Power Equipment Forum banner

1 - 20 of 69 Posts

·
Registered
Joined
·
25 Posts
Discussion Starter #1
Hi everyone. I'm a new member here. I've been battling this problem for a customer for quite some time, and before I tear this engine apart, I wanted to get some input from any experts out there. Here is what's going on. I hope you are all up for this challenge! :tango_face_smile_bi

Without getting into the details of our business, we have a lot of experience with the Honda EU2000i generator. We literally have hundreds of customers who can operate this generator at the top of its 2000VA maximum output for hours on end, providing it doesn't run out of gas. 2000VA is of course 16.7A @120VAC. I've done a lot of research into the Honda, and using an aftermarket RPM meter, I know that the ECO mode idle is 3000RPM, the ECO mode off idle is 4300 RPM (which provides about 1600VA), and the full load RPM for 2000VA is 5000RPM. Under full load, every Honda EU2000i we've ever tested can provide about 115-120V at upwards to 16A without any problem, and do it continuously without skipping a beat. Typically, the voltage output is about 125VAC when unloaded.

Enter the problem generator owned by one of our customers. His name is Ron. Ron's generator will start off providing the full load amperage up to the 16.7A limit (say 16A for sake of testing), and its motor will reach and stabilize at the 5000RPM like all of the other Honda generators under the same test condition. Then, after about 3 to 4 minutes of operation, Ron's generator will start dropping in RPM. I know the throttle and its associated motor servo very well since we replaced Ron's carburetor with a brand new one a few weeks ago when this all started. The THROTTLE IS WIDE OPEN AND UP AGAINST ITS STOP for the entire time this RPM reductions starts and continues to take place. So, we know its not a control system issue. Ron's generator will then slowly drop in RPM, going as low as about 4400 RPM, and if the load is kept on, the output voltage of course will also start dropping. At no time is the load brought above the 2000VA limit (16.7A), so the generator never declares an overload (lights its LED). The voltage will eventually drop to about 98V if I keep the load up at about 15A. I don't have a precise load bank device, so my ability to adjust the load precisely as the voltage drops gets difficult since the load devices I'm using draw less current as the voltage drops.

Anyway, NO OTHER HONDA EU2000i THAT WE'VE EVER TESTED DOES THIS under the same test conditions. They all can hold their 5000 RPM rock solid, keep their output voltage in the 115-120V range, and keep their output current at or above 16A (to just below the 16.7A max limit).

So, over the past several weekends of working on this, I've eliminated the obvious causes of fuel, air, and spark. As mentioned above, the carburetor is brand new, the spark plug is new, the stator and rotor, and the various auxiliary windings were all tested per the service manual (voltage outputs at RPM and resistances). The fuel filter was changed, and the problem still occurs even when the air filter is removed (thus eliminating that). The valve clearances have already been checked and the exhaust valve was slightly adjusted (increased); it made absolutely no difference.

The only thing left is engine compression. I purchased a compression tester and did some side-by-side testing with Ron's Honda. I found that when it was hot, it had compressor down in the 35PSI range (40 when cold). A "good" Honda EU2000i that I tested alongside of it was in the 45PSI range when hot, and 50PSI when cold. The service manual of course states that the compression should be 71PSI when cold, but I have yet to measure a Honda with that much compression. Bottom line though, the "good" Honda with 50PSI when cold passed the above sustained load test without any issues.

So, at this point, I'm faced with going after the obvious causes of compression loss when hot: 1) Piston rings, and 2) valves.

Based upon the above, and the experience of those in this forum, what is the most likely cause here and does such a problem even ever happen with these seemingly bullet-proof Honda Engines? Since the design of the Honda EU2000i engine makes it difficult to inspect the valves since the head and cylinder body are a single piece (no removable head), I'll have to take out the piston to inspect the valves and the top of the cylinder head. I'm not a guru on re-lapping valves and removing and installing pistons with rings, but I can bring my engineering abilities to bear, learn what it takes, gather the right specialty tools, and do it. But before I do, I wanted to get some opinions and recommendations. Perhaps I'm overlooking some other cause that I should check first?

