How can I tell which cylinder isn't firing?

[Domush]

I really think my tractor isn't running on all cylinders.. in the literal sense!

As many here know, I have a 336D I recently restored. Well, I'm convinced one cylinder isn't firing (or getting fuel, not sure which). How can I find out which cylinder, if any, isn't firing and if it is fuel related or compression related?

I'm a bit scared of toying with a diesel engine while it is running, given the pressures involved and could use some sage advice from the experts here.

Once the temps here improve a bit, I'll try and get a video of the engine running, so you can all hear what I'm hearing when it is running. It just sounds like it is running on 2/3 cylinders, and the constant stream of wet smoke out the tailpipe only hardens my distrust of this engine.

Thanks a bunch!

 

[winston1]

If you don't want to loosen while running you might consider this. Testing Injection Pump and Injectors

 

[Domush]

If you don't want to loosen while running you might consider this. Testing Injection Pump and Injectors

Thanks for the link, winston.

I don't mind doing normal diagnostics which others have done and survived. I simply want to make sure I'm not going to kill myself (or the engine) by knowing exactly how to do it and what to do if everything goes pear shaped while I'm doing it.

I'm guessing you mean loosening the fuel lines at the injectors one by one and listening for the engine to miss or not miss? Is it that simple? Is there anything I should know before doing it? Any gotchas involved?

 

[Jimbrown]

Well the way aircraft mechanics do it is to take a china marker (grease pencil) and make about a 1/4 inch dot on the exahaust manifold right out of each cyinder and the one that does not burn off right away is not firing. Works on race car also.

 

[Domush]

Well the way aircraft mechanics do it is to take a china marker (grease pencil) and make about a 1/4 inch dot on the exahaust manifold right out of each cyinder and the one that does not burn off right away is not firing. Works on race car also.

Sounds like a good method, but I'm pretty sure this exhaust manifold is never coming off. The bold heads barely resemble bolt heads anymore, and that's a project I'm not willing to get into if I can at all avoid it.

 

[284 International]

I'm certainly not an expert, but I've loosened the retaining nut on injector lines while the tractor is cranking and running. Fuel dribbles and sometimes spurts out, but it doesn't come lancing out of the fitting like a laser beam, either.

When I had similar questions about a missing cylinder, I got it running, then cracked the injector fittings with a wrench, and attempted to isolate the missing cylinder. It's kind of like testing magnetos in a plane: You're looking for consistent RPM drop across all three cylinders, and if one drops less than the others, or not at all, that's your troubled cylinder. This won't isolate if it is compression or fuel related, since the wet smoke almost certainly means there is unburned fuel.

Once it's isolated, I would work easy to hard: It's getting fuel, since there is excess smoke. Pull the valve cover and re-check the valve adjustments. Hopefully either the exhaust is hanging open a little bit, or the intake isn't opening, and you can correct it externally by adjusting the valve clearances or whatever else is amiss. If you can't detect any issues there, you're stuck buying or renting a compression tester and going that route.

As a bit of encouragement, my 2 cylinder YM240 would run on a single cylinder, so I would imagine a 3 cylinder would run less poorly be more functional with only 1/3 of its cylinders disabled rather than 1/2. On mine, it was missing a rocker arm retainer that kept the rockers on their shaft. California, Winston1, KenMac, Gary Sweat, NormDe2001, Bowinelk, Car Doc and others spent hours walking me through the process of isolating and resolving that, and other issues. They enabled me to get my basket case YM240 operable, and I'm still thankful for their help. Thanks again, guys!

Domush, hopefully we can get the same happy results for you!

 

[SPYDERLK]

Well the way aircraft mechanics do it is to take a china marker (grease pencil) and make about a 1/4 inch dot on the exahaust manifold right out of each cyinder and the one that does not burn off right away is not firing. Works on race car also.

Sounds like a good method, but I'm pretty sure this exhaust manifold is never coming off. The bold heads barely resemble bolt heads anymore, and that's a project I'm not willing to get into if I can at all avoid it.

Great method. To allow you to go a bit further you can get an inexpensive Infrared Thermometer from HF that will serve for many other things as well. I think they go to 600F or more and would be good for comparing cyl temps for, at least, light loads. :thumbsup:
larry

 

[Skyco]

Great method. To allow you to go a bit further you can get an inexpensive Infrared Thermometer from HF that will serve for many other things as well. I think they go to 600F or more and would be good for comparing cyl temps for, at least, light loads. :thumbsup:
larry

Beat me to it! I bought an IR thermometer gun years ago when they cost 10X what they do now...just for the purpose of checking cylinder balancing on a diesel. Of course I've found 100 uses for it since then..one good one is to shoot tires on the trailer and truck when towing, at stops etc, can spot a low one real quick, and also shoot the trailer hubs to spot one running hot.

 

[Domush]

Beat me to it! I bought an IR thermometer gun years ago when they cost 10X what they do now...just for the purpose of checking cylinder balancing on a diesel. Of course I've found 100 uses for it since then..one good one is to shoot tires on the trailer and truck when towing, at stops etc, can spot a low one real quick, and also shoot the trailer hubs to spot one running hot.

I'll be sure to order up one of those tonight. Sounds like a good method of diagnosis. I'll also try loosening the lines and see if there is the same change on all three. Hopefully tomorrow will be warm enough to play around with it.

 

[runningbird]

did you try the grease marker? you don't need to take off the exhaust manifold.