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Ziller Tech
MikeCB;48502 wrote:
So I'm brainstorming here, maybe others can help me debunk or confirm my theory as a possible cause.....

A while back, Kohler had an issue where the flywheel fan was drawing air across the internal regulator breather ports, that it was causing a low pressure situation and issues to follow. While I am unfortunately no longer on site to test, I noticed that Generac has the baffle positioned in a manner that it would be drawing air downward and potentially across the air intake on the firewall. I am wondering if this could cause a similar situation, theoretically causing a "low pressure" scenario inside the airbox.

Next time I come across a unit that is actively hunting, I am going to take a piece of cardboard and lay it horizontally across the top of the flywheel fan baffle (in an attempt to prevent its draw from interfering with the engine intake) and see if it has any effect on the hunting.


I've often wondered the same thing. I've blocked them briefly with my hand but didn't notice a change really. The fuel pin/air filter change seems to be the most effective. I even see some that run fine, and when we do maintenance with a brand new filter they start to surge. No noticeable difference in the filter being plugged with orange goo, just something different about the media itself. Old filter fixes it right away?
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MikeCB
Chris Flagg;48503 wrote:
I've often wondered the same thing. I've blocked them briefly with my hand but didn't notice a change really. The fuel pin/air filter change seems to be the most effective. I even see some that run fine, and when we do maintenance with a brand new filter they start to surge. No noticeable difference in the filter being plugged with orange goo, just something different about the media itself. Old filter fixes it right away?
I wish I had thought if this while I was on-site. I'm going to try and completely block it next time I get one and see what happens though. Previous tech swapped the filter which apparently did have some abnormalities. I personally didn't see it though. Same as before though, lifting that lid a little bit made it go away.

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Ziller Tech
The filters I've swapped have not looked any different (maybe slightly different color media) but they've fixed it after trying a few along with the fuel pin swap.
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MikeCB
I'm just not convinced the air filter is even the problem. I can make the problem go away by just turning the unit off and on a few times until it stops without doing anything else. Due to the intermittent nature I've experienced, I'm afraid replacing filters repeatedly is just giving a bunch of false positives. I may try one if these vented lids. I figure it'll either work or it won't. If it doesn't I'll move on to something else.

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redman
Have you tried slowly shutting off, the shut off valve before the Generator and see if motor settles down and stop's surging ?
Mike
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Ziller Tech
MikeCB;48516 wrote:
I'm just not convinced the air filter is even the problem. I can make the problem go away by just turning the unit off and on a few times until it stops without doing anything else. Due to the intermittent nature I've experienced, I'm afraid replacing filters repeatedly is just giving a bunch of false positives. I may try one if these vented lids. I figure it'll either work or it won't. If it doesn't I'll move on to something else.

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I've seen units with the vented hoods still surge with old or new filters. A filter swap sometimes works, and I've installed the old filter just to check and make sure the problem came back. It's certainly an A/F mixture problem, just not sure where or what causes it... Fuel pin seems to work most of the time.
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MEC
Bulletin just came out today regarding this.
It's listed on Genservice in the news section.


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kershner
I hope it gets posted to the Ziller site.


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MikeCB
MEC;48623 wrote:
Bulletin just came out today regarding this.
It's listed on Genservice in the news section.


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Thanks for pointing that out.

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MacL
If it's the bulletin I read, I find it ridiculous.

It says "it's normal, it's the nature of the throttle linkage design" (no, it isn't)
It says "it won't do it in automatic under load" (yes, it will)
It says "Running the unit full speed with no load is not intended" (uhhh, 12 minute exercise)
It says "Therefore set it to low speed exercise and the problem is solved" (see #2)

Further, it attacks all attempts to mitigate it by changing filters or drilling holes:

"added holes will harm the air/fuel ratio" (uh it's naturally aspirated engine)
"the holes we put on later models are due to different parameters unique to that model"
"An aftermarket air filter will make the unit unsafe"
State your problem, not your diagnosis.
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Pville
MacL;48694 wrote:
If it's the bulletin I read, I find it ridiculous.