Any input would be appreciated. Thank you very much in advance for any advice.
 

·
Registered
Joined
·
155 Posts
Ok, so I have couple of questions. When it is running and losing rpm's during heavy load, do you notice any excess blow by from the crank case into the carb? I.E. loss of compression from a bad ring type thing. Second, do you notice any sort of miss or harsh running conditions during this issue? I.E. some sort of valve leakage?

Beyond those two items, you say you have eliminated the lack of fuel issue. What steps did you take to eliminate the possibility?

Have you been able to find the limit ampage the generator can handle before running into this issue. I.E. will it run fine under say a 10 amp load?

My thought here is that it could be an issue with the lower compression but if that is the case I would think you would be getting some extra blow by from the crank case.

Perhaps a leak down test might help you determine what you need to know.
 

·
Registered
Joined
·
25 Posts
Discussion Starter #3
Ok, so I have couple of questions. When it is running and losing rpm's during heavy load, do you notice any excess blow by from the crank case into the carb? I.E. loss of compression from a bad ring type thing. Second, do you notice any sort of miss or harsh running conditions during this issue? I.E. some sort of valve leakage?

Beyond those two items, you say you have eliminated the lack of fuel issue. What steps did you take to eliminate the possibility?

Have you been able to find the limit amperage the generator can handle before running into this issue. I.E. will it run fine under say a 10 amp load?

My thought here is that it could be an issue with the lower compression but if that is the case I would think you would be getting some extra blow by from the crank case.

Perhaps a leak down test might help you determine what you need to know.
Thank you very much, Handyman1957. My boss is a motorcycle engine builder/racer from decades gone by, and he has been stating the same things about the (unlikely) possibility of the valve and/or piston leakage. If I do not notice any blow-by/blow-back through the intake, then the intake valve can't be leaking. Also, if I don't notice anything abnormal coming out of the crankcase breathers, then I assume the rings aren't likely bad either. The exhaust valve might be the only one that would be hard to tell, but lots of soot, a clogged spark arrestor, and muffler carbon, and maybe some backfiring might be evident in that case. Honestly, I would have to say that I have NONE of the above symptoms. So, perhaps I am barking up the wrong tree as the boss is suggesting. I appreciate your making me think through this again.

What I do notice at the 3 minute point when the RPM begins to drop is a subtle change in the tone of the engine. Obviously, that is partly because of the RPM beginning to drop. I wouldn't say the engine is running "rough" at this point, but it certainly is no longer "smooth" and steady. The drop in RPM is gradual and slow, and it takes another 2 to 3 minutes to bottom out in the low 4000s, where it fluctuates slowly.

Like you, the boss also suggested a leakdown test instead of a compression test. I opted for the latter tester because it was cheaper to obtain. That may have been a mistake as well. Before tearing into anything I should probably consider doing this test somehow. I think I can rig something up with my refrigeration equipment. I'll go to 90PSI like the guy in the YouTube video did.

The generator can maintain about 14A of load without experiencing this drop in RPM after a few minutes of operation.

Lastly, the way I eliminated the fuel starvation cause was simply by the replacement of the carburetor and the fuel filter. I realize that there is a fuel pump, and high load means high fuel consumption, so the bowl could be falling behind. That might result in a leaner mixture, which does cause any engine to run hotter. I'm not sure what to do about this though. How can I inspect and/or service this fuel pump, or at least verify that the fuel flow is adequate for the high load condition?

Lastly, one symptom I forgot to mention, the RPM will go back to 5000RPM if I remove the high load, let the RPM drop back to say 3000 (ECO mode ON lowest speed) for a few minutes, then reapply the full load. I figured (and perhaps made the bad assumption) that the engine was cooling off during this time, thus allowing it to perform again when returning to high load for the couple minutes it seems to be able to handle. Maybe the fuel level in the bowl is recovering during this time instead and that is the cause?

