Need a good shop to diagnois fuel injection problem | GTAMotorcycle.com

Need a good shop to diagnois fuel injection problem

I

Ikan

Well-known member
Looking for a shop that is good at diagnoising and fixing a stock Suzuki GSXR750 2003.

The bike will not rev up past a specific point. When it picks a point it will always be that exact RPM point. Position of throttle or the pace at which I open the throttle has no effect. Gradually the rev limit is dropping over months. At a certain point it is like a SOFT rev limiter cuts in.

Just below that limit it will run all day long like nothing is wrong. Say 100 rpm below the cutting out spot. This has been an onging problem for a while, 20,000 kms!!!. The local dealer is useless for help. I can only check so many things due to equipment....

New:
- fuel pump/filter/regulator assembly
- TPS (Throttle position sensor)
- battery

Used:
- ECU


All sensors voltage in/out and to ground checks are ok.
MAP (IAP - Intake Air Presssure)) sensor vacuum checked ok.
Checked and cleaned the CKP, crank position sensor. Dealer checked Peak Voltage on CKP.
Dealer said fuel pressure may be 38 psi but they were not confident in their gauge. Spec is 42 psi. So I put a new one in.


The bike does not have a dust bunny or corroded spot on it. Clean as a whistle as they say, inside and out.
Does not burn a drop of oil, litrerally, between 5,000 km oil changes.
No fluid leaks.
Frame, grounds, connections, fuses and fuse boxes are like factory new. As are all electrical connections.
Inside the fuel tank, fuel rails are spotless clean.
Air filter and intakes clean.
New sparkplugs.
Ignition coils resistance check ok.
Fuel injectors pass electrical checks per Haynes manual.
Visually inspected each fuel injector's inlet screen filter which appear clean.
No unusual noises.
No codes on dash.

It does it in any gear (1st to 6th), on the sidestand in neutral or in neutral with the sidestand up.
Bumps have no affect. Rain has no affect.

Bike stored indoors always.
Seafoam fuel injector cleaner recently tried.

I put almost 7,000 kms on this bike in the past 3 weeks. The limit, cut out, rev no higher is now down to a new spot. No more trips until it is fixed.

When it cuts out say at 10,000 it will climb to 10,500 chugging, max. But no higher.
Its new limit is now 7,000 rpm. Chugs up to 7,500. Will run at 6,800 all day long just fine.
Always starts instantly and runs great until a point.


Help, please.
 
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You say no codes on dash,have you checked for codes in the ECU(history or current)using flash or the scan tool.Has the FI light ever come on that you may have seen or not seen?
 
rocket12r said:
You say no codes on dash,have you checked for codes in the ECU(history or current)using flash or the scan tool.Has the FI light ever come on that you may have seen or not seen?
Click to expand...


Thanx for the input.

No I have not as I do not have a scan tool. Don't know about flashing.
Being as it is an early generation fuel injectiion system I am told they cannot be diagnoised as easily with tools. The capability is not there. I do not know if this is 100% true.

I have owned the bike from new and no lights or code has ever appeared that I am a aware of.
I did make a jumper to use at the connection under the seat for code accessing. Saw nothing as far as as codes.....

I am using a Haynes shop manual. Do not have a Suzuki shop manual.
 
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Ikan said:
Thanx for the input.

No I have not as I do not have a scan tool. Don't know about flashing.
Being as it is an early generation fuel injectiion system I am told they cannot be diagnoised as easily with tools. The capability is not there. I do not know if this is 100% true.

I have owned the bike from new and no lights or code has ever appeared that I am a aware of.
I did make a jumper to use at the connection under the seat for code accessing. Saw nothing as far as as codes.....

I am using a Haynes shop manual. Do not have a Suzuki shop manual.
Click to expand...

Thats not true your bike has a its own diagnostics built into the ECU and gauge, simply jumping 2 wires in a clip under your seat will put the bike in "dealer mode" and it will display error codes for any malfunctioning components...When you pay a shop or dealer to diagnose your bike that is simply what they will do
 
I have little experience with fuel injected motorcycles, my FI experience is mostly with cars, so take this with a grain of salt, but it looks like an iffy cylinder position pickup sensor. At a certain RPM the sensor signal is deterioration too much to track.

I assume that's what the reluctor ring comment was above, as these sensors are commonly reluctance sensors.

