DT 300 - fail to start - TPS voltage value at 0 position ?

[Henry]

Hello,

My DT300 from 2011 has problems to start !
Cold start is ok after 3 sec cranking (minimum, when it should be half 1 !), hot start is a massive pain, it needs at least 10 tries, hopefully battery is ok !
After starting, everything is fine, but it's idling weirdly, sometimes the idle is at 2000rpm then it needs 10 secs to come down to 1700. It goes for a while after resetting TPS/ISC, but comes back after a few starts.
No error code on dash

Spark plug is OK, new + 0.6 gap
Coil is new, stator ok, pulser ok, 14.4V on charge, coil is OK.
Cylinder pressure is OK, 10 bars when the workshop manual says 12+/- 2
Leak pressure test is OK, no leak through valves, 5 psi (on 100) through rings (cols engine = normal)
Valve clearance OK
Fuel pump pressure OK
ISC resistance OK
Injector resistance OK, seems clean, sprays normaly (I think, I tested into a plastic jar, looks like a strong mist)

I took the throttle body for a clean, it was very dirty ! Cleaned everything
I messed up with the TPS, I didn't check its position before removing...

I have the diag Fi tool ordered, but I don't know the value the TPS has to reach when the throttle is closed.

I hope this will solve my problem !

Please don't hesitate if you think about something else

Thanks !

[Henry]

I have the Fi diag tool now
I moved the TPS according to the manual, it was at 0.77 at pos 0, it but it back to 0.6
But I still have the same problem, + the idle is higher now, a bit above 2000rpm, then after a long time (around 20 secs), goes back et 1800.

What a shame, I'm not desperate, but close to :-(

The data reading show .02 V for the O2 sensor at iddle on cold engine, could that be the problem ? It seems as he engine is cold the value should be higher no? .02 is lean, very lean when on a cold start it should be rich ! The O2 heater is on till around 70°celcius. Is that normal ?

[CROSSBOLT]

I have the Fi diag tool now
I moved the TPS according to the manual, it was at 0.77 at pos 0, it but it back to 0.6
But I still have the same problem, + the idle is higher now, a bit above 2000rpm, then after a long time (around 20 secs), goes back et 1800.

What a shame, I'm not desperate, but close to :-(

The data reading show .02 V for the O2 sensor at iddle on cold engine, could that be the problem ? It seems as he engine is cold the value should be higher no? .02 is lean, very lean when on a cold start it should be rich ! The O2 heater is on till around 70°celcius. Is that normal ?

I would recommend setting your TPS based on percentage. As I recall (take with grain of salt- I'm old and recall questionable!) set to achieve nearly 100% at wide open throttle (WOT) and see what you get with throttle closed. And how it affects idle. Take a look at that first page when running to see what the target rpm is for idle. Should be 1700 +/- 100.

You are right, a cold start should be richer that operating temp. Yes, the heater will cycle off and on to some preset schedule.

Idle is set in the computer and cannot be changed by grungies like you and me. The ISC, idle speed control is a motor driven valve that opens when you close the throttle. First look to see if someone previously tried to adjust the throttle stops. Adjusting is set and should NEVER be altered. The  ISC may not be running properly. It is a motor. 5 volts, I think. You may have to rig (cut open) a USB cable to get the black and red wires for 5 volts to run the motor on the bench.

These systems are super reliable, very durable and RARELY malfunction. The throttle body sensors are really well made and the ECU is very effective. The weak areas are the spring in the TPS that removes any slack so it follows the throttle precisely. Lack of lube or dirt will screw this up. MAP (manifold air pressure) sensor is sensitive to dirt and position since it can be mounted in one of eight positions. This may have been changed by the previous fingers.

Go one thing at a time and report back. I have a DT300i and an analyzer tool so I (and others) can back you up. We can even get on the phone (if you are in the US) and fiddle.

[Henry]

Thanks Karl for your answer !

I'll try to set the TPS based on %, for now, at .6V at 0%, it shows 90% at WOT. At that position the iddle speed targeted shows 1700 on the diag tool.

I'll check O2 value on a real cold start, yesterday the scooter was off for about 2 hours when I checked.

Simple check for the ISC is take it out of the throttle body, plug it and turn the key (witout starting  ), you will see it moving, you can even perform a TPS/ISC reset, you'll see the ISC going to 100% and come back. The ISC works in my case.

Concerning the TPS, I didn't know there is a spring inside, that sounds logic but I never thought about it ! Is there a way to access and clean that ?

The MAP sensor looks clean, no dirt under it. Are you sure the position could affect it ? As it is made of 6 holes in circle + a central one. The previous fingers must be mine 

The TPS setting I changed yesterday did nothing concerning my starting problem, still hard to start and almost impossible when the engine is hot, I still have to try and try several times, and sometimes I get a massive explosion through the exhaust ! That could bend the valves !!

