time. I will probably need to do the same with this QG5500. The flooded carb burns out the gas very fast when no new gas is going into the carb. And it also dries out the spark plug. So it then starts MUCH faster and is a lot easier on the starter,

But I have no clue for now what is causing my starter to sometimes not crank. I have no idea why it would crank normally in the morning as well as start right up. I will check what I can when I get this rig home. Hopefully it is not the starter itself, or the type with the solenoid mounted on the starter. That means the entire genny must be removed from the motorhome. I dislike Onans 1960's technology so much that if I once take it out, I will most likely never put it back in and just use my portable EFI inverter gennies that have nothing but advantages (except for one) over the Onan, including more power (7.2 KW continuous, 9,600 watts peak-- and does 240 VAC for charging up my bike at 6.4 KW.

The only disadvantage is that I will have to set up the gennies one time at each stop. They have wireless remotes for starting. And they have three ways to start. The remote, press a button on the genny, or if the small internal Lifepo4 internal battery is discharged, use the pull thingy.

This motorhome has a large door for the genny. I think my inverter gennies could fit in there if the Onan is removed.

-Don- Sac Pass, NV

 

[Firstime RVer]

Tried starting my Cummins Onan today after sitting for 3 months and it started right up. I swear by adding Stabil to my fuel !!
Safe travels and all the best.

 

[DonTom]

Tried starting my Cummins Onan today after sitting for 3 months and it started right up. I swear by adding Stabil to my fuel!!

I have used gasoline more than a year old countless times--with no additives and no issues.

Recent example.

What I find interesting is I have an unused bottle of Sta-Bil. It says right on the bottle "will keep gasoline fresh for up to one year".

That makes me believe that the gasoline lasts longer than the Sta-Bil.

So perhaps your gasoline is keeping your Sta-Bill fresh.

-Don- Border Inn RV Park, Baker, NV (& Utah: casino in Nevada, their restaurant and gas station is in Utah).

 

[Ex-Calif]

Tried starting my Cummins Onan today after sitting for 3 months and it started right up. I swear by adding Stabil to my fuel !!
Safe travels and all the best.

Prepping for a trip. Drug my Cabella's genny out of the shed after 9 months and it started instantly. The battery wasn't even flat. Crazy...