Bobcat 743 issues with one Cylinder not firing

[SaltyOlive]

Hello, Yesterday I was grading with the 743 and it just turned off....after some investigation I found the tank hose had cracked off .... I replaced the hose, opened the bleeder on the injector pump area, pumped the bulb a few times, closed the bleeder, pumped the bulb till tight, turned on the glow plugs for 12 sec, and she started with a little struggle, a lot of black smoke and appeared to be running on 3 of the 4 cylinders, I cracked each injector and a small amount of air was released and at the same time found it was the cylinder closest to the cab that was the culprit....in the past year I've had a little issue at start up with one cylinder seeming like it needed to warm up, but then it would run great....today that one cylinder did not smooth out after warm up and I'm not sure if it's bad rings or injector .... for the most part it did not smoke at idle, but load on it, more subtle white smoke....and what seemed like a slight stale fuel smell....I did not check cylinder compression as I am new to diesels and did not have an appropriate gauge....any help would greatly be appreciated... Thank You

 

[Tazza]

I'd suspect the injector first. You can always swap the injector with another one and see if the issue moves.
I have done a redneck injector test before. Pull the injectors out, hood up a short tube line to the injector pump so you can hook an injector to it and watch the spray. Get a helper to crank the motor and watch the spray pattern. It should be a narrow cone and no drips on the tip of the injector. Do this with all injector sand see if any are different. You said number 4 doesn't seem to run right, hopefully it's different to the others, then you know what it is.

 

[SaltyOlive]

I'd suspect the injector first. You can always swap the injector with another one and see if the issue moves.
I have done a redneck injector test before. Pull the injectors out, hood up a short tube line to the injector pump so you can hook an injector to it and watch the spray. Get a helper to crank the motor and watch the spray pattern. It should be a narrow cone and no drips on the tip of the injector. Do this with all injector sand see if any are different. You said number 4 doesn't seem to run right, hopefully it's different to the others, then you know what it is.

Thank You Tazza, That is a great way to quickly diagnose the injector....I do have them in order coming in, but today I'll swap them and see if the problem occurs in the swapped cylinder.... I'll keep ya posted....

 

[buckwill]

Thank You Tazza, That is a great way to quickly diagnose the injector....I do have them in order coming in, but today I'll swap them and see if the problem occurs in the swapped cylinder.... I'll keep ya posted....

whi te smoke in the exhaust usually means the fuel is not burning correctly due to not enought heat in the combustion chamber, this is usually due to not enough compression or injector tip breaking,, it sounds as if that cylinder has been failing for some time or some other event in the engine, what u can do is take a propane torch and put heat right into the open manifold mebbe bring it up to heat, if it picks up the cylinder then send yr tips to an injector shop, have them tested and repair/replace the bad ones, as last poster suggested moving injs to another cylinder will identify which one is bad, if the miss follows then repair/replace the inj, good thing to do while u have the inj out is do compression tested not just on lazy cyl but on all, have fub, let us know, buck

 

[buckwill]

whi te smoke in the exhaust usually means the fuel is not burning correctly due to not enought heat in the combustion chamber, this is usually due to not enough compression or injector tip breaking,, it sounds as if that cylinder has been failing for some time or some other event in the engine, what u can do is take a propane torch and put heat right into the open manifold mebbe bring it up to heat, if it picks up the cylinder then send yr tips to an injector shop, have them tested and repair/replace the bad ones, as last poster suggested moving injs to another cylinder will identify which one is bad, if the miss follows then repair/replace the inj, good thing to do while u have the inj out is do compression tested not just on lazy cyl but on all, have fub, let us know, buck

the propane torch thing is with putting heat into a running engine not a stopped one, just a clarufication

 

[SaltyOlive]

the propane torch thing is with putting heat into a running engine not a stopped one, just a clarufication

Hey Buck and Tazza, It took a little time to get back to the project, but I did as Tazza stated and began taking the injectors out and decided to just replace with cheaper ones off eBay as a trial....I replaced the two in question bled the system and it started right up and ran perfectly....very little smoke at start up and then clean and clear through all use for a few hours....I suspect that having the bobcat in a cold climate for years and starting it only every once in a while and then moving it to a warm climate with more use, I prob fouled up the tips with carbon in the cold climate....that was a great idea buck to have them rebuilt as bobcat charges $220 per injector....would you know of a good place to have them rebuilt?