The problem could be a specific problem with the sensor or pickup wheel or possibly a bad connection to the sensor. I had an issue a couple years ago, where a nick in the wire coating had allowed the wire to corrode, which eventually gave me errors.
 
JohnnyP636 said:
Thats not true your bike has a its own diagnostics built into the ECU and gauge, simply jumping 2 wires in a clip under your seat will put the bike in "dealer mode" and it will display error codes for any malfunctioning components...When you pay a shop or dealer to diagnose your bike that is simply what they will do
Click to expand...


Thanx I forgot the terminology. When I put the jumper in it put it into "dealer mode'. No codes or anything appeared. Never. I have done this a few times over the past year.

If it helps, it all started after sitting stored in an unheated garage over winter. I know it revved up ok when I put it away in late fall. For storage I put in fuel stabalizer, change oil and filter. Then take it for a 5 minute ride to ensure stabilzer gets through the fuel system. Then park it and take the battery out. I put a sock or rag in the muffler and intake ducts ti stop anything from crawling in there. I can see completely through the intakes and they are clean.

May have to take the covers off again and recheck wheel and ckp sensor with a magnifying glass to look for a crack.

The reluctor wheel looked ok on 1st casual look 7,000 kms ago. At least it is getting worse so eventually it might just stop running which should make it simple to trace the problem. Luckily I have another bike to ride. :). But this is my favorite. I rode it to the Tail of of the Dragon .... 3 weeks ago.

The secondary throttle valves move correctly at start up and when I rev it in neutral with the air filter housing lid off so I can watch.

Bike has 67,000 kms on it. It runs like a brand new bike up to a specific rpm. Starts instantly. No drop in fuel mileage which is something I always monitor at every fill up as I reset the trip odometer since new.

Me and dealer believe it is not a single cylinder type problem but rather something that is affecting the whole engine ( all 4 cylinders).
 
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theraymondguy said:
How badly stretched is the timing chain @ 67K? This could purely be a result of valve timing.
Click to expand...

Don't know about that.
It all started at about 45,000 kms.
One more thing to check.


The problem could be a specific problem with the sensor or pickup wheel or possibly a bad connection to the sensor. I had an issue a couple years ago, where a nick in the wire coating had allowed the wire to corrode, which eventually gave me errors.
Click to expand...


I also inspected the CKP (crank position sesnor) wires and it looked fine as in no chaffing or wear marks.

It always happens at say, (decreasing in rpm limit over months) approx.: 11,000, 10,000 9,000 and now 7,000 rpm. Never at say, 10,300, 8,200, 7,700....

I spoke to a shop manager at another long time around Suzuki, Yamaha, KTM... dealer who thought it was the TPS, Throttle Position Sensor. He said Yamahas go through them like donuts through a police officer as the joke goes. He said they test ok but are not ok, so always buy a new one never a used one. That is what lead me to get a new one.

Both dealers tell me because the 2000 - 2003 600/750 are 1st generation fuel injection it is not unusual to not have a fault code and that it basically comes down to trial and error with parts. Which can get expensive as can be imagined.

My local shop does not work on a lot of sportbikes and laughing said most SS bikes are written off by 15,000 -20,000 kms in their experience. So they do not have a lot of experience with this bike even though I bought it from them. Hence why I asked if there is a shop/person with experience with this bike.
 
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Early FI systems did not have as much I.O. or strict tolerances as later model units. Items like valve adjustment, valve timing (camshaft angle sensor), fuel starvation etc. are beyond the monitoring of early FI (and still some later model systems).

Find a competent mechanic, get the engine to TDC and a leak down test (listen for blow by in the intake and exhaust) on each cylinder. If you've got leakage through all cylinders, check cam chain and adjuster for wear (common) and valve adjustment (also common).
 
Ikan said:
Thanx I forgot the terminology. When I put the jumper in it put it into "dealer mode'. No codes or anything appeared. Never. I have done this a few times over the past year.

If it helps, it all started after sitting stored in an unheated garage over winter. I know it revved up ok when I put it away in late fall. For storage I put in fuel stabalizer, change oil and filter. Then take it for a 5 minute ride to ensure stabilzer gets through the fuel system. Then park it and take the battery out. I put a sock or rag in the muffler and intake ducts ti stop anything from crawling in there. I can see completely through the intakes and they are clean.

May have to take the covers off again and recheck wheel and ckp sensor with a magnifying glass to look for a crack.