The weird thing is that I almost have the same issue on my Downtown 350, 4 years old and 15k miles. I changed my 300 for the 350 4 years ago because all this starting problems were an issue for my job, I work in medical and I have to go to different locations into the city (Brussels) for emergencies, I needed something reliable and the 300 was a problem.
I kept it because the 350 is the same base and a lot of parts are exchangeable. Since the 350 is acting the same way, I took the decision to investigate on the 300 and try to solve the problem and maybe use it daily and the fix the 350 and keep one stored in good shape incase of problem.

I need to find the issue !

[CROSSBOLT]

Thanks Karl for your answer !

I'll try to set the TPS based on %, for now, at .6V at 0%, it shows 90% at WOT. At that position the iddle speed targeted shows 1700 on the diag tool.

I'll check O2 value on a real cold start, yesterday the scooter was off for about 2 hours when I checked.

Simple check for the ISC is take it out of the throttle body, plug it and turn the key (witout starting  ), you will see it moving, you can even perform a TPS/ISC reset, you'll see the ISC going to 100% and come back. The ISC works in my case.

Concerning the TPS, I didn't know there is a spring inside, that sounds logic but I never thought about it ! Is there a way to access and clean that ?

The MAP sensor looks clean, no dirt under it. Are you sure the position could affect it ? As it is made of 6 holes in circle + a central one. The previous fingers must be mine 

The TPS setting I changed yesterday did nothing concerning my starting problem, still hard to start and almost impossible when the engine is hot, I still have to try and try several times, and sometimes I get a massive explosion through the exhaust ! That could bend the valves !!

The weird thing is that I almost have the same issue on my Downtown 350, 4 years old and 15k miles. I changed my 300 for the 350 4 years ago because all this starting problems were an issue for my job, I work in medical and I have to go to different locations into the city (Brussels) for emergencies, I needed something reliable and the 300 was a problem.
I kept it because the 350 is the same base and a lot of parts are exchangeable. Since the 350 is acting the same way, I took the decision to investigate on the 300 and try to solve the problem and maybe use it daily and the fix the 350 and keep one stored in good shape incase of problem.

I need to find the issue !

Yeah, you need to fix that!
Explosion in exhaust is fuel build-up, I would think. Also two similar machines, same problem? What is common to both? Air and fuel.

Your EFI settings may not be the cause.....

This thing about MAP position is hearsay on this forum. There are past discussions that claim the position seems to improve the idle.

[mousejunks]

No engine or fault lights should mean that the sensors are ok and within range. Even then the engine can still start and run with some faulty sensor readings. When starting the bike try opening the throttle whilst pressing the start button.

If it is occurring on both the DT300 and DT350, it could be bad fuel. 

[Henry]

I don't think the fuel quality is involved, we have very good fuel quality here in Belgium, I only give 98 oct to both scooters and from different gas pumps.

I just thought about something... Could it be the battery ?! I didn't check for battery voltage as the charging voltage is ok (around 14.4V) on both scooters. I quite often check the charging voltage (I have a reading on the 350 dashboard) but I have no clue about the voltage of the battery itself. The battery on the 350 is the factory one, nearly 6 yrs old, the scooter stays outside at night, temp goes quite frequently under 32F in winter in Brussels.

After checking, battery is at 11.9 on the 350 ! Can't check on the 300 cause my garage is not at home, but I remember I replaced it about 7 years ago.

Could be the issue, so simple ! How didn't I think about that before
I ordered a new battery.

[CROSSBOLT]

I don't think the fuel quality is involved, we have very good fuel quality here in Belgium, I only give 98 oct to both scooters and from different gas pumps.

I just thought about something... Could it be the battery ?! I didn't check for battery voltage as the charging voltage is ok (around 14.4V) on both scooters. I quite often check the charging voltage (I have a reading on the 350 dashboard) but I have no clue about the voltage of the battery itself. The battery on the 350 is the factory one, nearly 6 yrs old, the scooter stays outside at night, temp goes quite frequently under 32F in winter in Brussels.

After checking, battery is at 11.9 on the 350 ! Can't check on the 300 cause my garage is not at home, but I remember I replaced it about 7 years ago.

Could be the issue, so simple ! How didn't I think about that before
I ordered a new battery.

Battery voltage under what conditions?
1. Absolutely no load (maybe the clock but key off) 12.6 is the fully charged max.
2. Key on (but not starting) 11.5 is what is normal with lights on in USA
3. STARTING (but not running) 9.5 absolute minimum. This is the voltage where "no spark" happens.
4. RUNNING (at idle) 13 and up to 14.5 is normal range.

