Engine running rougher when warm - TN75F

[svcguy]

I have found that my TN75F starts and runs beautifully when cold. Once warmed up and operating, it starts to run rough at about 1500 rpms and up. I have checked the valves and all are within specs. At low rpm it is perfectly smooth. When under load, it is always smooth, but if no load or really light loads @ 1500 and more - it runs rough. I am thinking perhaps injection pump timing?

 

[Jbrink64]

It probably is timing. It's fine when cold, so the base timing is ok. I'd bet the cold advance isn't working. It could be a wax motor that heats up whe 12 volts is supplied, or a solenoid that's wired to a temp switch. Both styles are used on these engines.

 

[svcguy]

Thanks, wasn't familiar with that, I will take a look.