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Cub Cadet Fuel in Crankcase

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joepag08
Join Date: Jun 2008
Posts: 11 Valley Lee, MD
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2008-12-29          158900


Cub Cadet 7274 is running good but I've got a slow leak of diesel into the crankcase. The oil level slowly rises, is very thin and smells of diesel. Looking for recommended actions before tearing into it.
Primary I suspect the injection pump. But how likely is it leaking fuel injector? Blowby past the rings would be pitch black, right? What's in there still looks fairly clean/light. Does this tractor have a lift pump? If so, it must not be on the engine block.
If it is the injection pump, can anyone recommend a rebuild service? Thanks for any help you can offer.

Regards,
Joe




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auerbach
Join Date: Sep 2007
Posts: 2168 West of Toronto
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2008-12-29          158904


Head gaskets rarely leak on new engines, but it's a possibility when the oil level goes up, so see if the coolant level goes down during running. If so, drain the oil and see if there's coolant at the bottom. ....


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joepag08
Join Date: Jun 2008
Posts: 11 Valley Lee, MD
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2008-12-29          158908


I ruled out the coolant already. The coolant level was tip top and I drained the crankcase. Definately no water. Whatever it is, it is thoroughly mixed with the oil. BTW, the tractor is about 12 years old (1100 hrs or so).

Thanks,
Joe ....


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candoarms
Join Date: Mar 2007
Posts: 1932 North Dakota
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2008-12-29          158909


Good afternoon, Joe.

I think you've nailed down the problem. The diesel fuel in your oil is likely coming from the injection pump, as it is attached to the engine block, and is driven by engine gears. This would be the most likely source of the problem.

All of this depends on the issue of engine performance. If your engine is running normally, we can likely rule out bad fuel injectors, worn rings, or any other internal engine problems.

I assume you're not using excessive amounts of engine oil, running low on engine power, or noticing any excessive smoke from the exhaust pipe. If this is the case, the diesel fuel in the oil is likely coming from the injector pump.

Being that I live a very long way from you, I wouldn't be able to provide you with the name of a quality repair shop in your area. However, most any auto repair shop would be able to point you in the direction of a dependable shop for which to take your injection pump for a quality rebuild.

Joel ....


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greg_g
Join Date: Jan 2004
Posts: 1816 Western Kentucky
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2008-12-29          158910


That's the 3 cylinder Mitsubishi engine, right? I'm having a hard time accepting leakage through the injection pump drive gears. First, you'd have to have multiple simultaneous seal failures to make a path available into the crankcase. The pump itself has a seal on each piston, then there's the oil seal between the pump and the drive gears, then there's the oil seal between the drive gears and the engine sump. And if the injection pump has it's own lube sump, I'd expect to see diesel fuel in the IP sump too. Then the gear case would have to be at least half full of fuel before it even got to a level where it would leak into the engine sump.

I mean - all this could I suppose be possible - but figure the odds of it all happening at the same time. I'd be more inclined to open the cover on the IP drive gear case and check for fuel. When none drains out, suspect a dripping injector.

Given the info presented this far, I'm more inclined to suspect gravity letting fuel leak past worn rings in a cold engine after it's been shut down for the day. It might have been starting harder than usual for a while, diesel fuel setting on top of a piston head is hard for the starter to compress. And the exhaust smoke upon starting may be taking a little longer each day to go away. But operating heat makes the rings seal better - the tractor probably looked and worked ok after it was warmed up - so you probably had no cause to suspect what else was going on.

//greg// ....


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Murf
Join Date: Dec 1999
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2008-12-29          158914


I'm willing to bet the tractor has to crank a lot more before it starts since this problem arose too right?

It has been my experience that the injectors themselves give up and leak long before any other part of the system.

When this happens the injectors bleed down after shut off and the diesel being as thin as it is seeps past the rings and into the crankcase.

Best of luck. ....


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joepag08
Join Date: Jun 2008
Posts: 11 Valley Lee, MD
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2008-12-29          158921


Yup. 3 cyc mitsu. I'm not an expert so your description of the pump seals is helpful. I should try to open the cover to see if there is fuel laying in there. I have not noticed a significant difficulty with starting cold. In colder weather it starts a little harder but thats normal. Get a puff at startup but not a cloud.

I check the oil each time I use it and it only goes up a little. However, I first discovered this when I was not checking regularly and I thought I had a runaway but it shut down. I pulled the dipstick and there was so much liquid, it was a small geyser spurting out the tube hole. Drained a huge quantity. That seem like a lot for injectors or rings.

