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Discussion Starter #1
Hello everyone, I have a 2000 gsxr 750 that I believe is running too rich.
Symptoms: blipping the throttle chokes the bike. Spark plugs black.
I have NO, I repeat NO, fault codes. TPS is centered. -C00
I have checked ALL the sensors & ALL are within specs.
Fuel filter was back flushed, fuel pump is within specs of output. Fuel pressure is within specs.
Air filter is clean. Yoshi bolt on exhaust. Other than that it's stock.
No black smoke during or after start up.
After installing new spark plugs the bike ran great, bike did NOT choke on blip of the throttle, BUT after it ran for a few mins the choking can back.
IDK what else to check or do now. I NEED HELP!!! :crying
 

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Hello everyone, I have a 2000 gsxr 750 that I believe is running too rich.
Symptoms: blipping the throttle chokes the bike. Spark plugs black.
I have NO, I repeat NO, fault codes. TPS is centered. -C00
I have checked ALL the sensors & ALL are within specs.
Fuel filter was back flushed, fuel pump is within specs of output. Fuel pressure is within specs.
Air filter is clean. Yoshi bolt on exhaust. Other than that it's stock.
No black smoke during or after start up.
After installing new spark plugs the bike ran great, bike did NOT choke on blip of the throttle, BUT after it ran for a few mins the choking can back.
IDK what else to check or do now. I NEED HELP!!! :crying
I think I remember Chuckster mentioning somewhere that a loose or broken hose to the IAP sensor will cause a rich condition.

Easy to check anyway.

I'm assuming you don't have a PC or other aftermarket fuel controller on it.

I don't think these ECMs are that smart to catch the implausibility of high manifold pressure yet a near closed throttle position.
 

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Discussion Starter #3
I have checked the vacuum lines to the IAP sensor all are clear.
No power commander installed.
I thought I had a bad intake air temp sensor, so bought another one and they are both reading 2.25+- at 70 degrees. Which is within specs.
If the crankshaft sensor is bad or going bad will the bike still run? Read it could/can throw the injector volume off.
 

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I have checked the vacuum lines to the IAP sensor all are clear.
No power commander installed.
I thought I had a bad intake air temp sensor, so bought another one and they are both reading 2.25+- at 70 degrees. Which is within specs.
If the crankshaft sensor is bad or going bad will the bike still run? Read it could/can throw the injector volume off.
I really don't know a lot about your year bike, on the later bikes, about K4 and up. The CKP sends pulses to the ECM that sends them to the tachometer. I would suspect you would be getting some erratic tach readings.

You could confirm this with the wiring diagram in the back of the service manual.

A defective CKP would not allow a bike to start or run but would also throw a code.

There were some posts over the years of bikes that would not start when hot that were finally fixed with a new CKP sensor. No codes there either.
 

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Discussion Starter #5
Your loosing me here rv6john.
my bike runs !! It just runs RICH.
""I would suspect you would be getting some erratic tach readings."" Tech is pretty steady with the rpms.

I would think if the CKP sensor or cam sensor was bad it would not run. Maybe that's what you was thinking, but again my bike runs. Idles just fine at a steady 1250 rpms.
I just can not figure out why its running rich.
Is it possible for a exhaust leak to cause the bike to run rich?? If so what causes it, by that I mean what is telling the ECU to run rich? Bike has no O2 sensor
Bike has NO fault codes.

What type of program can I get to adjust the air/fuel ratio ??
PLEASE PASS THIS ON TO THE OTHER LONG TERM EXPERIENCED MEMBERS HERE FOR ME.
 

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If the crankshaft sensor is bad or going bad will the bike still run? Read it could/can throw the injector volume off.
Sorry, just replying to what you asked in your post.
 

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Discussion Starter #7
My bad rv6john.. I got ya now.
So this video is after cleaning the fuel injectors, fuel filters, changed spark plugs..etc.
Runs a little different, sounds BETTER but still bogging down. NOTICED the smoke now more.
 

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Hello,

Since you have tested all the sensors, & believe them to be in good working order, I'd do a thorough scan of all the vacuum hose fitted. They're 15-years old now, & should have signs of cracking, & lost their rubberyness. This means that they can leak once fitted, & splits can be hard to find.

I'd then be inclined to check throttle cable play, & especially choke cable adjustment & its release position. If OK, then set idle speed again if needed.

Next is synchronizing the throttle valves...you will need a "Motion Pro" carburetor synchronizing gauge. It's much cheaper & better than the OEM gauge. Follow the instructions to synchronize. The Suzuki manual has different test-rpm than the Motion Pro gauge set. Choose your own method. Either way will provide the nearest optimum settings.