Any input would be appreciated on how I could do a better job of verifying the maximum fuel flow. Thanks again.
 

·
Registered
Joined
·
155 Posts
Ahh, I believe you have answered your own problem right there. It now makes sense to me. It's very much likely your fuel pump is not able to keep up with the demand. The fact that you can relieve the load and after a few minutes be able to run it again at full load is the key indicator that your carb is leaning out. It sounds to me like the pump is just at the edge of failure and you are seeing this in the form of lack of full fuel pressure at full load. I sure there is a tool to see the pressure but the silly thing is, it's only $26 for a OEM fuel pump on ebay.

Genuine Honda 16700-ZT3-013 Fuel Pump Fits GXH50 GXH50U EU1000i EU2000i OEM | eBay

I would definitely replace the pump before I dig into the motor.

Of course a leak test wouldn't hurt if you could do it, but if you have to spend money to make that happen I would wait till the new pump is in and then tackle that job if the problem still exists.

Good luck.
 

·
Registered
Joined
·
224 Posts
Know nothing about Honda's, but agree with Handyman. Thinking about it, it runs under full load for three minutes, then acts up. Gotta be ignition or fuel. Compression testing, leak down, etc. look at physical metal components and head gasket. Find it hard to believe that Metal can stand the load for three minutes, then "sort of" break down, then recover, etc. ? $26 vs a teardown, I'd take that bet any day. Again, know nothing about Honda's, but if I replace a fuel pump on anything, I also replace the fuel lines and clean or at least verify the fuel tank outlet is clear. Partially obstructed fuel ine can act like a bad fuel pump.
 

·
Registered
Joined
·
25 Posts
Discussion Starter #6
Thank you Handyman and Exmar. I ordered an aftermarket fuel pump since I could get it in one day, and that turned out to be a mistake. It didn't fit properly. I tried it anyway, and it made no difference. I tested the existing pump, and checked all the fuel lines since I had the generator's skins completely removed today for better access to everything. I found no issues and the old pump appears to be working fine. I'll replace it anyway though.

Beyond the above, I ran a whole bunch of tests today over the course of many hours. Given what I observed, I'm once again having a tough time attributing fuel starvation to the RPM symptoms. One would think that if the fuel bowl were falling behind at high load, it would eventually empty and I would then notice more dramatic changes in RPM (drop-outs and surges). That never happens. The RPM drops 10 revs at a time (per the digital meter), slowly and gradually, starting from 5000, and the motor seems to be running smoothly throughout. With the skins off today and the motor fully exposed, I was able to watch and listen to the motor more closely during this RPM loss. It really doesn't seem to be running any rougher. During the first couple minutes, the RPM can attain 5000, and the throttle isn't quite wide open and I can see the servo motor regulating it. Then, slowly the throttle has to be opened more and more, eventually ending up pinned against the stop. It is at that point that the control system has obviously run out of dynamic range, and then the RPM starts it slow and steady drop. After about 5 more minutes, the RPM seems to settle at around 4400RPM, and with the load at about 14.3A. For comparison, last week I tested about 6 or 7 Honda EU2000i generators at an RV rally and was able to verify that they all held 5000 RPM and 16A+ indefinitely (5-10 minutes in the tests I ran). I therefore know these Honda's can do this. Why this one in particular can't is still a mystery.

I'll order the OEM fuel pump, but I don't expect it to resolve the issue. The gas tank was already cleaned and the fuel filter already replaced (as part of this debug process which started weeks ago). I'm now planning on purchasing another generator for our customer to perhaps be able to swap and keep this one for further analysis to the root cause.
 

·
Registered
Joined
·
155 Posts
Well, my thought process on the fuel pump is this. As the motor is requiring more fuel the pump is pumping but slowing down on delivery but not stopping. Therefore, as the bowl gets lower the motor starts slowing down thus requiring more fuel till it can't get anymore from the throttle.