I know pump rebuild is in the $300-$400 range. Ring job even more. Would replacing injectors be cheaper? Don't think I want to tackle the pump myself but are there replaceable seals on the injectors? Maybe I could try that first? ....


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earthwrks
Join Date: Dec 2003
Posts: 3853 Home Office in Flat Rock, Michigan
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2008-12-29          158922


errr? $300-400 for an injector pump rebuild? That seems waaaay too low--like double or triple perhaps. I'm jis' sayin' ....


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greg_g
Join Date: Jan 2004
Posts: 1816 Western Kentucky
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2008-12-29          158923


Your problem may only be coming from one injector. I'd start there.

If yours is the glow plug engine, remove all three glow plugs (being careful to keep track of the sealing washers). Disconnect the low pressure line between the fuel filter and the injection pump (so you're not cranking pressurized fuel up the hard lines).

Crank the engine with the starter - don't use the compression release. If cylinder compression blows more fuel out of one injector hole, you have found which cylinder has the fuel lying on top of the piston. That's the dripping injector. If there is no difference among the three, that complicates things. Either a leaking injector isn't the problem at all, or they may all three have started to leak.

//greg// ....


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kthompson
Join Date: Oct 2005
Posts: 5275 South Carolina
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2008-12-30          158926


I am not a diesel mechanic but wondering here:
Is it only the fuel between the injector pump and the injector that can leak or can fuel come through the injector pump or any of the return tubing, just due to gravity, giving the fuel tank as a supply to leak while the engine is off? ....


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greg_g
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2008-12-30          158927


The fuel return line is typically pump driven, and is usually delivered to the tank at or above above the fuel level.

//greg// ....


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kthompson
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2008-12-30          158937


So you only get a little amount per leak down then. How many leak downs does it take to even be a "cup"? If it is run once a week and thus leaks down only once per week, would it leak a cup in a year? Seems hard to think it would. ....


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Murf
Join Date: Dec 1999
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2008-12-30          158938


Quote:
Originally Posted by joepag08 | view 158921
I know pump rebuild is in the $300-$400 range. Ring job even more. Would replacing injectors be cheaper? Don't think I want to tackle the pump myself but are there replaceable seals on the injectors? Maybe I could try that first?


Like EW I'd be very surprised if you could get a pump rebuild for that sort of money. A 'bench test' would cost you that much.

IMHO there is no part of the fuel injection system that can be serviced by anyone but an expert, save a filter or injector change or that sort of thing. Even then it can be tricky, especially the injectors, most go in with a 'crush washer' below them and torque is critical to get a proper fit & seal.

Kenny, the problem is bigger than you think.

I've seen faulty injectors that would leak a 1/4 oz. per shut down.

If this tractor is 12 years old with 1,100 hours on it, that's an average of ~92 hours a year. Since Joe lists his location as Maryland I'm pretty sure he's only cutting grass part of the year. Even with some snow removal, that still looks like a lot of use for a homeowner, meaning fairly frequent use, and so fairly frequent over-night shut downs.

Best of luck. ....


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kthompson
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Posts: 5275 South Carolina
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2008-12-30          158941


Like I said I am not a diesel mechanic or gas for that matter. But Murf using your figures: 1/4 oz per shut down being a large amount (my understanding). So he runs it 92 hours per year but less say only one hour per use so 92 shutdowns. That would be 23 ounces per year, or about 2/3 of a quart. To get a "geyser" it would have to build faster than this or else long long time between oil checks. As EW goes, just saying here.

But if all three injectors are leaking a 1/4 ounce per shutdown and it is 92 shutdowns per year, you would be up to just over 2 quarts per year. Might buy that but still long long time between oil level checks. It does seem he was fortunate that he did not have any run away with that much fuel in his oil. ....


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joepag08
Join Date: Jun 2008
Posts: 11 Valley Lee, MD
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2008-12-31          158954


What a great discussion! This is really helpful. Let me see if I can guide it. I bought the tractor from a landscaper a few years ago. I've only put about 40-50 hours on it. I changed the oil when I bought it. I use short spurts like moving mulch pile or digging a hole. Thats 2-3 extra quarts over about 80-90 shutdowns. That'd be just under an ounce per cycle. Seems alot. But, when I got the geyser thing, I drained the crankcase, and refilled with oil to correct level. From that point on, I check the oil everytime I get on it. In that time, I've only run about 5-6 hours with real short, low rpm runs, about 20 cycles. The stick only shows only about 1/2 cm above full. Maybe 4-6 oz? 5/20= .25 oz. per cycle. Possible injector leakage. That doesn't explain, however, The 1 oz per cycle earlier.

