966f performance question

komatsukid · Oct 29, 2007

Hi Guys,
I have been running a 966f series 2 loader for almost two years. When I got put in the machine they just got it back from Michigan Cat the engine got week so they rebuilt it. The first thing I noticed when I started running it was it was weak on power it would only hold about 2000 rpm through a simulated torque stall. Cat came out and turned the fuel and air pressure up after that it seemed to be better until now, when i put a load on the engine, like digging in a hard bank or climbing a steep grade the engine missfires, and blows black smoke and soot like crazy and the turbo doesnt seem to spool up. Any ideas what might be causing this?

Ross · Oct 29, 2007

Could be a number of things really.

Check the air-filter. (Run without it in for 5 mins)

Pull the intake rubber off and check the turbo is OK

How does the machine perform under no load? Does it start, stop and tick over ok?

If not then get CAT back on the job.

Ross

jperfect · Oct 29, 2007

off the the subject for sec. what part of michigan and who are you working for?

Squizzy246B · Oct 30, 2007

IIRC I had a similar problem on a 950F, it was the rubber air inlet piping collapsing when the air filter got slightly restricted and the machine was hot. It would not do it when the machine was cold. I also believe we had to do the turbo up shortly after that.

RonG · Oct 30, 2007

Sounds like an exhaust manifold leaking.It is pretty common on Cat engines.Ron G

komatsukid · Oct 30, 2007

I start the machine and let it warm for about 30 min before running it. It makes the noise all day. I noticed something else not right today, the idel rpm is at 950 revs per min. we have another identical loader, and it idels at about 600 rpm. Anyway I looked at the turbo today the impellar shaft is tight and the compressor "fins" are not damaged. Turbochargers run on exhaust pressure, if the engine is not firing on all six pistons could this cause turbo lag?

surfer-joe · Oct 30, 2007

I'd venture to say that the timing is not correct. Ross is right, get Michigan Cat back out and tell them you want a competent hand to go thru the fuel system.

Good Luck!

komatsukid · Nov 2, 2007

Cat was here today to look at my loader. The field mechanic and I worked on it for almost the entire day. The first thing we did was check boost and fuel pressures. Both these checked out above normal. Then we moved to the torque converter, this checked out perfect. Next we checked the timming this also was fine. We then decided to adjust the valves, three out of the six cylinders were so far out of adjustment we could nearly slide a pencil between the valve and the rockerarm. Belive it or not adjusting the valves cured 50% of the problem. We then jerked out the injection nozzels and replaced all six of those. After that it was about 75% cured. Finally we "lapped" the injection pump check-valves that shoot fuel to each nozzel. That did it! The ol girl runs like a bat out of hell now!!!

anyway just thought you guys might like to know what we did to fix it.

Ross · Nov 2, 2007

Well defo not a quick fix job.

We then decided to adjust the valves, three out of the six cylinders were so far out of adjustment we could nearly slide a pencil between the valve and the rockerarm.

Should have sounded like a Bag of hammers in a washing machine

We then jerked out the injection nozzels and replaced all six of those.

Woo well that would have broke the bank i recon?

Finally we "lapped" the injection pump check-valves that shoot fuel to each nozzel.

Didnt think you could lap the delivery valves in on them pumps? Well learn summit everyday.

anyway just thought you guys might like to know what we did to fix it

Yeah thanks for sharing. Glad the machine back up to speed. Any pics wink wink.

Ross

Wulf · Nov 2, 2007

How many hours on the rebuild KK... also what model of engine is used in your 966F?

The need to replace all 6 injectors and mess with the fuel pump check/delivery valves (I'm with Ross on never hearing of this before

) would indicate low fuel quality or contamination.

Why were the valve clearances so far out? I would be very concerned that the overheads or camshaft lobes were wearing

komatsukid · Nov 3, 2007

There is about 3 thousand hours on the rebuild. The mechanic said the valves should have been inspected/adjusted at the first oil change. I never thought to ask him if the camshaft could have sustained damage due to the rocker arms being so loose. The engine model is 3306. The reason we went into the pump was to eliminate the posibilty of the delivery valves leaking. I have never done this, But he explained to me that if the valves get a "scaling" formed on them fuel will leak down from the injection line. Every time the pump shoots fuel to a nozzel it has to prime the injection line.