Perhaps this is fuzzy logic but it's the only thing that makes sense. If this were a metal fatigue issue, I.E. rings or valves then how would it be able to recover without completely cooling the engine back down first. If the engine runs perfect even when slowing down then it leads me to believe that it must be a fuel issue. I've never heard of a valve or rings being able to recover in such a small period of time. Especially without showing some sort of running issue like excessive blow by from the crank case or popping or spitting as was the case for me when I had a leaky exhaust valve or simply never having enough power.

I will be looking forward to what happens when you do replace the fuel pump.

One more dumb question, when running into this issue have you tested to see if there is a vacuum in the fuel tank? I.E. the pressure release mechanism is plugged and causing a vacuum in the tank thus making it harder for the pump to pull fuel?

Next time you try a test, pull the fuel cap off when it starts to rpm down and see if there is a vacuum.
 

·
Registered
Joined
·
25 Posts
Discussion Starter #9
Thanks again, guys. Not only did I remove the gas cap during the "problem" yesterday as a test, I took it all apart to clean it. I was partly curious how it worked anyway, and noticed that it really doesn't pass that much air when in the "ON" position. In any event, the cap was not the cause.

Although I am still tore, I do like the rationale of your fuel starvation theory, Handyman. I ordered the OEM fuel pump last night, but now I have to wait for it to ship cross-country. I wish there was a way to test the fuel flow as the cause without having to wait.

The fuel line routing of the Honda EU2000i does end up requiring the pump, but there may be a workaround for testing purposes. The bottom of the fuel tank is slightly below, but almost level with the fuel bowl of the carburetor about 8-10" away. The fuel filter is integral with the fuel tank exit fitting. The fuel line then goes down, makes a 180 deg turn and connects to a small petcock at the back of the on/off ignition switch. This rotary switch turns off/on the ignition and turns off/on the fuel at the same time. The fuel line then exits the petcock and goes straight up and into the input side of the fuel pump after a 45-deg turn. The inlet of the fuel pump is slightly below the level of the tank exit, so gravity should at least bring fuel to that point. The outlet of the fuel pump then goes pretty much straight across the side of the generator/engine (horizontally with maybe a few degrees of incline) into the carburetor about 6" away, after a few more turns. I had traced the entire thing yesterday when I was inspecting hoses for blockage, and although I saw that the hoses were pristine on the inside, there were opportunities for hoses to kink. If the fuel pump were marginal, then I could certainly see why it might fall behind.

So, as a test I was thinking that I could temporarily mounted or hold the fuel tank well above the height of the carburetor, effectively doing gravity feed straight into the carburetor without the pump (or petcock). I'd could keep the cap loose enough to avoid any issues with back pressure. I can't imagine that the float and valve in the fuel bowl would require any more pressure than this to operate. What do you think?
 

·
Registered
Joined
·
25 Posts
Discussion Starter #10
No go with new OEM fuel pump and leak test passed!

UPDATE:

I received the OEM fuel pump today and also received a cheap leakdown tester a couple days ago. I had picked up an almost brand new Honda EU2000i on Monday from a pawn shop. It was pretty much out-of-the-box.

The new Honda passed the load duration test fine, holding 5000 RPM for over 10 minutes without any fluctuation. I ran a leakdown test on it and it wasn't that great. Probably because it isn't broken in yet.

I then installed the new OEM fuel pump on the problematic Honda and ran the load test again. There was no improvement in the load duration test as I expected. The RPM held at 5000 for about 3 minutes, then started its slow decline. I ran the leak down test afterwards and to my surprise it was 9-12%, which is considered quite low. I could not hear any pressurized air escaping on the old Honda during the leakdown test like I could on the new Honda. The old Honda was as tight as a drum, although it had cooled about 5 minutes by the time I got everything apart to conduct the leakdown test.

So, I'm back to where I was. At this point, given all that I have done, I really feel like I've eliminated fuel, spark, air, and goodness maybe now even compression! What else could it be?