[Henry]

Battery voltage under what conditions?
1. Absolutely no load (maybe the clock but key off) 12.6 is the fully charged max.
2. Key on (but not starting) 11.5 is what is normal with lights on in USA
3. STARTING (but not running) 9.5 absolute minimum. This is the voltage where "no spark" happens.
4. RUNNING (at idle) 13 and up to 14.5 is normal range.

No load, key off, 11.9V
Running at iddle, between 14 ans 14.5V

So charging is not an issue, but the battery seems tired !
I'll monitor while crancking, disconnecting the sparkplug cap incase it starts

Edit : I checked battery voltage on the 300, 13.5V !!! No load, scooter switched off for 2 days. I didn't have the key with me so no check while crancking, but that's weird.
I've had a lot of motorbikes in my life, nerver seen that...

[Henry]

Unfortunately the battery was not the problem...

My next investigation will be the fuel pump, I'll pop it off and see... Maybe the filter is clogged, could be, maybe...
I'm fed up with that thing, I already spent way too much time troubleshooting 

[mousejunks]

Back to the original issue - it was difficulty when starting hot but ok when cold? Could be the oxygen sensor or ECU.

Also remove you seat and look for any vacuum leaks, e.g. breather hoses from the crankcase and air intake. Look for any wires rubbing on anything.

[dr.jazz]

Hello,

You mentioned that you have a Fi diagnostic tool, check all the value as shown in the picture (diagnostic report).
Pay attention to the ignition timing and water temperature sensor when engine warm, and also reference voltage for O2 when engine is off (ignition on). You ask about O2 sensor behavior, when you turn on the engine, ECU works in open loop mode until the sensor heats up, that is why you have low voltage readings at start. When engine get warm up you should have O2 voltage cycling. Another very important thing, during the engine starting (cranking) ECU always work in open loop until starts so there is no way O2 sensor creates your warm start problems.

After you check everyting on list, we can move on 

[Henry]

Hello,

You mentioned that you have a Fi diagnostic tool, check all the value as shown in the picture (diagnostic report).
Pay attention to the ignition timing and water temperature sensor when engine warm, and also reference voltage for O2 when engine is off (ignition on). You ask about O2 sensor behavior, when you turn on the engine, ECU works in open loop mode until the sensor heats up, that is why you have low voltage readings at start. When engine get warm up you should have O2 voltage cycling. Another very important thing, during the engine starting (cranking) ECU always work in open loop until starts so there is no way O2 sensor creates your warm start problems.

After you check everyting on list, we can move on 

[/quote]

Thanks for the checklist ! I will check tomorrow and report.

[Henry]

Hello,

You mentioned that you have a Fi diagnostic tool, check all the value as shown in the picture (diagnostic report).
Pay attention to the ignition timing and water temperature sensor when engine warm, and also reference voltage for O2 when engine is off (ignition on). You ask about O2 sensor behavior, when you turn on the engine, ECU works in open loop mode until the sensor heats up, that is why you have low voltage readings at start. When engine get warm up you should have O2 voltage cycling. Another very important thing, during the engine starting (cranking) ECU always work in open loop until starts so there is no way O2 sensor creates your warm start problems.

After you check everyting on list, we can move on 

I checked with the Fi tool, everything looks within specs. I did that on the Downtown 350, I have no access to my 300 for now, but they both suffer the same problem and the specs from the 300 are identical to the 350 (Sensors are the same)

Warm engine : I don't know if it is normal but on page 4 the heater activation goes on & off quite quickly and the engine is hot ! (89°C), I did 2 pics of page 4, one on one off.










Cold engine :


At WOT







What do you think ?

[CROSSBOLT]

I checked with the Fi tool, everything looks within specs. I did that on the Downtown 350, I have no access to my 300 for now, but they both suffer the same problem and the specs from the 300 are identical to the 350 (Sensors are the same)

Warm engine : I don't know if it is normal but on page 4 the heater activation goes on & off quite quickly and the engine is hot ! (89°C), I did 2 pics of page 4, one on one off.










Cold engine :


At WOT







What do you think ?

Looks pretty normal to me. I think there is a common power interruption possibility that would be sensed as turning the systems off and on. Something that would not be sensed as a fault, hence no code. Could also be a bad plug cap and/or plug wire. Also could go back to low voltage to the ECU while cranking. I know you measured really good voltage while trying to start measured at the battery. But what is the voltage AT the ECU?

You have been handed a toughie on this one! Two machines with the same symptoms but otherwise perfectly envious performance otherwise. Write down everything that has been ruled out. No dealer tech ANYWHERE would even be allowed to sort this out. Right now, YOU are the world's ranking true authority. Why? You are there, you have the analyzer tool (that most US dealers do not have), you have the motivation to solve because you actually use this mode of transport daily, you have the ability (demonstrated) potential and I will think up a couple more reasons soon!

We all will benefit from your discovery.