Diesel runs rough/dies under load

[petebert]

Tractor is a Zetor Zebra 3520, 3 cylinder diesel. It's always had an issue where sometimes under load it would lose a lot of power and run rough. To remedy it I could usually just put everything into neutral, let the motor build back up and then go again. It's gotten worse lately, so much so that it stalled multiple times yesterday while I ran the brush hog. Yesterday when the idle would drop off or it would stall I could pump the primer on the side of the injection pump and the idle would smooth out. The fuel filters are good and fuel is making it to the filters. As of right now it won't start at all.

Here's a video showing the rough idle, notice the black smoke while this happens.

 

[TractorTech]

Have ever pulled the lift pump to see if the cam lever on the pump is not worn or bent? Might replace the lift pump anyway.

 

[petebert]

That is a good idea except it's really hard to find parts for this weird Indian made tractor. And correction the primer is on the lift pump, not the injection pump. I've been able to get it run better if I pump that while it runs but now I can't get it to start even if I pump that. There does seem to be pressure building in the fuel filter canister because if I loosen the bolt on the bottom the fuel will spray out.

I plan on taking the filter system out of the equation and feeding fuel direct to the pump to see what happens. I'll pull that lift pump if that doesn't do anything.

 

[banjodunn]

G'day check for a filter in the tank or restriction to the pump


Jon

 

[CCWKen]

Loosen the fuel cap and see if it runs better. Maybe the vent is clogged. Also, with the cap off, look into the tank while running and see if you're getting a return flow. The flow should increase with rpm. No flow means weak pump and it's not getting enough fuel. The injector pump will produce more fuel than needed by the injectors. The lift pump has to keep up.

 

[topbuilder]

Tractor is a Zetor Zebra 3520, 3 cylinder diesel. It's always had an issue where sometimes under load it would lose a lot of power and run rough. To remedy it I could usually just put everything into neutral, let the motor build back up and then go again. It's gotten worse lately, so much so that it stalled multiple times yesterday while I ran the brush hog. Yesterday when the idle would drop off or it would stall I could pump the primer on the side of the injection pump and the idle would smooth out. The fuel filters are good and fuel is making it to the filters. As of right now it won't start at all.

Here's a video showing the rough idle, notice the black smoke while this happens.

Seems like you are running at too low rpms. 1000 should be minimum for most diesels.

 

[DT86]

1000 should be minimum for most diesels.

Uh, no.

 

[banjodunn]

G'day also check for a filter where the fuel inlet line is into the injector pump some have been known to have a gauze filter on the banjo bolt.
Also is there any chance of some pics of the fuel system might be able to give you some more ideas

Jon

 

[petebert]

I'll take a look in the tank for return and filters. I have a feeling that it could be the lift pump. I'll have to switch over to an electric pump if that's the case since you can't by many replacement parts for these.

 

[DT86]

You can by pass the lift pump too and just gravity feed into the injection pump from a temp fuel container.

You can use anything, a soft drink bottle or a glass jar work well since you only need to run for a few minutes to diagnose. Get some rubber fuel line and a cheap $4 inline filter just to be on the safe side.