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Discussion Starter #1
I just purchased a new Honda EU7000is a few months ago. I just pulled it out Monday of this week due to an ice storm knocking out power and have been running it non-stop for the past 100 hours. I've changed the oil and checked/cleaned the air filter and pre-filter per the manual. When I checked the air filter and pre-filter at the 20 hour mark I noticed that the oil in the pre-filter was soot black. I cleaned out the sponge pre-filter using acetone (manual specifies using either soapy water or a high flash point solvent) which got most of the black sooty oil out of the sponge pre-filter. I let it dry then re-oiled with some engine oil and squeezed out the excess oil. The pleated paper filter also had some oily soot on it but it was only on about half of the filter. I don't have a replacement pleated filter or I would have changed it (manual says to replace at 300 hrs.). I just changed the oil at 100 hours and found more sooty black stuff in the oil pre-filter. I clean the pre-filter again and continued running. I'm not forecasted to have power back to my home for another 5 to 7 days so I'd really like to figure out what's going on. I've got a new filters on order that will be in on Tuesday of next week.

My theory is that the black soot is coming from the evap canister which would mean that it's charcoal. I wiped the inside of the intake tube with a clean rag and found a thin dry film of the black soot.

Question: What is happening? Where is the black sooty stuff coming from? How do I fix it? See below for a pic of the sooty oil I cleaned out of the pre-filter.
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Thanks,
Nathan Ashley
 

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Nathan,
Sorry to hear of your dilemma, mainly the ice storm damage etc. You certainly are working the genny hard, but that is what the Hondas are made for though. Call your local Honda dealer and see what they suggest. However, I'm wondering if, one, you have the oil overfilled. Maybe run it slightly below the full mark. Secondly, what type of oil are you using? I'm suggesting that you go to a motorsports shop and pick up some synthetic motorcycle oil. I really like AMSOIL small engine oil, but you need a solution now. It's possible that the oil in the genny is frothing/foaming/burning due to inferior quality or overfilling thus being recycled through the charcoal cannister and then into the intake causing the sooty mess. I personally don't think that it's a big issue, but it's just not quite right. Let us know how it goes, Dutchy
 

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....I meant to say that possibly the oily vapours are drawn into the charcoal cannister and then into the intake causing the sooty mess... Dutchy
 

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Discussion Starter #4 (Edited)
Thanks for the reply, Dutchy. I'm using Mobil 1 10w-30. The oil over-fill could make sense but I don't think the crank crank case is vented into the purge canister. I'll be calling a dealer tomorrow to talk with them and will post here if I figure out something. Do you think overfilling the tank would cause fuel to fill the evap canister and cause the problem i'm seeing? I just stopped it to check the oil level and pulled the tubes off the evap canister as well. I noticed that the evap canister "purge tube" (the tube that goes from the evap canister to the air cleaner) is lined with the soot/charcoal.

Here's a picture of the pleated filter that contains the sooty stuff.
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And a closer look.
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I swiped my finger inside the intake and found a thin dry film of the sooty stuff.
8352
 

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where is the gen set running ???
is it in an open area?
or a quite box?
make sure you clean the exhaust screen!!
it is often over looked on the honda gens! as well as on the other honda power equipment.
some even remove the screen if they are not using it on job sites.
it is a spark arrest-or.

how full of fuel are you running in the gas tank?
do not over fill the tank!

that is one of the things that can trash an evap unit.
makes for an ultra rich unit.

get a new paper air filter on it asap.
a corked air filter can trash a good engine fast!
and can cause smoking due to low air on the intake.
think running a gen with the choke on all the way smoky!
yea these are fuel injected so no choke.

use super light oil on the pre filter.
we use the k&n spray oil..

make sure the crank case vent is working right...
it could have a bad flapper on it.

these are a basic gx 390 engine.. easy to work on.

last thing is there could be an issue with the fuel pump
as low pressure... no mist can be rich on a FI engine.
check the fuel screens.

and make sure you did not get 2 stroke fuel in the gen or some diesel!!
yea it does happen if some one is not watching the cans!
we get that on the construction sites with all kinds of fuels on site.
some other contractors do not mark the cans right..

if you think it might be bad fuel drain it in full and fill up with fresh gasoline.

on to the oil
was the oil over full when you went to check it?
that can indicate an over fueling and running down in to the crankcase.
we get that on the carb units..
but not yet on the eu7000is units.
 

