351M, genny will not stay running while driving

[tamrick]

Well, I most certainly can fault someone. This was one of my first questions to the dealer, "Can I run the genny underway"? They answered "of course". If they had answered otherwise, I wouldn't have bought one and would have just gone straight to the inverter in the truck bed. Then, when having trouble, the dealer (who could not recreate the issue and sent me to Onan) said, "working fine, you should be good to go" (crapped out less than 1 mile from the dealer). Went to Onan, they also told me "should work great" and could not recreate the issue.. Again, crapped out within 10 mins of picking it up.

If it's not supposed to work, well, then, say it's not for use while driving. That's a reasonable position, but I would have saved 4-5K, no need for a genny if I can't use it for the thing I want/need it for. I'd find another way to do it and no harm, no foul. But don't tell me "yes, that will work" if either you don't know or it, in fact, isn't supposed to work that way.

Thing I've wondered now for awhile, while I'm sure you're right, most people don't do this, there have to be SOME people who do, right? Even if you just run it for the 30 mins before you get to the campsite to cool the inside of the rig, I'd just think that this problem would be much more widespread, especially given that there's just almost no way it's going to work in the stock configuration because of the pump lift issue; that should effect anyone trying to do this. I've wondered this for awhile, why am I the only one? Is it just that I do it more? Worse roads in my area? Bigger hills? It just seems like there has to be something at play in my specific configuration that's causing this problem. I'd love it if some other 351M owners with a genny would try to run it for a few hours pulling and see if it craps out for them. Is it me, or is it everyone just not many people running into it?

I run mine every time we pull to keep the fridge going to save on LP. And to cool the rig before we arrive. It has only stopped twice so far. The first time, I have no idea why. I did not have my app open to watch the geny since I didn't think it would cut off. Just this past weekend, on a 100 mile trip one way, it stopped 15 minutes into the trip. (I always have the app open to the geny on/off button so I know if it goes off.) This time I believe it went off because I had to slam on the brakes at 40mph for idiot driver that turned into my lane. About 5 minutes after that, I noticed the geny was off but I don't know exactly when it shut off. It was on before the hard braking. Restarted it and it never went off. We traveled I20 east to Terrell, TX. I20 east of Dallas has horrendous bumps! I thought the shackles were going to break. So the trip was extremely rough and bouncy for about 30 minutes and the geny didn't shut off. Based soley on this last event, I thinking my hard braking caused the fuel pick up in the tank to suck air or the weight of the fuel pushing forward forced too much fuel into the geny. Fuel tank indicated full but I am pretty sure it was down about 5 gallons. Who knows. It hasn't occurred enough to guess at why it shuts off. Hope you get yours figured out.

[offtohavasu]

I looked at my tailpipe with 6 hours on the unit and still looks like new, so your soot build up is interesting. Hopefully the fuel regulator fixes that.

Also, I'm in the boat of running while driving. It was going to be warm up in Julian when we left, so when we were on the highway the wife pulled out her phone and started the generator and then fired up the A/Cs. BTW she make me laugh. She's not very technical, so as we're driving she reads me each message. "It says it's priming" "It says it's starting" "It says it's running."

[Redapple63]

Don't think you have a fuel delivery problem. Think it is a bad ground or other electrical connection that becomes intermittent when going over bumps.

[Overtaxed]

Don't think you have a fuel delivery problem. Think it is a bad ground or other electrical connection that becomes intermittent when going over bumps.

I thought that to, but I really don't think so anymore. Puting the additional fuel pump back by the tank I went maybe 3-4K miles without issue. Without it, I couldn't make it to the highway 3 miles away (there's a big hill on the way there) without losing it. I'm pretty sure it's fuel delivery, it's much, much better with the pump than it was without it.

It could be other things too, no question, but I'm pretty sure it's a fuel issue at the heart of it. Haven't pulled yet since putting the regulator in, but hopefully that's the end of it, first pressure too low, then perhaps pressure too high/flooding, now hopefully "just right".

