I was reading the post about blow by and reminded me about my 753 that is slow in warming up on one cylinder. It smokes for a couple of minutes no matter how cold it is. If it has been run within 15 min. or so, it does not smoke. It acts like unburned diesel and does not use any oil. This machine has 4200 hrs. on it and seems to start real good. Any ideas on why it is doing this? TRG753
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Have you had your injectors checked? You could have a bad nozzle causing the fuel to cause droplets that will not readly burn. It could be a valve too. I'd start by checking compression to rule out a valve seat problem. Check your valve clearance too.
Thanks Tazza, I will check out those items and see what it might be. Do you think and injector could cause this? Tom
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If compression is good, and oil consumption is minimal, I'd bet on injectors. They can make a otherwise good engine run and smoke like a piece of junk.
Our 3208 Cat at 8800 hours, smoked badly out of one bank / side of the v8 engine even when warm, (dual exhaust). We pulled the injectors and tested them, one was shot, some were ok to so so. Do to the higher hours I was skeptical about this being the cure.
I put 4 new injectors in the "smoky" bank of the engine and took the best of the others and installed them in the "clean" bank.
The end result was now the clean bank now appeared to be the "smoky" side duing warm up. Once the engine came up to operating temp both looked to burn clean now, but it was very obvious during warm up, but now the other side. So I sprang for 4 more injectors the next time the log loader came into the shop, now it run like a engine with 1/2 its hours.
Regards
Ken
With the speed the pistons move when the engine is started there will be more than enough compression to ignite the fuel if the spray is rite. Starting is the hardest part, when its running the compression is very high and the fuel will burn easily.
If you have no bore damage or worn rings i'd bet it was injectors.
I tested a set i had by removing the injectors and fuel lines, i then attached a tube line to number 1 on the injector and attached an injector to it hanging out the back of the machine. I then cranked the engine over and watched the spray pattern, a perfect long mist with no fuel drops on the injector. The spray should be nice and even. This will tell you if the pattern is correct but it will not tell you if it leaks or what the crack pressure is. Only do it this way if you don't want to spend any money and to just check the spray pattern. Remember the fuel coming out can pierce the skin, do not put any part of your body around it when you are testing.
If its an injector problem you really should get it fixed, i'm not sure if its an issue on direct injection engines only or not but i read leaky injectors that make droplets of fuel actually erode the surface of the pistons. It must be something to do with the fuel burning when it sits on the piston instead of a nice fuel/air mixture in vapor form.
What color is the smoke ?-----------the injector may be leaking down ( dripping ) into the cylinder when the engine is stopped and when you start up it is burning the excess off -------- you say you don't have oil consumption so I would not think it's the valve guides as this is another way it smokes on startup , when you kill the engine oil leaks past worn valve stem guides and seals into the cylinder or on to the top of the valve if closed , either way it smokes on start up , a bad nozzle tip will dump the fuel into the cylinder and not atomize it ( break it down to smaller particles ) into a vapor which in turn doesn't burn as efficently , the unburned fuel sticks to the walls of the cylinder and makes the cylinder , piston and rings very wet and dilutes the oil lubrication the walls which cause wear faster and I would think it would lower the compression a little being the diesel is not as thick as the oil , ever notice when you do a wet compression test the compression is higher when oiled ------------ on a seperate note I had a Chevy 350 in a truck that had some bad valve stem seals and was smoking heavy on start ups and using 2 quarts of oil per tank , I put some of that Rislone ring sealer in it and lowered the comsumption to 1 quart every two tanks to 3 tanks untill I found time to swop the heads about 2 years later , kinda like a bandage for a machette cut but will keep you in the game
Thanks guys for the help! I will bet that you guys are right. No excess oil consumption is noted and the smoke is more of a white smoke and acts like excess diesel fuel that leaked into the cylinder. How would be the easiest way to tell which cylinder or injector would be bad? Maybe take them all out and have them tested or how much would a new set of injectors cost? I have no idea on how many hrs. these injectors have on them. The machine has a little over 4200 hrs. on it. It starts OK in the cold, but I did install a soft plug heater on it this winter.