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Discussion Starter #6
It's running in an open area in the middle of the backyard.

I know I'm not overfilling the gas tank. I always fill it to the red ring in the tank. I pulled the charge tube off the evap canister and blew some air thru the tube and found that the tube terminates about 2 or 3 inches above the max fill ring. I checked the drain pipe and air tube for the evap canister as well and didn't see any evidence that fuel had drained through the evap canister.

I've never seen any exhaust smoke (black or white) when running the generator. It's running very smooth and I've never heard it cough or sputter.

I checked during the last oil change to see if I could smell any gas in the oil. I couldn't smell any gas and the oil level was the same as when I filled it.

I'm trying to find a dealer in the area that still has power. I'm in the Oklahoma City area. Can someone recommend a dealer in this area?
 

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Just a quick point on oil fill. Almost all Honda small engines have a dipstick, but were easily identified as full when the oil is up to the top of the threads on the filler neck. These EU7000s are not designed to be filled to the top of the filler tube. You must add a premeasured amount of oil or use the Dipstick. Did you accidentally overfill it?

As @iowagold suggested definitely check your exhaust screen.

For comparison purposes, I have about 30 hours on my Eu7000 and my air filters are clean with no sign of build up at all.
 

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Discussion Starter #8 (Edited)
drmerdp, both the owners manual and the shop manual (shown below) specify that the oil is to be filled "...to the top of the oil filler neck...". Where are you seeing that Honda specifies differently? I would expect to see oil in the intake but am only seeing this black dry residue that has virtually no smell to it and seems to me to be charcoal. Only the oiled pre-filter is black and oily but the pleated filter just has the black powdery stuff on it. I would also expect to see foaming of the oil if it was overfilled but it never looks foamy. All of my used oil only comes out a little darker than when it went in.
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The stand-alone honda manual for the OHV GX390 engine specifies the same oil fill level. See below.

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I checked the exhaust spark arrester and it's clean (not sooty).

I'm refilling to the upper level red ring, as is indicated in the manual shown below. The tank vent tube is about 1 inch above the upper fill level. The vent tube is connected to the top side of the evap canister. I've removed this tube and found no evidence of fuel in the evap canister and no evidence that liquid fuel has passed thru the evap canister and out the bottom drain hose of the canister.
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I went to a local dealer this morning to pick up a new pre-filter and pleated filter. I talked to them about this and they said that it could be charcoal from the evap canister, engine running to rich, or bad injector. They're swamped due to the ice storm and no one would be able to take a look at my generator for a while. I don't see how an engine running too rich would cause the intake air filter to be filled with a black soot only on the outside of the filter. The engine side of the filter is spotless and dry. There are no signs that the fuel mixture is the culprit since It's running very smooth and the exhaust is spotless.

I just installed the new filters, cleaned the inside of the intake box, and changed the oil. I filled the oil to about 1/4 inch below the top of the fill neck. It seems that the charcoal/soot stuff is no longer getting into the intake. I can tell because I flipped the filter end-for-end after the 50 hour oil change and haven't seen any more charcoal/sooty stuff on the clean end of the filter. I'll go back out to check the new filter in a couple of hours.

I need to get some more oil drain plug crush washers. I've had to re-tighten the plug the last two oil changes because of some small drips. The shop manual specifies 17 ft.-lb. for the drain plug but I've found that re-use of the washer will require a few more ft.-lbs. to prevent leaks.

Sigh...this ice storm is kicking my but.
 

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we use gasoline to clean the pre filter or use dawn in hot water.
the other chems could cause the plastic in the pre filter to break down..

check the crank case vent tube and see if the carbon is from there?
a q tip in the hose will show that stuff..

yea clean the exhaust screen and see if it is corked!
 

