cylinders 1,3,5 on df300 not firing

[awalchli]

have a problem that is driving me crazy: my port side 2008 df300 is only running on 1 bank of cylinders. 1,3,5 are not firing. have hooked up engine to sds and everything seems normal except I have a map sensor pressure detect port blocked alarm. I guess this would happen running on 3 cylinders anyways.

with the sds cutting ignition or fuel injector to cylinders 1-3-5 has no effect on the engine.

what can cause one side of the engine not to fire? looking at the wiring diagrams all the 12+, grounds for coils as well as fuel injectors go to the same plugs.

thanks for your help

[redlowrey]

I would think that your injector grounds would go directly to the ecm, and your five volt ignition module coil switch voltage would come out of the ecm to each coil to switch them on and off. Your twelve volt supply to your coils will come from one plug, injector supply voltage another, and your coil grounds on another plug

It would be possible for the engine to miss on 1 3 5 if the plug where the grounds go were not going to ground, or you were missing the supply voltage to 1 3 5. or you were missing the supply voltage to 135 injectors.

If I was taking a punt I would be looking at the coil grounds plug, you should be able to check all that with a low powered test light or scope, I think an auto electrician would find the problem for you easy.

I am not sure if your engine is grouped or sequential on the injectors eg firing in banks 135 and 246 or the same as the firing order, if they fire in groups it is possible you have fried the driver in the ecm, you can check that with a test light.

Your map sensor signal voltage would be running near three and a half volts with the engine running on three cyls, just make sure you haven't got an air leak on the plenum, because I would have thought that a three cylinder miss whether fuel or spark would make the engine run very rich from the map signal voltage being high.

[awalchli]

ok: checked compression on bank that was not firing and compression is ok. also we checked spark and do not have spark on those cylinders. harness is the same for left and right bank as well as grounds.

swapped ecu from center engine to port and same issue no change. on the sds all sensors are normal except for map sensor 2 (pressure detect port) but is expected with 3 cylinders not firing.

got a suggestion to pull flywheel and check that stator and or magnets are not damaged. this is not clear to me on the df300 are there magnets on the flywheel itself?

thanks,

[redlowrey]

Who ever told you that must only work on two strokes, the only function the stator has is to make ac voltage and current to be rectified by the voltage regulator for battery charging.
Under the flywheel you will see lugs protruding from it, there are thirty four of them with a wider spacing between two, at the centre point of the wide space it will be sixty degree's before tdc. The crank sensor counts these lugs that are 10 degree's between each other and with information from the cam sensors the ecm calculates timing for spark and injection.

The ignition system is full electronic and uses battery voltage to charge the primary windings in the coils, each coil has it's own module built into it and turns on and off from information from the ecm that is why there is three wires going to it, supply, ground, and switch.
When you pulled the plugs was 246 black, and 135 wet, they should have been if you had no spark, the injectors should have been switching.

You need to do some voltage drop testing, are you capable.

[awalchli]

thanks for the reply. unfortunately I am about 2 hours from the boat and can only work on it on the weekend. yesterday I had the mechanic go out to the boat. he had limited time so he will need to go back later this week.

the bank is completely dead, no spark and no fuel. he pulled the injectors and they are not firing he says he has intermittent spark on one of the cylinders but they were dead. signals from cam position as well as crank position sensor do not show a problem on the sds.

we are going to do more trouble shooting on the wiring harness as that is where the problem is pointing. looking at the diagrams of the harness all the coil grounds go to the same plug with banks and the +12V as well.

as suggested we will do voltage drop testing and track down where the problem is.

[redlowrey]

2007 is the latest schematic I have and it shows all six coil grounds going to the plug, but not voltage supply in the same plug they go to a separate plug. What have you actually lost voltage supply or your grounds. With the key on you should have battery voltage on both sides of your injector plugs and battery voltage on all six of the gray wires on the coil plugs.

[Diamondsco]

Did we ever correctly diagnose this problem? I am having the exact same thing happen to my 2007 df 300. No change from interruption on 1,3,and 5 with the SDS.

[awalchli]

no I did not find exacly where the issue was in the wiring harness but it was the harness. we installed a new harness and everything went back to normal. mechanic told me he has changed a lot of harnesses on 2007, 2008 Suzuki 250 and 300's. I have trips on my boat and this is the second engine I had to replace the harness on.