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Tartan Dave
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Discussion Starter • #1 10 h ago
My brothers Sprint will not start unless you spray ether into the filter. Once started it will run perfectly until you stop. It will not start again unless you use more ether.? Had 2 local bike mechanics check it out, neither could solve the issue, that's why I have joined this pool of knowledge hoping someone can shed some light .
Its as if the ECU is not firing the injectors resulting in no fuel supply. The starting fluid gets it started and the ECU must be working as it should. Maybe some sensor is telling the ECU not to pulse the injectors but once started all is well. As i said the bike runs fantastic when started, but its a **** if you stall at the lights. I have checked all switches which can cause non starting like stand, clutch, fall but they would stop it cranking over and it always cranks. It has a new quality battery, injectors have been cleaned, tank removed and washed out, oil level checked, crank sensor checked,speed sensor checked, pump is pumping to required pressure and new plugs. Tune ECU ( and a more sophisticated analyser used by one of the mechanics ) both show no error codes. We also changed the ECU and downloaded a suitable map. Both ECU's work fine when the bike is started. Have scoured the forums looking for a solution to no avail.
The above issue began when the bike would not crank over as it should, so we charged the battery. Next day it started, so we thought ok flat battery, problem solved. Next day it cranked over sluggishly, so decided to replace the battery which we did with a new $170-00 unit. Turned over well, but no start, which is where we are some 2 months later.
Help Please
Thanks Dave
 

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Is the fuel pump priming the system when the key is turned? You should hear it run for a couple of seconds Maybe there's not enough pressure in the fuel rail to get the engine started but once started with ether, the pump kicks in to provide enough fuel?
 

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Good point, but yes you can hear it priming as you say but I will check it again to confirm. Obviously no problem with pump when it has started, it goes well, no lack of fuel.
The last mechanic who attempted to fix it reckons he replaced a faulty injector and cleaned the other 2 and checked the pump pressure.
Thanks
 

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Could this possibly be a dirty CPS? My thinking is that if the CPS is not sending the correct signal at the correct time to the ECU to fire the injectors -if indeed that is how it all works- then it may make sense that the starting fluid will get things going and the bike will run until the next shut down. This may be all rubbish but simple to check.
 

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Thanks Ulster Spud. I checked the Crank Sensor early on in the mystery as I thought the problem was caused by no spark.! I tested the spark with the tank removed and of course No Spark which I now know must have been due to the fuel pump and sensor being disconnected ( I think ). Obviously it sparks as it runs great when encouraged with some liquid dynamite, so fuel supply is the road I'm travelling. I think for whatever reason the injectors are not injecting OR the fuel mix is so lean and not being adjusted for starting mix ( richer ) caused by ???.
Also note that neither TuneEcu which I used or a more professional analyzer used by the last mechanic did not show up any faults.?
 

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Well aside from recommending a Haynes manual (sorry but it is good), in the troubleshooting section, it suggests that there may be an air leak between the throttle body and air intake manifold (check it's fitted correctly) or a leaking gasket. It also suggests the idle air control unit, but if you have already attacked the bike with a diagnostic tool, that seems unlikely.
 

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Starting with a fully charged battery, what is the voltage at the battery while cranking? It's been written many times here that these models are very voltage sensitive and even though it appears to crank sufficiently strong, the coils still need good voltage to provide a strong spark. Just wondering if the starting fluid works with a weak spark to fire the motor and then the voltage rises to keep everything running. Did you pull the plugs after a no start to see if they were wet?
 

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Hi I have a 2006 ST and a few years ago it started being hard to restart hot ,had to spray starting fluid in it to restart it ,cold it crank a long time ,I have the factory book and reading through the baro sensor give the ecm the reading used to start the bike ,baro and map are the same part number ,I replaced mine with a used one for under 20 bucks and it has been fine ,i hope this helps
Charlie
 

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I think it's the other way around. The map that is mounted on the top of the air box give the ECM a reading of the intake pulses so that it knows which is the intake stroke vs the combustion stroke.
719048

The barometric sensor gives the atmospheric pressure.
719049

If I remember well you can even invert them in order to check the value w/ tuneECU. As far as I remember the baro pressure is displayed in the TuneECU. So you can check both baro and map w/ the same reading in TuneECU.
719050
 

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Hi I have a 2006 ST and a few years ago it started being hard to restart hot ,had to spray starting fluid in it to restart it ,cold it crank a long time ,I have the factory book and reading through the baro sensor give the ecm the reading used to start the bike ,baro and map are the same part number ,I replaced mine with a used one for under 20 bucks and it has been fine ,i hope this helps
Charlie
Thanks Charlie. Did you by chance spray any starting fluid to see whether it would start with some encouragement.? Mine will start no problems with the magic gas. I think if it were an issue with the ECU not knowing when to spark due to a failing Pressure switch it would not make any difference spraying gas into the air intake. But thank you for the suggestion.
Rgds dave
 

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Discussion Starter #13
I think it's the other way around. The map that is mounted on the top of the air box give the ECM a reading of the intake pulses so that it knows which is the intake stroke vs the combustion stroke.
View attachment 719048
The barometric sensor gives the atmospheric pressure.
View attachment 719049
If I remember well you can even invert them in order to check the value w/ tuneECU. As far as I remember the baro pressure is displayed in the TuneECU. So you can check both baro and map w/ the same reading in TuneECU.
View attachment 719050
Thanks Fredsprint, but do you think it would start with gas and run perfectly when started if this was a problem?
 