It's also possible that you have bad fuel &/or collected some water along the way.

Hope this helps,

Rastus
 

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Discussion Starter #10
Rastus: Thanks for your reply.
I did check ALL the vacuum hoes while I had the tank off. All the hoes were clear, I bent them to try to find a crack/damage. Nothing, all was good, I applied WD-40 on the outside to help protect the hoes.
Throttle cable checked, it's not tight, it has small amount of play like the manual states. Plus it idles at 1250.
Choke is totally "relaxed". It still works. But again choke is totally off, idles at 1250.
As for syncing the throttle bodies, I made a home made unit for my 2004 ZZR-600. Worked pretty good. I might make another one just to "see" where they are, and if they or one is out i'll buy one.
When I had my tank off cleaning the filters, I looked inside the tank. Looked pretty good. I did drain 99% of the fuel out & partially filled it up with different gas just to see if I did get some bad gas, but it still ran the same.
 

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Discussion Starter #12
UPDATE: 6/9/2016
Bike still running rich,....I guess.
So I rechecked my IAP sensor, here's what I found: getting correct voltage to sensor. 4.5-5.5
Pulled sensor & hooked up a syringe to a short hoes connected that to IAP sensor, hooked up voltmeter to sensor. At ambient pressure voltmeter showed 2.66 V. I pushed 5ml of air into sensor voltage changed (went up). I pulled back on the syringe producing a vacuum & the voltmeter again changed (went down) to 1.55. So according to manual is good.
Put IAP sensor back on bike, connected everything, stuck 1/2 paper clip in the connector (Green) or half in the Black wire so I could get live readings of the IAP signal to ECU.
READINGS: Cold start @ 1250 idle 2.66 volts.
Warmed up @ 1250 idle 2.45 volts.
Warmed up @ various rmps the volts when UP to 3. something then down to low 2. something.
Someone correct me if I'm wrong but shouldn't the volts decrease with an increase of rpms ?? Mine went up then down. STRANGE.

So, I removed the IAP sensor, started the bike. It ran about the same as before. Crappy.
I hooked up a battery, creating my own "false" signal, to the connector to the ECU.
READINGS: 1.5v battery bike would NOT run. Kept dying, figured it was "flooding out".
3.7v battery bike ran AWESOME, throttle was responsive like it's suppose to be BUT BUT BUT it was throwing flames out the exhaust pipe. SO WTF DOES THAT MEAN !!??

Does that mean my IAP sensor is really BAD ??
What is causing the flames out the exhaust ?? I mean it's kinda cool looking but I don't want to mess something else up if I run it with the "false" signal.
 

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Discussion Starter #13
"I'm curious as to how you make out with this. "

Don't know what that means..... your wondering how I'm going to fix this issue ??
Sh*t ....me too. I'm stumped.
 

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"I'm curious as to how you make out with this. "

Don't know what that means..... your wondering how I'm going to fix this issue ??
Sh*t ....me too. I'm stumped.
I've got the same bike essentially and if you're having a problem like this it stands to reason that I might someday too. That's all. Seems like you're going through all the right problem solving steps. Good luck.
 

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Hello,

Time for some fresh high octane gasoline, & some STP injector cleaner. Then go for a long, enjoyable ride.

Your black pugs may be the result of poor injector spray.

Everything that you've done to trick the computer, has done exactly that, & it's responding to the ROM-map in place for the voltages being fed into it.

At idle, there's a less than 1-Bar pressure being sensed. Crack the throttle, & there's a momentary rise of pressure that nears 1-Bar pressure. You computer feeds extra fuel at this point into the motor, to avoid a hesitation or flat-spot, & that then allows the engine to rev-up accordingly, by allowing the injectors to stay open longer. (This is what an accelerator pump does on a carburetored car). Once the RPM's have reached the max allowed by the throttle-position, the air pressure will lower again to near 1-Bar. This is based on no-load on the engine, revving & holding the throttle constant in your garage. Under load, throttle position alters to cater for load & road-speed. ( This is to be understood based on gauge pressure, not absolute pressure ).

Since you've "fixed" the voltage feed of the IAP sensor, you will get many & varied responses from your motor at different rev-ranges, as it's supposed to "change" with the RPM's, according to the maps in the ECU.

Once again, try fresh high-octane gasoline, some quality injector cleaner, go for a ride & enjoy yourself !!!