Two things I'll try. I'll runs high rpms for an hour or so and see if that changes the rate. If so would that change the injector theory?
Second, I'm going to send the oil off for analysis just to be sure. Will tell me amount of fuel dilution exactly and whether I'm wearing down metal too. Will post the results.

Joe ....


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earthwrks
Join Date: Dec 2003
Posts: 3853 Home Office in Flat Rock, Michigan
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2008-12-31          158957


Joe amybe I missed it but why are you running low RPM? Modern diesels don't like to be run pretty much under at or near full throttle. Check your Owners Manual. In fact it's detremental to run low RPM. If you have been doing this since new, it's possible the rings and cylinder walls haven't seated which will lead to the exact issues you have ---aside from a potentially leaky injector. ....


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greg_g
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2008-12-31          158958


Quote:
Originally Posted by joepag08 | view 158954
I'll runs high rpms for an hour or so and see if that changes the rate. If so would that change the injector theory?Second, I'm going to send the oil off for analysis just to be sure. Will tell me amount of fuel dilution exactly and whether I'm wearing down metal too.
Since you bought the tractor from a landscaper, it's reasonable to assume the engine is well broken in by now. But as EW pointed out, running at normal (high) RPMs is a good thing. But it will do absolutely nothing to further troubleshooting. Injector leakdown occurs AFTER the engine has been shut off.

Knowing how fast the leakdown is occurring means nothing either. A leakdown is a problem that will never get better. So whether paying to figure out whether it's currently a "slow" leakdown or a "fast" leakdown is immaterial. Whereas it might be nice to know what ELSE is in your oil, it can't change the probability that the fuel contamination is from a dripping injector.

What you have to do is simply find the offending injector (or injectors) and replace them. Assuming this is not electronic injection, I just took a quick glance and found two Mitsubishi diesel injectors at $55 and $85 each. Not counting the bleeding time, removing/changing this kind of diesel injector not a whole lot more difficult than changing a spark plug.

//greg// ....


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kthompson
Join Date: Oct 2005
Posts: 5275 South Carolina
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2008-12-31          158959


Joe, one other question for you, do you use fresh fuel and do you use a good conditioner in it? Diesel acts different than gas from sitting. Again not a diesel mechanic but you might help your issue with some good hot working of engine and fresh fuel with proper fuel conditioner added. If you have a good tractor dealership ask for their recommendation on fuel conditioner to add but it is easy to find from Wal Mart to Tractor Supply and auto parts stores.

EW, note he bought the tractor used so he has not been running low RPMS since new, at most since he bought it.
....


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earthwrks
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2008-12-31          158961


Greg/Kenny: My bad; I should have read it.

But now that changes things, for the worst. Instead of NOT being broken-in, maybe it's just prematurely worn out. I for one am guilty of poor servicing for whatever reason--lack of mostly (taking) time. And I pay the price.

Crap happens outside of not taking time; my backhoe became "dusted" (sucked in dust and wore out the cylinders and rings) when I noticed the the intake hose from the air cleaner was off due to a broken clamp.

SO what I'm getting at is it's anyone's guess about the history of the machine. And being that it was not homeowner-owned chances are... ....


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Murf
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2008-12-31          158964


I still think it's an injector, even more so now in fact.

If it was stuck partly open, or has a bad tip, due to some carbon or something it would be pumping a lot of diesel fuel down that cylinder. If it happened in warm weather you might not even notice the problem.

If it was a bad seal or something like that IMHO it wouldn't have improved any.

I would ask the nearest big farm dealership who they use for injector service, I know there used to be a first class place in the London area, I can't recall the name, but it would be worth the few bucks to send out the injectors and get them serviced.

Just don't forget there are 'crush washers' under each injector, they must be replaced each time the injector is re-installed.

Best of luck. ....


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joepag08
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Posts: 11 Valley Lee, MD
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2008-12-31          158978


Good advice on the RPMs. And you're right, I don't really know for sure how it was cared for for the 1st 1000 hrs. I know there is an injector test in the manual. I should be able to remove them myself and find a tractor service shop that can test them. So most opinion is running towards injectors and not pump, huh? I was really dreading messing with the injection pump.

Happy New Year! ....


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