 

[buckwill]

Hey Buck and Tazza, It took a little time to get back to the project, but I did as Tazza stated and began taking the injectors out and decided to just replace with cheaper ones off eBay as a trial....I replaced the two in question bled the system and it started right up and ran perfectly....very little smoke at start up and then clean and clear through all use for a few hours....I suspect that having the bobcat in a cold climate for years and starting it only every once in a while and then moving it to a warm climate with more use, I prob fouled up the tips with carbon in the cold climate....that was a great idea buck to have them rebuilt as bobcat charges $220 per injector....would you know of a good place to have them rebuilt?

most any competent injector shop can clean those tips, i live 145 miles from bakersfield so i send stuff ,dthere,depending on yr total hours, id imagine yr tips just need a good cleaning, if u tell me where u at i wud be happy to find a shop near u to do some cleaning, also, if yr back up to snuff again d suggest u dose it up good with lucas fuel treatment, dont use gasoline fuel inj cleaner use diesel specific fuel inj, just follow amounts called for but dose it up heavy now and periodically afterwards,,,,u can build yr own inj cleaner tester with the pump section of a hydraulic porta power, just load it with fuel instead of hyd fluid, and of course the appropiate pipe and fittings for yr injectors, u beed also a guage in there so that u can see cracking pressure, ive saved many junkyard "BAD" injectors with this setup, have fun, let us know, today dec 22 is my birthday, im 71 years old, and of coarse the things i tell others to do and done myself, i can only talk about instead of do, llike putting 2 crankshafts over my shoulder and walkinf off, today id do good to pick up one piston, doc says no more than the weight of my plate or sandwich, how i do ramble

 

[Tazza]

most any competent injector shop can clean those tips, i live 145 miles from bakersfield so i send stuff ,dthere,depending on yr total hours, id imagine yr tips just need a good cleaning, if u tell me where u at i wud be happy to find a shop near u to do some cleaning, also, if yr back up to snuff again d suggest u dose it up good with lucas fuel treatment, dont use gasoline fuel inj cleaner use diesel specific fuel inj, just follow amounts called for but dose it up heavy now and periodically afterwards,,,,u can build yr own inj cleaner tester with the pump section of a hydraulic porta power, just load it with fuel instead of hyd fluid, and of course the appropiate pipe and fittings for yr injectors, u beed also a guage in there so that u can see cracking pressure, ive saved many junkyard "BAD" injectors with this setup, have fun, let us know, today dec 22 is my birthday, im 71 years old, and of coarse the things i tell others to do and done myself, i can only talk about instead of do, llike putting 2 crankshafts over my shoulder and walkinf off, today id do good to pick up one piston, doc says no more than the weight of my plate or sandwich, how i do ramble

Happy birthday
Injector cleaner is a good idea, sadly most people resort to using cleaner when they are already too far gone to make a really bad one good again, if it's a little dirty/sticky it can fix it though.
Keep up the good work with passing on your knowledge.

 

[reaperman]

most any competent injector shop can clean those tips, i live 145 miles from bakersfield so i send stuff ,dthere,depending on yr total hours, id imagine yr tips just need a good cleaning, if u tell me where u at i wud be happy to find a shop near u to do some cleaning, also, if yr back up to snuff again d suggest u dose it up good with lucas fuel treatment, dont use gasoline fuel inj cleaner use diesel specific fuel inj, just follow amounts called for but dose it up heavy now and periodically afterwards,,,,u can build yr own inj cleaner tester with the pump section of a hydraulic porta power, just load it with fuel instead of hyd fluid, and of course the appropiate pipe and fittings for yr injectors, u beed also a guage in there so that u can see cracking pressure, ive saved many junkyard "BAD" injectors with this setup, have fun, let us know, today dec 22 is my birthday, im 71 years old, and of coarse the things i tell others to do and done myself, i can only talk about instead of do, llike putting 2 crankshafts over my shoulder and walkinf off, today id do good to pick up one piston, doc says no more than the weight of my plate or sandwich, how i do ramble

Happy birthday. Buckwill. You may be limited on what you can carry these days. But the knowledge you can pass on weighs tons! Keep it up, were always learning from others.