The reluctor wheel looked ok on 1st casual look 7,000 kms ago. At least it is getting worse so eventually it might just stop running which should make it simple to trace the problem. Luckily I have another bike to ride. :). But this is my favorite. I rode it to the Tail of of the Dragon .... 3 weeks ago.

The secondary throttle valves move correctly at start up and when I rev it in neutral with the air filter housing lid off so I can watch.

Bike has 67,000 kms on it. It runs like a brand new bike up to a specific rpm. Starts instantly. No drop in fuel mileage which is something I always monitor at every fill up as I reset the trip odometer since new.

Me and dealer believe it is not a single cylinder type problem but rather something that is affecting the whole engine ( all 4 cylinders).
Click to expand...

If there are any codes being pushed out by the ECU, the FI light will be on when not in dealer mode. Then once in dealer mode it will display C codes instead of just flashing a FI light...In the Suzuki manual there is a chart where the C codes are explained...If there are no codes the gauge will display C00
You can see a list of Suzuki fault codes here
http://wotid.com/gsxr/content/view/15/35/

Question.....when was the last time you changed the spark plugs? Air filter?

Generally the most common problem Ive had with Suzuki GSXR's of that generation is with the secondary throttle servo motor...Its a very common problem on that generation of GSXR, and it will show a C28 fault code

Also there could be a chance that even thou you used stabilizer the gas is still bad....
 
JohnnyP636 said:
If there are any codes being pushed out by the ECU, the FI light will be on when not in dealer mode. Then once in dealer mode it will display C codes instead of just flashing a FI light...In the Suzuki manual there is a chart where the C codes are explained...If there are no codes the gauge will display C00
You can see a list of Suzuki fault codes here
http://wotid.com/gsxr/content/view/15/35/

Question.....when was the last time you changed the spark plugs? Air filter?

Generally the most common problem Ive had with Suzuki GSXR's of that generation is with the secondary throttle servo motor...Its a very common problem on that generation of GSXR, and it will show a C28 fault code

Also there could be a chance that even thou you used stabilizer the gas is still bad....
Click to expand...



There has never been a FI light or code on the dash. Never. The dash displays C00 in dealer mode. There has never, never, never been any C.. code.

This all started in the spring of 2011. I put new sparkplugs in it then and a new air filter. New air filter this spring also. All passages, intakes....are clean. Not a dust bunny. Literally. The bike is in near showroom condition. It has never been raced or dropped. In fact it only would be revved over say 8,000 a few times in a summer. But more often recently just to see if it would rev up.

Last summer it would stop revving at 11,000 or 10,000. On any day it would pick one of those 2 limits and stick with it for the day. Weird. Did not matter how many times I started and stopped the engine on that day.
But this summer it picked 10,000 (like it has its own mind). But recently the limit dropped to 9,000 and in the past weeks has now limited itself to 7,000 rpm.

The fuel tank has been emptied a few times. Recently when the new fuel pump/filter/regulator assembly was installed. I have never found a spec of dirt in the fuel tank or on the fuel pickup sock. No discolouration inside the tank. No water. No hissing sounds to suggest a plugged fuel tank vent.

This has been happening going on 2 summers. I am wondering now about the camchain stretching as suggested. I don't know. Lol.

It does not backfire, cough or sputter but only has like this soft rev limit it hits. I know what a hard rev limit feels and sounds like from when it used to do it correctly at 13,500 rpm.

Thanx for all the input and ideas so far.
 
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What do the plugs look like? Who's looked at them?
Looking at the spark plugs is the easiest way to have a look inside the engine and determine if certain basic issues are present or not (misfire, rich, lean, oil burning, etc).

To be honest, the first thing I thought when you described your problem is an ignition breakdown. Has anyone pulled the coils (one at a time) while the engine is chugging? This would quickly tell you if the problem is isolated to a single cylinder or two, or if it's a engine wide issue.

I would suggest starting at square one with the troubleshooting, I think something basic is being overlooked.
 
Spent only a few minutes today.
I agree it appears to be something basic I am overlooking/forgetting.
I have not had to think about this kind of stuff for years.

Put it into dealer mode = no fault codes. TPS adjusted ok.
Air filter, box, intake inlets all clean.
Sparkplugs a bit browner than would like but all 4 are burning the same (colour, light carbon deposit on outer ring). Tip is square like new. Gaps ok. Will install new plugs tomorrow.
 
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