I have a Thruxton that refuses to start. It turns over, there is spark, but injectors are not opening. Using another Thruxton to switch parts. Have switched ECU, gas tank, crank position sensor, all relays, throttle body. I have check the wires coming into the injectors. They read 12.2V, but will not light a 12v LED. Checked current and it’s about 0.04A. Anybody have an clue as to what is happening? My guess is a short that is drawing off current, but where?
The +12 Volts are always present at the Brown/pink wire to the injectors. To fire them the ECU "grounds" the other 2 wires (yellow/pink and yellow/purple) in turn, i.e. allows the connection of the negative -12 Volts to each injector for a few miliseconds as it needs it.
The technique is common in the automotive world and it's called "negative switching".
I've never done that measurement myself, but a digital multimeter is not fast enough to follow the injector's pulse, that is the time the ECU energises them. At idle it's only around 2.7 milliseconds or so. Only an oscilloscope could display that.
I have 2014 Thruxton also. Been swapping parts. I think I have swapped everything but the harness. Rather than swap that, I am getting one off EBay for $80. Let see if it fixes the issue.
You can't swap out the ECU of a 2010 for a 2014 since the 2014 uses CAN bus and won't let the engine run without the electronic speedo anyway. Also, how would you get the speedo to actually work without the sensor in the gearbox? It would make more sense to use the 2010 as a donor bike for the 2014.
Its sounding like the swapping of parts has landed you in a bit of a mess (I know, I could be wrong or misunderstanding something here), but my advice to you at this time would be to put everything back to original and instead of the harness, put your $80 towards a used ECU. There should be a sticker on the ECU and for a 2010 model I think the base map number is 20187.
Checking to see if the ECU is firing (temporarily grounding) the injectors can be done with a 194 bulb, common dash, or marker light on older cars available at any auto parts store. The 194 bulb doesn't have a metal base but two small wires to make contact in a bulb holder. Straighten the contact wires on the bulb and plug them into the connector that plugs into the injector. Crank the engine over and if all is well the bulb will pulse, indicating it is being switched on and off by the ECM.
I'm just wondering how this fault started, you may be able to gain some clues from the circumstances, you seem to be throwing a lot of parts at a bike that just happened not to start one morning, is there more to it than that?
good suggestion above about putting everything back to standard and maybe having a rethink, you can get lost if you change too many parts.
Actually, I picked this up cheap as a non runner. Not sure of the history, but it’s had the air box removed. But other than that it is pretty stock. It may just end up a parts bike for my other one.
The wiring loom for the Right hand cylinder MAP sensor is clearly marked with red tape. Check that.
Right cylinder is when viewed from the top or seated on the bike. The manual calls it Nº2 cylinder.
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