Ross · Nov 3, 2007

Never really had much bother with 3306 engines apart from a few piston ring epidemics and total loss on high hour machine (Graders)

The mechanic said the valves should have been inspected/adjusted at the first oil change.

This is careless on CAT's behalf as they should have insisted on this service as part of the warranty and charged handsomely for it including a PDI rebuild report.

I never thought to ask him if the camshaft could have sustained damage due to the rocker arms being so loose.

Quite possible but the problem wont rear its ugly head for a while. A clock work tick will spell trouble.

The reason we went into the pump was to eliminate the posibilty of the delivery valves leaking.

I have encountered pump delivery problems with 3406 engines but not the 3306. Mainly the metering sleeves (When worn) which can reduce the injector pressure to the injectors. This problem can only be cured by sending the whole pump off to a specialist.

Ross

Wulf · Nov 5, 2007

komatsukid said:
There is about 3 thousand hours on the rebuild. The mechanic said the valves should have been inspected/adjusted at the first oil change. I never thought to ask him if the camshaft could have sustained damage due to the rocker arms being so loose. The engine model is 3306. The reason we went into the pump was to eliminate the posibilty of the delivery valves leaking. I have never done this, But he explained to me that if the valves get a "scaling" formed on them fuel will leak down from the injection line. Every time the pump shoots fuel to a nozzel it has to prime the injection line.

I guess its out of warranty then?

Based on my experiences with reman engines the valves should have been adjusted at the rebuild shop when the engine came off the dyno as part of quality control process. Clearances can tighten up initially, if the valves recede slightly but after initial set everything should be good for a very long time.

If the valves were so loose at just 3000 hrs something must be wearing prematurely such as cam bearings, lobes rockers or something?:beatsme

CatYelloBlooded · May 6, 2008

A pencil in there? Wow- I'd say that had a little to do with it. When you say they checked the timing, You mean they pinned her at the flywheel and on the pump? Does that engine have a timing advance? In mossville engine plant the engines aren't timed with pins, but flow timed. An instructor showed me this and i'll never pin time it again. What i'm referring to is locking the pump and adjusting the engine relation to it. In the factory they advance the engines slightly to get the power they need at the dyno. If you find a mechanic locally who can do this for you she'll still be in spec and your fuel economy will stay the same; but it'll run like a striped a** ape. Brings an old DITA to life.

komatsukid · May 6, 2008

i have heard of cat advancing the timing but i dont recall the degrees. last year when cat was working on that 966 we checked the timing using the pins. it was spec.

w2bstoned · Jun 11, 2008

How many hours did they get on the motor before a rebuild? I have 14000hrs and still original, It only uses three quaters of gallon of oil per tank of fuel

komatsukid · Jun 11, 2008

i dont know how many hours were on the engine prior to rebuild. as of today the loader has 21004 hours on it.

John C. · Jun 11, 2008

I don't remember if that engine has hardened rocker arm tips but I thought it did. Anyway the only engine I've found sensitive about needing rocker adjustments is the Cummins B and C engines. The rockers are soft and the valve stems actually wear divots into the ends.

I put a few 3306 engines together and went multiple thousands of hours before readjusting. I would say if they were that bad there was something done wrong at rebuild.

w2bstoned · Jun 15, 2008

Komatsukid yours burning much oil? How is the loader holding up after all those hours?

Ray Welsh · Jun 15, 2008

w2bstoned said:
How many hours did they get on the motor before a rebuild? I have 14000hrs and still original, It only uses three quaters of gallon of oil per tank of fuel

That oil consumption seems kinda high for a 3306. I have had a few and when they started to drink oil like that, I'd change the oil. Then they would use none for a couple of weeks. 14000hrs is a good indicator for a rebuild, although many will go longer. Hard work is the key to long life of 3306 and remember not to idle them for too long.
I always used straight 30 oil which had a wider working range than multigrades..........C ya........Ray

966f performance question

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