One other observation that I have with the problematic Honda is the heat of the engine air exhaust and the heat of the main (muffler) exhaust during the load test. The problematic Honda seem to MUCH run hotter than any other Honda I've ever tested. Substantially more. There is good air flow from the fan, and everything is obviously intact, free flowing, and clean as a whistle since I've had this disassembled almost completely several times. I cannot explain what could cause it to run so hot. This may be related to the problem.

Where do I go from here? Thanks in advance.
 

·
Registered
Joined
·
25 Posts
Discussion Starter #11
TEST:

2 of my last replies to this post have been withheld for moderator review. I'm not sure why. This post is short as a test.

I do have tests results from the OEM fuel pump and leakdown compression test. I will report on those if this post seems to make it through.
 

·
Registered
Joined
·
25 Posts
Discussion Starter #12
Okay. It looks like it's working. I'll try to keep this brief since I think when I write a lot, it triggers the withholding for moderator review.

I received the new OEM fuel pump and a leakdown compression tester this week. I also purchased an almost new Honda EU2000i for the customer.

New Honda Test Results: Passes load endurance test with flying colors. Maintained over 16A for over 10 minutes. Held RPM solid at 5000. Leakdown compression test was actually quite bad since I don't think its broken in yet! I could actually hear the compressed air escaping out of the exhaust and intake at TDC.

Problematic Honda Further Test Results: New fuel pump made absolutely no difference in the load endurance test results. It still did what it always does maintained the 16A output and 5000RPM for about 3 minutes, then started its slow decline thereafter. A Leakdown compression test results were phenomenal! 9-12%. I could not hear any compressed air escaping out anywhere on this old Honda at TDC!

One thing I do notice is the problematic Honda really does seem to have very hot exhaust cooling air and very hot muffler exhaust. This may be related to the problem.

So, I really now feel like I have done a thorough job of eliminating fuel, spark, air, and even compression! What else could be the cause of this mysterious loss of power and RPM after 3 minutes of full load operation?
 

·
Registered
Joined
·
155 Posts
This is a strange beast to say the least.

I'm going to throw one more idea out at you. You say it has a very hot exhaust?

Is it possible that the muffler is perhaps somewhat plugged, I.E. the spark arrester?

A bad exhaust valve would not cause a hot muffler, but lack of proper flow out the muffler would.

Kinda like having a clogged catalytic converter.

And a over heated motor would lose power as it got hotter and as it cooled regain that power.

Just a thought.
 

·
Registered
Joined
·
25 Posts
Discussion Starter #14
Thanks again for the suggestion. Long ago in the debug process, thinking along the same lines, I did clean and then try running without the spark arrestor. I was going to even try to run without the muffler, but because removing the spark arrestor didn't even make the slightest improvement, I didn't want to bother the neighbors with the extreme noise.

Reading more online, I am now wondering if there is a lubrication problem. I know oil is reaching the cam and the top of the valves since whenever I adjusted their clearances - which I did many times as as experiments - they were always well oiled. I'm not sure what's going on in and around the piston though. I'm delivering the new Honda to the customer tomorrow, and will run a side-by-side test to see what the temperatures actually read out with my laser IR temp gun. I'll be keeping the old Honda for further study.

Last thought, I watched a YouTube video about a week ago of a person who tore down a Honda and had found cracks in the single-piece, cylinder/head body. I'm wondering if something isn't going on around the intake, resulting in intake air leakage when the engine heats up, driving the mixture more lean, thus heating it up further. It recovers within a minute of running at idle from whatever is going wrong, and it will then run at 5000 RPM again, albeit for a shorter period of time (since it's already hot).
 

·
Registered
Joined
·
142 Posts
Hi all,

This is a generator with a included inverter unit, this inverter takes power from the engine through the alternator and after rectifying the AC power produced, converts it to AC 60 Hz 120 V up to 2000 VA, using a set of MOSFETS in a bridge configuration.
If there is a lack of cooling in said Mosfets they can start in a thermal run down condition, failing to commutate and taking more current for the same load, increasing the heating in the dissipators.
The change in the sound tone may be for a excessive load for the engine as it were supplying more than 2000 VA, lowering the voltage produced the current lowers too, and the MOSFETS then can supply this lower load.