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Most injection pump shops will test for a nominal fee, this gives you the advantage of knowing if the injector holds back the fuel flow until the "crack" pressure is reached. Although you can do as Tazza say and remove the injectors hook them back to a injector line and crank the engine to see how fine of a mist each makes. Should be uniform, no drops or streams of fuel. The ones that are in poor shape will be fairly obvious, leaking, dripping, goofy spray patterns
For my Kubota d950 (553 bobcat) they were @ 65 usd each at a kubota engine parts dealer.
Ken
Thanks for the info. On the injectors, how critical is it when replacing them to get everything torqued down just right? Also, do you think that the No. 1 cylinder which I would guess is on the front of the engine, opposite the flywheel may be the culprit? I talked to one guy today that thought it might be the front clyinder. Slower to warm up! Anyway, I may just have to buy 4 new injectors and get a better pattern going to keep from doing some damage. Any other ideas would be appreciated. You guys have great ideas. Tom
It sounds like an injector problem IMO. If that #1 injector is not "cracking" but is just leaking it will cause that cylinder to be cooler and it will also produce your smoking issue created by the unburned fuel in the exhaust system. I would also recommend that you look into have your injectors rebuilt verses buying new ones. It is usually a lot cheaper to get them rebuilt.
Number 1 is at the front of the engine, where the water pump and alternator are located.
I can't even say you can tell by the smoke if you removed the exhaust manifold. Especially if its an east/west facing machine.
As for torque, i haven't found this to be an issue, ONLY tighten it by the body, not by the part that holds the internals in, remove the tap off fittings and use an extended socket to tighten it up. Install new copper washers, these should be supplied with the injectors. Replace the tap off banjo fittings and aluminum washers and nut, install the the tube lines and you should be set.
As for the injector pump, you would need to take it to an injection shop, they can attach a gauge to check delivery pressures and that the valves are working correctly. This is all done on the machine, don't remove the pump!. If its smoking i'd suspect the injectors before the pump, if the pump was going i'd expect lack of power but not excessive smoke as fuel delivery would be lower than it should be. But i am not a diesel mechanic.
Personally i'd clean around the injectors by un-doing them a few turns and then blow the junk out from around them with compressed air. Finish removing the injectors and delivery tubes. Attach the shortest tube to number 1 on the injector and put an injector on the end of the tube. Keep it pointing down and away from you and get someone to crank the engine over. Check the spray pattern, repeat for the other 3 injectors. Remember the tip of the injector shouldn't have any droplets on it, thats a sign of leakage and the injector needs a re-build. Only crank the engine for small bursts, like no more than 20 seconds and let it cool. There won't be a lot of load on it, but still go easy on it.
Keep where the fuel injects into the injector as clean as possible, the tap off section isn't as critical but keep it as clean as you can.
I pulled down 4 sets of injectors and cleaned them up and tested them this way, they ran sweet as, no smoke at all, not even at startup!!!. If you pull them down, do only 1 at a time, never mix parts from different injectors up. Be careful not to damage the nozzle on the injectors, they are very fragile. If you need any help just give me a yell.
Thanks Tazza, I talked to another guy yesterday about injectors and he told me a little trick. For cleaning around the injector hole, he told me to do what you said and also said take a piece of hydraulic hose (1/2" approx.) and remove the rubber around the hose near the end of the hose. Then fray the wires in the hose and use the wire end of the hose to clean up the surface where the copper rings seats. He said this works great! Tom
Tazza, I pulled out my injectors and sent them down to Diesel Tech and they said they never saw such worn injectors. They rebuilt them in about 2 days and I will be installing them shortly and I will let you know what the outcome is. Hope it helped!!!!!!!!!
If they were in such bad shape it should run like a dream with the new nozzles.
