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Black smoke and low mpg

8K views 79 replies 17 participants last post by  boy_christian 
#1 ·
My 2003 Wing had gone through some problems. At first FI lighted up while I was going for 1,000 miles trip. The code is 26 but i had to finish the trip so I forced her to go. At the end of journey, she was hard to accelerate, Also a lot of black smoke when open throttle, and it went to 14 mpg.

After that, I replaced the ECM with a brand new one, replaced the spark plugs, spray DCS carbjet through intake and sparkplugs, put liquid engine cleaner to the tanks, clean TPS, everything that can be done to restore her back.

But then, all ok except black smoke still came out if I widely open throttle (though the smoke much lesser than before) and fuel consumption is 21 mpg.

Is there any step I missed to do?

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#2 · (Edited)
Put a fuel pressure regulator on the end of the left fuel rail and check pressure. You may have a bad fuel pressure regulator. When first powered on it should be around 50psi. At about 2K rpm it should be around 41psi. You'll need the right adapters to connect the gage to the fuel rail, and access to it will require taking stuff apart, as it is in a hard location to access. You may have to pull the whole left side fairing panel.



http://www.pbase.com/fredharmon/fuelpressure










If you don't put something on the vacuum line to the fuel pressure regulator to restrict vacuum pressure, the gage may be hard to read due to vacuum line fluctuations, and it will look like the below photo. I had to add a restrictor to the vacuum line going to the regulator to get these measurement photos. Basically, all you are trying to see is if the fuel pressure fluctuates with vacuum pressure properly.

 
#3 · (Edited)
By the way, if you don't have the right adapter or a fuel pressure regulator gage, it might make more sense just to replace the fuel pressure regulator and see if that fixes your problem, since the gages and adapters may cost more than a new regulator.

Its also about the same amount of work to replace the regulator as it is to take the measurements.

REGULATOR, PRESSURE
16740-MCA-003
$58.29
 
#7 ·
As I am not completely sure of the regulator set up. If there is a vacuum line to the regulator and you take it off, there should be no fuel dripping out. This is an indication of a blown regulator diaphragm. The vacuum line will suck the fuel through the regulator.
 
#20 ·
If the black smoke is coming out of only one pipe, I would suspect a leaking injector. If the black smoke is both sides, it has to be an overfueling condition common to both sides. (it could be injectors leaking on both banks but the odds are against it) As previously mentioned, fuel pressure regulator is most likely suspect. Overfueling the engine is detrimental to a lot of expensive parts (Cat Converter, O2 sensors, Engine, etc.) DO NOT let this situation go on too long !!!!!
 
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#22 ·
Over on the Rune board, this condition: Big Black Smoke - has traditionally been caused by a failed TPS. Cleaning it didn't make any difference. It was DOA. Honda wanted to put complete throttle bodies on some of the earlier ones that failed while under warrantee, and didn't offer a TPS separately for that bike.


Since the GL1800's share so much in common with the Runes, would it be possible that the TPS is also causing this bike's symptoms rather than it's fuel regulator???????????????????????????????


...just thinking out loud...
 
#26 ·
Don't forget that several sensors share a common ground. I damaged that connector when putting the top shelter back on. Results was very rich running to the point that it would die at idle. Plugs would be wet with gas and black in only a few minutes. No codes were set and no other indications of what was wrong. Fixed the bad connector and all was well.
Tread about it here:

http://gl1800riders.com/forums/5-gl1800-tech-board/269362-sudden-bad-idle-help-needed.html
 
#31 ·
I've got a spare motor with (known good when removed a couple years ago) fuel regulator and throttle body. Would be happy to ship you parts to change out rather than buying new just for testing... (use em and send em back or keep em and send me a few bucks for gas...)

Let me know if you're interested, and your mechanic doesn't mind working with used parts.

Leaving the country in a few days though, so let me know....

:thumbup:
 
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#33 ·
I've got a spare motor with (known good when removed a couple years ago) fuel regulator and throttle body. Would be happy to ship you parts to change out rather than buying new just for testing... (use em and send em back or keep em and send me a few bucks for gas...)

Let me know if you're interested, and your mechanic doesn't mind working with used parts.

Leaving the country in a few days though, so let me know....

[emoji106]
thanks so much for the offer. really appreciate it. I am from Jakarta Indonesia, used part is valuable here and we buy lots lots of it from junk yard in Singapore so people here doesn't mind at all working with it.
I will try to replace that regulator first, and if it doesn't improve then I will accept your offer.
Thanks bro

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#32 ·
We have had about several reports of bikes running real rich and belching black smoke on this forum over the years, and all the ones I remember were traced back to a faulty fuel regulator.

You might also check for a rats nest in the air box, but I really doubt that could cause black smoke. Something is causing raw fuel to go into the engine. The only things I can think that would make a bike run that rich would be a faulty regulator or stuck open fuel injectors.
 
#35 ·
Go back to the thread posted above and if you don't want to read the whole thing, most of the answers are in post #20 and #22. There are pictures there as well.
Short story is that while putting things back together the tank vent hose fell out of its proper place, when I put the wiring harness back in place it would not fit because the hose was below it. This pinched the ground wire splice and caused the problem. Shelter off, all OK, shelter on, pinched, ran rich. I was able to duplicate it by pinching the splice with just my fingers with the shelter off and it would nearly kill the engine.

Not saying that is your problem, but it caused similar symptoms. This splice affects inputs from 3 different sensors all at the same time. Didn't cause a fault code but confused the ECM enough to cause the problem.

Small wires and low voltages are particularly sensitive to bad connections caused by dirt or corrosion. Any change of resistance in a circuit can really mess things up.

Good luck and let us know what you find.
 
#41 ·
still coming out when I open throttle.
so my conclusion is not the regulator.

some people suggested to replace throttle body, and some others suggested me to totally take out all engine component and do tune up (blue print).

I will be going for 400 miles trip this coming weekend with this wing. After the trip I think I will be doing the 2nd option

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#49 · (Edited)
According to my Clymer Honda manual, the baro outputs about 2.9-3v at sea level. Voltage drops as elevation increases. (and by mere tenths of a volt per every 500 ft.) Is this not accurate, Techdude? It seems like this problem could get expensive with part swapping if sensors and systems are not tested properly. Hey, it's not my money though! For all we know, the return line to the tank is pinched. I don't recall if that was mentioned or not.
I've also seen MAP sensors on cars go SERIOUSLY out of spec causing rich exhaust, sputtering and the like. Yet, the computer would not recognize the fault and not turn on the MIL. Less likely with a MC?
 
#50 ·
I don't like throwing parts at a problem either, that's why I said the fuel pressure should be checked before swapping the regulator... If the OP is at sea level, he can rely on that voltage spec, sadly Honda doesn't give much more info about what the baro should read as it goes up or down. I only mentioned it, because there was a 2008 model on here that had the symptoms and it was the issue, but didn't throw a code. Since it's not throwing a code, it will not be out of the normal operating range and checking the voltage may or may not help, but won't hurt.
 
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