This is just one cause to produce a fail in the inverter, failing capacitors or MOSFETS may alter the correct operation too.
To determine this possibility of failure you can measure the alternator output current in any of the AC output wires during the critical 3 minutes period at full load, or replace the inverter asm. and try again.

Regards
 

·
Registered
Joined
·
155 Posts
The only problem with your idea is that the OP stated this.

Then, after about 3 to 4 minutes of operation, Ron's generator will start dropping in RPM. I know the throttle and its associated motor servo very well since we replaced Ron's carburetor with a brand new one a few weeks ago when this all started. The THROTTLE IS WIDE OPEN AND UP AGAINST ITS STOP for the entire time this RPM reductions starts and continues to take place. So, we know its not a control system issue. Ron's generator will then slowly drop in RPM, going as low as about 4400 RPM, and if the load is kept on, the output voltage of course will also start dropping.
I think it would be safe to assume at this point that it's not an inverter issue as it does try to get more RPM's when the motor starts to drop in power. The only time he see's voltage drop is when the RPM's get to low and it's at full stop on the throttle.
 

·
Registered
Joined
·
142 Posts
Yes, 3 or 4 minutes at full load may be the time needed to increase the transistors temperature at a point where they are not more stable…….May be…….

I think that it is like driving, and slowly applying brakes. The engine will not withstand that load and decrease RPMs even maintaining a wide open throttle .

It is important to note that this is a 3 phase generator with 3 non fused lines, connected directly to the inverter. Its output is 2000 VA at 120 volts, the input must be a 10% higher, so the generator output is about 2200 VA trough 3 lines (3 phase generator) : Red, white, blue wires. Assuming that the inverter works directly with the generator line voltage, the line current would be:

2200 VA/ 120 V = 18.3 A for single phase, but this is a 3 phase gen, so the line current will be:
18.3 A / 1.73 (3 Sq root) = 10.5 A per line.

This at full resistive load, during the first 3 minutes, then to compensate the extra heat due to the inverter failure, this current will increase and the engine overloaded will be unable to maintain 5000 RPM at this torque demand and will reduce RPM, this reduce voltage output and this the current up to a point where there is a balanced condition. More or less something like that.
 

·
Registered
Joined
·
155 Posts
Ahhh, now it's much clearer. This makes sense. Thank you for the understanding.

This is the part where I am a bit clueless. The mechanical makes sense to me but I don't have the understanding for the high end electronics.

I did not realize that the inverter would actually require more power than the generator could actually supply. But after your explanation I can see how this could be the case.

I think he has pretty much gone over everything else that makes sense. The extra heat at the exhaust could simply be from the generator working so hard to keep up with this extra load.
 

·
Registered
Joined
·
25 Posts
Discussion Starter #20
Good morning, gentlemen. Sorry for the delay in responding. I'm only able to work on this project during my "working" weekends.

I intend to run Osviur's test this weekend. Thank you for the suggestion. I concur that if the load on the 3-phase alternator feeding the inverter goes up, so does the load on the engine. That in turn could cause a slow decrease in RPM if the alternator load is climbing due to a problem with the inverter drawing too much current internally due to a variety of issues (e.g. IGBT 3-phase H-Bridge cross-conduction). I'm going to put a clamp-on ammeter on one or more of the 3-phase alternator output wires feeding the inverter, and simultaneous monitor the other things I have been monitoring (output voltage, current, and RPM), and then reproduce the problem. If the current exiting the 3-phase alternator's stator goes up as the generator heats up, then Osviur's theory that the inverter may be developing an issue at higher temps is likely true. If the output from the alternator's stator stays steady during the "working" 3-minutes and then starts dropping with the RPM, then that would prove it is not the inverter overloading the alternator due to some internal inverter issue.

Hopefully I'll have results to report by tomorrow. If the test fails to prove that the inverter is the cause, then the darn engine is coming apart next!
 
1 - 20 of 69 Posts
Top