Scag Turf Tiger 29dfi problems Please help!

[Mad Mackie]

Adding to the direction that Fish is heading, there is an engine mounted "Y" harness each leg of which connects to the ignition coils. In these legs there is a diode installed and the purpose of these diodes is to prevent cross feeding of the primary coil voltage when the engine is shut down either by the key switch or the safety control module on the machine.
When the key switch is in the off position, it grounds this engine harness and shuts the engine down.
If either diode in the harness is shorted, then some strange problems can happen and get worse on a DFI engine.
Key switches are known to go bad as the coil primary voltage can be 200 Volts or more and this voltage is present in the key switch at all times the engine is running. The key switch can develop and intermittent problem and cause other running problems which react differently on a DFI engine as compared to a carburetor engine.
Just some thoughts!
Mad Mackie in CT

 

[Fish]

yeah, the unplug thingee is a good tool too, as I have seen a lot of twin engines run pretty good until they get into some grass, and it turns out that the engine is only running on one cylinder.

The greatest thing about my suggestion, is that it is free to try/test, and it narrows down the problem quickly...

 

[turftiger13]

yeah, the unplug thingee is a good tool too, as I have seen a lot of twin engines run pretty good until they get into some grass, and it turns out that the engine is only running on one cylinder.

The greatest thing about my suggestion, is that it is free to try/test, and it narrows down the problem quickly...

I totally agree with everything you are saying. Both coils are new and both are firing. I have done this already. My question is if I pull the fuel supply this will not affect the dfi correct? They will still inject the same until the full runs out am I right? If so whatever is telling them how much fuel to inject is sending false info.

 

[turftiger13]

Adding to the direction that Fish is heading, there is an engine mounted "Y" harness each leg of which connects to the ignition coils. In these legs there is a diode installed and the purpose of these diodes is to prevent cross feeding of the primary coil voltage when the engine is shut down either by the key switch or the safety control module on the machine.
When the key switch is in the off position, it grounds this engine harness and shuts the engine down.
If either diode in the harness is shorted, then some strange problems can happen and get worse on a DFI engine.
Key switches are known to go bad as the coil primary voltage can be 200 Volts or more and this voltage is present in the key switch at all times the engine is running. The key switch can develop and intermittent problem and cause other running problems which react differently on a DFI engine as compared to a carburetor engine.
Just some thoughts!
Mad Mackie in CT

i believe you are on the right track. It started but then just kept getting worse. It is a good engine IMO and I truly believe there is nothing wrong internally. It is so frustrating and I cannot wait to get this problem resolved. This is my last season in the mowing business so getting another machine is not an option.