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Starting with a fully charged battery, what is the voltage at the battery while cranking? It's been written many times here that these models are very voltage sensitive and even though it appears to crank sufficiently strong, the coils still need good voltage to provide a strong spark. Just wondering if the starting fluid works with a weak spark to fire the motor and then the voltage rises to keep everything running. Did you pull the plugs after a no start to see if they were wet?
Hi UlsterSpud
I did a check on the battery voltage and it was 12.3v dropping to 11.1v when cranking. I would have thought this to be good. It is a new quality fully charged battery.
And No, I did not check the plugs to see if they were wet after cranking ( which is something I should do) but you can smell petrol coming out the exhaust so I am assuming they would be wet.
I dont know that I should be assuming anything at this stage!! .
I have checked the voltages on the pump and injectors when cranking. I also put the multimeter on AC voltage on an injector plug as we are looking for a pulse milliseconds long , I got .5v reading on cranking, the fact that I got anything means that there is activity, presumably a pulse from the ECU ( bit primitive but my oscilloscope packed up years ago )
I am wondering whether the fuel pump is actually pumping reliably. Maybe once its started ( with the magic gas ) and getting more power from the alternator this compensates for any weakness in the pump. Tomorrow I will jumper a car battery and see if this makes any difference. If so, I would suspect the pump is the problem. Thanks again for input.
Rgds Dave
 

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Thanks Fredsprint, but do you think it would start with gas and run perfectly when started if this was a problem?
I already heard about some sprint not starting because of that sensor. I don't think the guy tried w/ starting fluid though. Worth trying though.
A good indication would also be the values when trying to balance the throttle body. They shouldn't be realistic. That's the same sensor.
A bad sensing of the strokes when starting would result in injecting on the wrong one while cranking.

As already mentioned the crank position sensor could also be the culprit as it provides a lower voltage signal when cranking just because it's a magnetic sensor (like a guitar microphone). So once started over (w/ starting fluid) thus reaching a higher rotation speed it provides a sufficient voltage peak to peak. But you said you double checked it so... In addition there wouldn't be any spark as well.
But my experience tends to show (mainly on cars) that CPS while not preventing the engine to run OK rends the starting erratic and difficult until it's completely shot.

Any sensor values should be checked on TuneECU just to see whether the values are consistent (temp, pressure...)
 

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Hi UlsterSpud
I did a check on the battery voltage and it was 12.3v dropping to 11.1v when cranking. I would have thought this to be good. It is a new quality fully charged battery.
And No, I did not check the plugs to see if they were wet after cranking ( which is something I should do) but you can smell petrol coming out the exhaust so I am assuming they would be wet.
I dont know that I should be assuming anything at this stage!! .
I have checked the voltages on the pump and injectors when cranking. I also put the multimeter on AC voltage on an injector plug as we are looking for a pulse milliseconds long , I got .5v reading on cranking, the fact that I got anything means that there is activity, presumably a pulse from the ECU ( bit primitive but my oscilloscope packed up years ago )
I am wondering whether the fuel pump is actually pumping reliably. Maybe once its started ( with the magic gas ) and getting more power from the alternator this compensates for any weakness in the pump. Tomorrow I will jumper a car battery and see if this makes any difference. If so, I would suspect the pump is the problem. Thanks again for input.
Rgds Dave


Hi Dave,
If you are smelling petrol at the exhaust after a fail to start then one would surmise that the pump is priming sufficiently and that the injectors are spraying fuel, though perhaps not necessarily at the correct time. I still go back to the CPS and wonder how you checked it? Did you remove and clean it or simply meter it? It's just a Hall effect switch but may switch intermittently if the sensor is fouled. I'm running out of ideas here.
 

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I'm not sure how I messed up my last post replying to Tartan Dave but one needs to click on "click to expand" to read it! I'll add it to this post.

Hi Dave,
If you are smelling petrol at the exhaust after a fail to start then one would surmise that the pump is priming sufficiently and that the injectors are spraying fuel, though perhaps not necessarily at the correct time. I still go back to the CPS and wonder how you checked it? Did you remove and clean it or simply meter it? It's just a Hall effect switch but may switch intermittently if the sensor is fouled.
 

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Discussion Starter #19
I already heard about some sprint not starting because of that sensor. I don't think the guy tried w/ starting fluid though. Worth trying though.
A good indication would also be the values when trying to balance the throttle body. They shouldn't be realistic. That's the same sensor.
A bad sensing of the strokes when starting would result in injecting on the wrong one while cranking.

As already mentioned the crank position sensor could also be the culprit as it provides a lower voltage signal when cranking just because it's a magnetic sensor (like a guitar microphone). So once started over (w/ starting fluid) thus reaching a higher rotation speed it provides a sufficient voltage peak to peak. But you said you double checked it so... In addition there wouldn't be any spark as well.
But my experience tends to show (mainly on cars) that CPS while not preventing the engine to run OK rends the starting erratic and difficult until it's completely shot.

Thanks fredsprint. The only way to eliminate this possibility would be to replace the sensor. It would be an expensive exercise to do this with any suspect part ( pump,injectors etc ) but that may be the price you have to pay for DIY. When I checked the sensor, I put my digital multimeter across the sensor (basically a induction coil of wire ) and it read 560ohms from memory which is what it is supposed to be from info picked up on the forums. I also put my meter on volts and swiped a spanner across the sensor and it registered the induced voltage milli volts. Cant remember what it was but it increased as the speed and number of passes increased. Not much else you can measure.?
 

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As mentioned to fredsprint , I removed the CPS and it was clean, tested it with multimetyer to check resistance 555ohms and passing a spanner past the sensor will read up to 16 millivolts on AC volts. Its actually a 2 wire inductive pick up. There is a 3 wire Hall effect pickup just inboard of this one which is the speed sensor I think.
Tried starting with a car battery across the bike battery, no difference. Does anyone know what controls the mixture on this machine. I would like to eliminate the possibility of it being to lean a mix on start up. It would be nice to have an ECU connector pin out diagram with explanation of all input and output signals.
Thanks
 
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