Cheers,

Rastus
 

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Discussion Starter #16
Rastus:
The other day I pulled the injectors attached a fuel hose to the injector(s) at one end, attached a 10ml syringe to the other end of the fuel hose, filled the syringe with B-12 Chemtool fuel injector cleaner the attached 12v to the injector & flushed each injector. Also reverse flushed the injectors too. So I'm pretty sure they are clean. The small screen filter at the inlet was clean.
The injectors "spray pattern" was a straight line. I was expecting a fan or cone type of spray pattern. Do you think this is a problem or do you think it's just because of how I had it all hooked up. I did apply pressure to the syringe before & during each flush.

"Crack the throttle, & there's a momentary rise of pressure that nears 1-Bar pressure. You computer feeds extra fuel at this point into the motor, to avoid a hesitation or flat-spot, & that then allows the engine to rev-up accordingly, by allowing the injectors to stay open longer." <-- This is where my bog down happens. (while IAP sensor is hooked up normally). To me it seems like it's running too rich & choking/smothering the bike.

"Since you've "fixed" the voltage feed of the IAP sensor, you will get many & varied responses from your motor at different rev-ranges, as it's supposed to "change" with the RPM's, according to the maps in the ECU." <-- I was only messing around trying to find out what's causing it to run rich. Since I have no fault codes, all my sensors checked out to manual specs, something SOMETHING has to be messed up somewhere. But setting the "fixed" voltage on the IAP did make the bogging throttle go away, with no load, but the exhaust made my nose burn. I had the bike in my garage, with a fan running to pull/push the exhaust fumes out the door. It's a industrial fan not a box fan. I'm thinking about ordering a IAP sensor $8 just to see if it helps, if not i'll be looking for a PC III. I actually have a PC III but it's for a 2002-2003 gsxr 750. So if you know anyone looking for one....
 

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Discussion Starter #17
LimitedRR: I have a 2002-2003 Power commander III USB for sale if you know anyone who wants to buy it. Bought it for my bike but it's the wrong model. The one I have is the 307-410. I need the 305-410. If you know anyone who has the 305-410 let me know, all the ones I've found are $265+.
If I EVER figure out what's causing the running rich/throttle problem I will defiantly post it on here.
 

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Discussion Starter #18
Catch122:
Line 6 at the top on original post states I have a CLEAN air filter.
Injector O-rings are good, post cleaning the injectors I had to replace one 0-ring. NONE are leaking now. Cleaning the injectors didn't fix the problem.

"Your input was digital throughout the rpm band. Rich is vac or load is the demand signal. So if you think about it, you mechanically set the load-(throttle open)." <-- I was just trying to fix the bogging throttle, which setting the "fixed" signal DID fix the bogging throttle but that was with NO load, & the exhaust fumes made my nose burn.

I have ordered another IAP sensor $8 just to see if it helps, if not I'm in the market for a PC 305-410. No one around here has a dyno or a air to fuel ratio adjusted machine.
 

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Hello,

Yes, that spray pattern doesn't seem good ! If it's possible to remove the injectors & run the actual fuel-pump fitted to then check the spray pattern, that's what I'd be doing...The spray pattern should appear cone shaped & like a mist of fuel with no droplets. This is quite dangerous to test, so ensure there's no spark-source near by when you do this.

Also don't forget about the basics too, like your tappet clearances etc, as a non-seating intake valve(s) will alter the pressure that your sensor reads.

It's also possible that your intake manifold(s) may have leaks to. Once up & running, spray some CRC or WD-40 around the intake manifold surfaces, & if there's a momentary but noticeable difference to the way the engine runs, chances are you have a leak. I'm pretty sure that these engines have an "O"-ring mounted into the cylinder-head, that the manifold then lightly crushes to create a seal. Rubber is rubber, & who knows when it will fail ?.

Good luck,

Rastus
 

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Discussion Starter #20
Rastus:
Thought bout the fuel injectors not spraying right, like you said, so did a little research on fuel injector spray patterns. I thought all fuel injectors sprayed in a cone shape when working correctly. Turns out there are different injector spray patterns. Some cone shaped others more straight line, some off centered. There is no description of the correct pattern for my bike in the service manual, so I called the local so-called Suzuki dealer to see if they knew the spray pattern. They did not.
Found some pictures online showing mixed info on the correct spray pattern but again it goes back to the type of injector. So I'm confused on the correct spray pattern for my bike.
I will remove the injectors & fuel rail, try to hook it up to the fuel pump & record my spray pattern & post.
Here are some pics I found:
 
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