# 08 brute force 750 injectors not firing



## drewski1126 (Jan 4, 2018)

So I picked up a brute the other day and the guy o bought it from wasn’t sure what was wrong with it. 
So after checking the basic things like plugs for spark, fuel pump for pressure and flow test, vehicle down sensor, all the fuses and each connection I’ve come to a dead end. I’m thinking it’s the ECU but I wanted to see if anyone else had any thoughts on it. 

I can add fuel with a squirt bottle to both throttle bodies and the bike will run for a minute until I stop squirting fuel in there. 

All the test have been performed with a new battery fresh charge. 
Vehicle down sensor- reading 1v back to the ECU
Crankshaft position sensor tested good- 425ohms
Fuel pump flow test-2.5 oz in 3sec,
Still need to do then pressure test on it
Injector supply voltage is good -12v for 3sec then 0
Tested them with them off the bike and they will spray fuel with 12v 


Not sure what else it could be besides the ECU
Any thoughts on what would keep the injectors from firing. !? 

Thanks in advanced. 



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## NMKawierider (Apr 11, 2009)

I would think its either the ECM or the CPS...and you tested the crank sensor. How about the throttle position sensor? )8s have a history of bad fuel pumps and ECMs so do check that pressure.


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## drewski1126 (Jan 4, 2018)

NMKawierider said:


> I would think its either the ECM or the CPS...and you tested the crank sensor. How about the throttle position sensor? )8s have a history of bad fuel pumps and ECMs so do check that pressure.




Thanks for the input. Yeah I did check it out as far as the resistance test. Not sure if there’s another test I can do that’s in the manual. I’ll have to check the TPS in the morning when I get off work. As well as the fuel pressure. 


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## drewski1126 (Jan 4, 2018)

All right so I did some digging and I came up with a bad TPS. Ran all the tests in the manual and it failed all of them. Also I checked the Wiring to the sensor and it was good from the ecu. 

My question is now, it states in the manual, to buy a new throttlebody assembly if the TPS is bad. Do I really have to spend that much money, or can I buy the sensor separately


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## NMKawierider (Apr 11, 2009)

Boy..you got me. I know these are set at the factory and some say that's critical with the new systems...but if one could just get the sensor ..and play with it until it ran at least close to what it should..I think I would have to try. First-see in you can get just the TPS...anywhere.

*
UPDATE: I just looked it up. You can just get the TPS by itself. #21176-0100. It is $113.37. though.
But that beats the 600 bucks for the TBs. *


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## drewski1126 (Jan 4, 2018)

Ya that sounds right for the price on a new sensor. 
I went back and double checked it again and it turns out the sensor is good I have my meter on the wrong setting. 

But in the meantime I have checked the wiring harness and every sensor related to the DFI system seems to have good continuity. I need to do a few more tests on some of the sensors to be sure that the ECU is suspect. 
Will update when I have time to do so


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## drewski1126 (Jan 4, 2018)

Thinking about buying a copperhead ECU by velocity devices instead of the stock replacement, If it ends up being the ECU. 

Anyone have any input on the copperhead ECUs


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## drewski1126 (Jan 4, 2018)

(Update)

So I went through and finished testing all my sensors in the Dfi circuit and everything checked out to be on par with the standards in the manual. So with all the test I’ve run on the wiring and the sensors, I’m about 95% sure the ECU is the problem on the bike. 

One thing I’m kinda wondering about in the manual though has me thinking something is backwards with how the standards are supposed to be. 

It states:
ECU Power Source Inspection Meter Connections:
Between Terminal 8 (W) and Battery (–) Terminal
Between Terminal 13 (BR) and Battery (–) Terminal 
Ignition Switch OFF:
Terminal 8 (W): 0 V
Terminal 13 (BR): Battery Voltage Ignition Switch ON:
Both: Battery Voltage

Well with the key on I get batt voltage at both wires like it says, but with the key off, I’m getting the opposite of what it states.(12v at terminal 8 and 0v at terminal 13)

Could someone check this on their 750 and see what you get. I’m curious to know if this is just confirming the ECU being bad. 

Thanks


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## drewski1126 (Jan 4, 2018)

Bump


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## drewski1126 (Jan 4, 2018)

(Update)

So I feel like a real idiot right now. ?

So last night at work I got to thinking about the vehicle down sensor. I had tested it before and got .9 V at the terminals on the switch, Which led me to believe the sensor was good. So I figured I would go ahead and this morning check the voltage at the EC you and see what it was. Well I was getting 4v, Which in the manual states that’s what it should be in the tipped over position. So I figured I would swap it out with another sensor that I just so happen to have on my KX 250 and see what I get.
Well I get .5 V at the EC you and at the sensor with the KX 250 sensor plug down in the bike Cranks right up. 

Me having the sensor taken apart I was taking the voltage read out at the terminals where it plugs in to the harness not on the other side of the harness. And I failed to check at the EC you prior to this morning. 

Thanks for the help everyone. 

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