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it could be an issue with the sensors.
if it is detecting super cold etc it could over fuel.
at the honda service centers they have a computer to look at the lambda on the computer as live.
a basic honda gen set only scan tool.
 

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make sure all of the sensors are plugged in right!!
un seat then re seat them carefully!
 

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Discussion Starter #12
Just checked the new pleated filter and new pre-filter and the cleaner case after a couple hours of run time. The pleated filter is spotless but the intake side of the pre-filter is starting to get black again nearest the intake. I removed the breather tube from the valve cover and only found a light coating of clean motor oil. I also removed the silencer cover and found the same film of clean oil on the inside. I then noticed that the crank case/valve cover vent tube only vents on the engine side of the air cleaner. This means that if this issue was due to oil overfill I would see evidence of oil on the engine side of the air filter, but it's spotless. At this point, I think the only explanation would be the evap canister. The evap canister is the only thing, other than outside air, that enters the air cleaner case on the intake side. I located the hole in the air cleaner case where fuel vapors from the evap canister enter. It's a very small hole that's shown in the picture below. I used a q-tip (thanks iowagold) to probe the area right around the small hole and found a heavy buildup of the charcoal. This is the same stuff that I found when I pulled off the end of the purge tube at the evap end. At this point, I'm convinced this issue is caused by charcoal from the evap canister. Somehow, charcoal from the evap canister seems to be getting blown or sucked into the intake. Any ideas on why this would be happening and how to fix it? I've checked all tubes going to and coming from the evap canister and found no blockage.

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8357
 

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replace the canister!
and the hoses!
it could have a bad canister that was dropped!
all of the charcoal can be busted up in side!
 

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drmerdp, both the owners manual and the shop manual (shown below) specify that the oil is to be filled "...to the top of the oil filler neck...". Where are you seeing that Honda specifies differently? I would expect to see oil in the intake but am only seeing this black dry residue that has virtually no smell to it and seems to me to be charcoal. Only the oiled pre-filter is black and oily but the pleated filter just has the black powdery stuff on it. I would also expect to see foaming of the oil if it was overfilled but it never looks foamy. All of my used oil only comes out a little darker than when it went in.
View attachment 8353

The stand-alone honda manual for the OHV GX390 engine specifies the same oil fill level. See below.

View attachment 8355

I checked the exhaust spark arrester and it's clean (not sooty).

I'm refilling to the upper level red ring, as is indicated in the manual shown below. The tank vent tube is about 1 inch above the upper fill level. The vent tube is connected to the top side of the evap canister. I've removed this tube and found no evidence of fuel in the evap canister and no evidence that liquid fuel has passed thru the evap canister and out the bottom drain hose of the canister.
View attachment 8354


I went to a local dealer this morning to pick up a new pre-filter and pleated filter. I talked to them about this and they said that it could be charcoal from the evap canister, engine running to rich, or bad injector. They're swamped due to the ice storm and no one would be able to take a look at my generator for a while. I don't see how an engine running too rich would cause the intake air filter to be filled with a black soot only on the outside of the filter. The engine side of the filter is spotless and dry. There are no signs that the fuel mixture is the culprit since It's running very smooth and the exhaust is spotless.

I just installed the new filters, cleaned the inside of the intake box, and changed the oil. I filled the oil to about 1/4 inch below the top of the fill neck. It seems that the charcoal/soot stuff is no longer getting into the intake. I can tell because I flipped the filter end-for-end after the 50 hour oil change and haven't seen any more charcoal/sooty stuff on the clean end of the filter. I'll go back out to check the new filter in a couple of hours.

I need to get some more oil drain plug crush washers. I've had to re-tighten the plug the last two oil changes because of some small drips. The shop manual specifies 17 ft.-lb. for the drain plug but I've found that re-use of the washer will require a few more ft.-lbs. to prevent leaks.

Sigh...this ice storm is kicking my but.

Brain fart, yup totally right. I pictured a GXV oil fill for some reason.