It says "it's normal, it's the nature of the throttle linkage design" (no, it isn't)
It says "it won't do it in automatic under load" (yes, it will)
It says "Running the unit full speed with no load is not intended" (uhhh, 12 minute exercise)
It says "Therefore set it to low speed exercise and the problem is solved" (see #2)

Further, it attacks all attempts to mitigate it by changing filters or drilling holes:

"added holes will harm the air/fuel ratio" (uh it's naturally aspirated engine)
"the holes we put on later models are due to different parameters unique to that model"
"An aftermarket air filter will make the unit unsafe"


I think this was on the last page of that bulletin:

"We have not succeeded in answering all of your problems.
The answers we have found only serve to raise a whole set
of new questions. In some ways we feel we are as confused
as ever, but we believe we are confused on a higher level and
about more important things." :rolleyes:
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MEC
Lol, that's what I got from it as well.


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restosud
i feel sorry for generac dealers that have to face complaining customers with tsb's like this:(
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ohmslaw
Allowing more fuel with a bigger primary orifice cures the issue but probably changes the EPA certification. I think we just need to get the proper drill bit and fix it ourselves .
Tim
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MikeCB
ohmslaw;48722 wrote:
Allowing more fuel with a bigger primary orifice cures the issue but probably changes the EPA certification. I think we just need to get the proper drill bit and fix it ourselves .
Tim
Maybe I read it wrong, but my take from the TSB wasn't necessarily that more fuel was needed. It was just that the primary orffice was full open already and the stepper would occasionally bump the secondary, allowing for a brief air rush. If the primary was a little larger, the stepper could just close it a little more allowing the same amount of fuel, but preventing that accidental bump.

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ohmslaw
MikeCB;48734 wrote:
Maybe I read it wrong, but my take from the TSB wasn't necessarily that more fuel was needed. It was just that the primary orffice was full open already and the stepper would occasionally bump the secondary, allowing for a brief air rush. If the primary was a little larger, the stepper could just close it a little more allowing the same amount of fuel, but preventing that accidental bump.

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More fuel through the primary would allow the motor to reach the proper RPM with out bumping the secondary. That should cure the issue. I am not an engineer at Generac so this is an Educated guess. :D
Tim
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MikeCB
ohmslaw;48735 wrote:
More fuel through the primary would allow the motor to reach the proper RPM with out bumping the secondary. That should cure the issue. I am not an engineer at Generac so this is an Educated guess. :D
Tim
Neither am I. But at times, don't you feel that we should be? Lmao

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MacL
restosud;48720 wrote:
i feel sorry for generac dealers that have to face complaining customers with tsb's like this:(


This situation just continues....any action would admit a mistake...so it just continues. Maybe we need robots for engineers.
State your problem, not your diagnosis.
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MacL
A fix on the manufacturing end would be to redesign the engine cooling air inlet deflector so that air enters only from the bottom or rear, but not the top. The deflector's main intake is at the top which robs what would be combustion air and diverts it into the flywheel.
State your problem, not your diagnosis.
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DaveN
Does this apply to 16kw units too? I am having a surging issue, mostly once the ac is running.

Mine does indeed seem to have an issue with getting enough air through the intake/filter box. Box cracked or open, no surging, box closed surging. The filter had no effect on the surging.

Generac says a bad batch of air filters is out there and they have too much flame retardant on them. They are sending a new one.

I verified that taking the filter out and closing the box also stopped the surging. I am leaving the filter in and the box cracked until the new one arrives.
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Ron Goldstein Rongold
Chris Flagg;n47794 wrote:


It is a Generac part number. They come standard on all 999cc 7000 series units. Generac does not advise changing them just to change and they are not meant to be an 'upgrade'. I would ALWAYS advise calling tech support before doing anything with these units.


I just came across this thread and I would like to let everyone involved know that I just had a #7043 22kw generator installed last week, and I went out and removed the air filter cover and there are no holes in it. There are a couple of baffles to direct the air, but no holes. The generator was produced on 4/16/2018 so it's new enough to have the cover with the holes, but it doesn't. So far, no problem with it, but it has only been loaded down once and exercised once.

One thing that I noticed, but I don't know if it would make a difference----The air flow is from top to bottom through the air filter. In my 45 years as an ASE certified master auto technician, I have NEVER SEEN a vehicle that has air flow through the air filter in this direction---They all flow from bottom to top.

RON
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Birken Vogt
I am also a former auto mechanic and thinking back, I can't think of another instance where a flat panel air filter feeds straight into a venturi like this. Flat panels usually seem to feed into a long hose before the venturi, and "direct fed" venturis if you will, usually are fed through a round air filter that surrounds them on all sides. Maybe for more even air flow?
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