[huntindog]

I thought that to, but I really don't think so anymore. Puting the additional fuel pump back by the tank I went maybe 3-4K miles without issue. Without it, I couldn't make it to the highway 3 miles away (there's a big hill on the way there) without losing it. I'm pretty sure it's fuel delivery, it's much, much better with the pump than it was without it.

It could be other things too, no question, but I'm pretty sure it's a fuel issue at the heart of it. Haven't pulled yet since putting the regulator in, but hopefully that's the end of it, first pressure too low, then perhaps pressure too high/flooding, now hopefully "just right".

I feel good about your chances. According the the Onan manuals, you absolutly had a fuel pressure problem. When they give a warning in bold print "FUEL LINE PRESSURE MUST NEVER EXCEED 1-1/2 PSI UNDER ANY CIRCUMSTANCES." And you have a 4 psi pump on it..... That IS an issue. Of course with all things mechanical, there can be more than one problem.... But you have now elminated a KNOWN problem.

[Overtaxed]

I feel good about your chances. According the the Onan manuals, you absolutly had a fuel pressure problem. When they give a warning in bold print "FUEL LINE PRESSURE MUST NEVER EXCEED 1-1/2 PSI UNDER ANY CIRCUMSTANCES." And you have a 4 psi pump on it..... That IS an issue. Of course with all things mechanical, there can be more than one problem.... But you have now elminated a KNOWN problem.

Yeah, I agree, it was certainly "wrong" before, and, given the symptoms, especially puking carbon out the pipe all over the power pole, it was clearly running rich. That could be a lot of causes, but, since we KNOW it was too much fuel pressure, there's a good chance that was at least exacerbating the issue. Also, it was working great for months after I put the new fuel pump in. What changed? It got CRAZY hot. Which reduces the amount of O2 in the air, causing it to run even richer, perhaps to the point of stalling out. It all makes sense and logically follows that this could be what I'm running into. We will see next time I pull it.

You know the thing that really kills me about this? OK, yes, I should have seen that line in the manual. But I specifically asked them, at the Onan (not RV, the Onan) repair place when I took it in, "What kind of pump should I get". And they never mentioned that it was critical to keep the pressure that low. There are basically no electric fuel pumps that have pressure that low from the factory, so.. How about "you need to put a fuel pump and regulator in" instead of "Just get any low pressure pump, that should do it". <sigh> Really annoying, the service experience has just been, well.. Atrocious all the way around. If Onan called and said "we can fix it, needs a pump, but you're gonna have to pay for it", I would have jumped at it. Nope, you fix it. Which is basically what I got from the dealer too. I'm the LEAST equipped to fix it people, you are experts, you have every tool on earth, and you have the manufacturer backing you. I have Amazon and a screwdriver. Why the heck am I fixing this?!

[huntindog]

Yeah, I agree, it was certainly "wrong" before, and, given the symptoms, especially puking carbon out the pipe all over the power pole, it was clearly running rich. That could be a lot of causes, but, since we KNOW it was too much fuel pressure, there's a good chance that was at least exacerbating the issue. Also, it was working great for months after I put the new fuel pump in. What changed? It got CRAZY hot. Which reduces the amount of O2 in the air, causing it to run even richer, perhaps to the point of stalling out. It all makes sense and logically follows that this could be what I'm running into. We will see next time I pull it.

You know the thing that really kills me about this? OK, yes, I should have seen that line in the manual. But I specifically asked them, at the Onan (not RV, the Onan) repair place when I took it in, "What kind of pump should I get". And they never mentioned that it was critical to keep the pressure that low. There are basically no electric fuel pumps that have pressure that low from the factory, so.. How about "you need to put a fuel pump and regulator in" instead of "Just get any low pressure pump, that should do it". <sigh> Really annoying, the service experience has just been, well.. Atrocious all the way around. If Onan called and said "we can fix it, needs a pump, but you're gonna have to pay for it", I would have jumped at it. Nope, you fix it. Which is basically what I got from the dealer too. I'm the LEAST equipped to fix it people, you are experts, you have every tool on earth, and you have the manufacturer backing you. I have Amazon and a screwdriver. Why the heck am I fixing this?!