I’m glad too see you have a shop manual, Honda does a great job with their manuals.

It certainly seems that the evap system is the culprit... Is the canister filled with liquid gas? If so, why. Something might be going on at the tank.
 

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Discussion Starter #15 (Edited)
replace the canister!
and the hoses!
it could have a bad canister that was dropped!
all of the charcoal can be busted up in side!
I pulled the evap canister yesterday evening and all 4 hoses attached to it just to double check that there is not blockage in one of the hoses. No blockage found. I shook the evap canister and it sounded like a course loose sand was inside. I'm not sure if the charcoal inside is supposed to be loose or not. Thoughts?

Brain fart, yup totally right. I pictured a GXV oil fill for some reason.

I’m glad too see you have a shop manual, Honda does a great job with their manuals.

It certainly seems that the evap system is the culprit... Is the canister filled with liquid gas? If so, why. Something might be going on at the tank.
The evap canister was dry, best I could tell, and I didn't see any signs of liquid gasoline having been in the lines. The canister sounded dry when I shook it ( no clumpy/cloddy sounds).

I'm thinking I should probably get a new canister. Should be covered under warranty but only if I can get it in to a dealer to have them process it and that's not going to happen for another week. Looks like this cost is on me.

Edit: Just found this diagram online for how the evap canister works in the system.
8358
 

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Nice diagram and explanation. I wonder how difficult/easy it would be to disconnect either the charge tube prior to the canister (preferred) or the purge tube. If the charge tube could be disconnected you could keep an eye on how much liquid gas is actually discharged if you could collect it somehow. (although you say it seems dry)
If the purge tube is disconnected/rerouted try to do so prior to entering the filter box. Although this method could cause the canister to become overfilled with fuel because it is not being evacuated.
Try this just for the time being, and after your local dealer slows done to normal have them check the system out. I think that it would be a good idea to have the canister checked out and replaced though. I don't think that the charcoal is meant to be loose inside of it. At least the charcoal dust is stopped by the filter........ Dutchy
 

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I like the idea of a makeshift catch can on the evap purge hose. You can use a small inline fuel filter with a transparent housing.
 

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Discussion Starter #18
Alright, after studying the gas evap system I think I've discovered what is causing the charcoal to be sucked into the air cleaner. So, we all know that it's not the best idea to refuel the generator while running and the manual clearly states this. There's lots of info in the manual about fire/explosion risk if refueling while the engine is running and/or hot. And, I know there's an increased risk but I chose to ignore it (I don't refuel any other power equipment or vehicle while it's running so not sure why I thought it was ok in this situation). Anyway, I think there is another reason to not refuel while running and this reason is NOT stated in the manual. I think that if you remove the gas cap while the generator is running, the engine will quickly suck the air thru the gas tank vent tube, thru the evap canister, thru the purge tube and into the air cleaner! I've depicted this situation shown in red in the diagram below. I won't be able to confirm this is what is happening until I refuel (with engine off) tonight but I'll keep you posted. I just finished cleaning the charcoal out of the pre-filter and hopefully for the last time. By the way, if you ever need to clean charcoal dust out of a filter, acetone or soap & water do not work. They just will not suspend the particles to allow them to be removed from the filter. What does work is dousing the filter in an oil bath, squeezing it out, and repeating a few more times. This got it perfectly clean.
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Man, I hope this solves the problem.
 

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the epa reason they have to have a canister is the fuel dances in the fuel tank!
so if they want to burn the tank vapor it need to have a catch can that will store the droplets that get sucked in the hose to get it back to vapor.
that way the mixture is not too upset.
and with electronic lambda fuel injection it adjusts the injected mixture to keep it from running too rich.

you can old school this with a vented fuel tank cap (eu6500 cap) and plug all of the canister ports.
 

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Discussion Starter #20
Just want to follow up with the resolution to my problem. We got power back after 13 days so I took the generator to a local dealer to have them take a look at it. They determined it was indeed a faulty evap canister allowing charcoal to be sucked into the air filter. They replaced the evap canister and even put in a new air filter all under warranty.
 
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