I agree completely! Unfortunantly I have experienced so much poor work, that I long ago resolved to do as much of my own work as possible.... It seemed like every time I paid someone to do something, I was disappointed.... This has worked well for a long time, and saved me a ton of cash.... But I can see that in the not too distant future, I will be unable to do everything I used to...... It sucks getting old, but it beats the alternative.

[Overtaxed]

I agree completely! Unfortunantly I have experienced so much poor work, that I long ago resolved to do as much of my own work as possible.... It seemed like every time I paid someone to do something, I was disappointed.... This has worked well for a long time, and saved me a ton of cash.... But I can see that in the not too distant future, I will be unable to do everything I used to...... It sucks getting old, but it beats the alternative.

I'm so jealous of people who find really good service facilities, BigTruckRV, on Youtube, seems to be able to find them like a dog sniffing out a t-bone, he's had so much work done it makes my head hurt. Every time he goes in and the guys are like EXPERTS, I'm just sitting here thinking "where does he find these people". Suspension experts, truck engine experts, RV experts, he should start a service to sniff them out in your area and connect you to them.

I hear you though man, I hear you. I'd love to have a network of service people who I thought would do a good job at a reasonable price. Shoot, even a crazy price, if they did good work, I'd use them. I can't find any who are willing to call me back. Warranty work, like what I had on my genny, they have to call me back, but even that, it took weeks to get into the RV dealer (who didn't fix anything) and then weeks to get into Onan (each time, and neither time did they fix anything). So annoying.

[Overtaxed]

Well, the genny gremlins are back. I went a few 1000 miles without a problem, but, the last camping trip before the summer came (we don't camp in the summer), pulling home same problem. <Sigh>

I've had it with this generator, it's reliability is just the pits for me. Anyway, kind of good news, this time it's repeatable when not towing. It'll crap out in 10-15 mins no matter what I'm doing. Change the fuel pump (on the genny) and the filters today, no dice (same symptoms). Pulled the soot plug out and nothing notable there. My next step is to rig a "T" in the fuel line and see if the pressure is dropping when it starts to die. Certainly sounds like it's starving for gas, it'll start to run a little rough, surge once or twice, then shut down. It's actually a bit faster than a normal "out of gas" small engine, but I attribute that to the electronics pulling the plug when the engine starts to surge.

Same error code, 36. It's got 2 new fuel pumps on it now (the pusher pump and the one on the genny itself. I'm just at a loss. It's definitely heat related, so I suppose it could be something inside the engine (coil/magneto heating up and losing spark). Or it could be a vapor lock on the fuel line, it's SO hot in there when it's running surprises me it works at all.

Anyway, if anyone has some good ideas, I'm all ears. I'm honestly considering ditching it and getting an EFI model instead, I've had it with this thing, and I really don't know if it's the genny or something in the RV (bad fuel line that fails sporadically, vapor lock, issue with the EVAP system). And, the fun part of that, Onan will remote feed it fuel and, if it runs, they call it good. The RV dealer will say "anything generator, it's Onan's problem". Love the finger pointing.

In the interim, I did do a cool mod that others may like. I added another transfer switch by the generator, and ran wire up to the pin box for a 2nd generator inlet in my truck bed. I have a little 4000 watt inverter generator that I can put in the bed of the truck, and that thing will run no matter what the road looks like, it's a champ. 500 dollar generator, runs like a top underway. 5000 dollar generator, yeah, not so much.

[offtohavasu]

That's a major bummer that happened. I was hoping you had it figured out.

Ours did it in the way to Havasu, but it was 114 outside so attributed it to vapor lock and was just going to add a lift pump.

I don't remember the pump you added. I know in diesels it had to be low psi high flow.

I know you were going to measure psi, but maybe try testing vacuum in the line. Should be pretty low with the list pump, but if it's high maybe a collapsed fuel line?

Have tried running it solely on pushing the fuel eliminating the front pump?

I know we're slinging stuff to see what sticks at this point.