L295DT Timing Slipped - why?

[fj40dave]

I'm taking apart the diesel motor in this L295DT - thinking the bottom end is needing some attention, and I find the gears out-of-time (marks not lining up).

Any ideas on how this happens, and what might be wrong?

Dave

 

[Ob1kubota]

fjdave are you absolutely sure your at TDC on the firing stroke? Did you put a dial indicator on number one piston to check lift? Tell us more about your tear down this is going to be a good post!

 

[eserv]

Hi fj40dave.
Your timing hasn't slipped. The middle gear on that engine is simply an idler gear and as such is not a 2 to one ratio with the other gears. if you turn the engine over enough times it will probably all line up again or you can simply put the cam, injection pump and crankshaft so the marks on them are centered as well as possible on the center gear. then you can remove the center gear and put it on so the marks line up being careful to not move any of the other gears. if you count the teeth on the gears you will find the Cam and pump gears have twice as many teeth each than the crank gear. The center gear has some other number ( not sure if its more or less than 2 times but it certainly isn't two times!
Hope I explained this well enough!
Ed

 

[eserv]

Hi
As an interesting aside to this problem I did have the timing slip in a kubota M9000 once! The tractor came in, very hard to start, smoking bad and wouldn't rev past 1500 rpm. I did a compression test, all good, Checked injection timing alright as well. removed the front cover and the timing marks were like yours, AHA! found the problem! removed the idler and found it's bushing loose and the pin it rides on worn so we replaced them and put it all back together and it ran the same way!!!!
I took the valve cover off and put the engine on tdc firing # 1 using # 4 overlap as reference and the injection pump was 180 degrees off! How could this be?
What had happened was that the camshaft had siezed in it's bore and sheared the cam gear key, it turned almost exactly I/2 turn then broke free in the block and cam started turning again but the cam is now 180 degrees out making the injection point at the end of exhaust beginning of intake. It still had fuel and compression so it would run very poorly! This tractor was still on warranty so Kubota supplied a new block and camshaft but as you can probably guess I didn't make flat rate on that job!!
Ed Service

 

[fj40dave]

Ed, thank you for the information!!! That's awesome, man!

Looks like I'm still trying to detect why there's a problem with this motor then.

I'll be looking at that cam (and pin) closely when I get to taking it apart. I'm going to turn the crank until the marks line-up, then dig into the head removal next.

However......today is sunny and brisk....means I gotta get out on the bike.

Dave

 

[Ob1kubota]

Wow Ed what a story! Never knew the older indirect injection 4 cylinders had a habit of seizing up camshafts. I bet you Kubota grapped that block up quick. Did the District Service Manager ever tell you what they found on tear down? Interesting.... I lost a M11 Cummins like that years ago when I was with Komatsu but the Tech had misaligned the cam bearings oiler holes ( how the 'H' do you do that ) but he did and it cost me another warranty long block.

 

[eserv]

Hi Ob1kubota.
I don't believe they had a problem with siezed camshafts, I really think it was an isolated case. They didn't even ask for the block back! The service rep just looked at it in the shop and took a few pictures. These Kubota engines don't have cam bushings (many Kubota's don't) the cam just runs in the cast bore in the block. When I took it apart I could see clearly where the cam had grabbed in the bore and picked the cast iron. I think maybe the failed bushing in the idler gear robbed the cam journal lubrication but Kubota never gave me an answer. They paid the warranty claim though even the little extra I'd put in for diagnosis! It didn't cover ALL the time I put into it but I guess the education was worth something too
Ed

 

[fj40dave]

I got the head pulled today - after setting the motor to TDC by turning it over several times (THNAK YOU ED!)
Pic's of the valves/piston/cyl attached.
Visually, they look pretty good.

I never mentioned what was wrong - why the tear-down:

This motor was very difficult to start, and then there would be horrendous ammounts of blue and white wmoke. It made a really bad lower end kind of growl as well. No power.
The owner had changed oil once and then noticed that it was "overfull" shortly therafter: My thought was a stuck injector allowing diesel fuel into the oil....dilluting it and probably causing premature wear of the bearings.

Well.....I've not found anything obvious yet.

Going to pull the lower half/pan and check rod's and bearings next....and that cam - for the shear pin thing mentioned above.

 

[aquaforce]

Were you able to determine what was filling up? If the fluid level gained then something should be low or noticeable, such as milky from water/antifreeze or a reservoir low such as hyd/trans.

If I see the pic right #3 kind of gets my interest up. Unless it is just oil smears from work it looks like to much oil in the cyl.

 

[eserv]

Hi fj40dave,
I don't believe there is much chance of your problem being the camshaft key. It is not a shearpin as such and is not designed to ever slip! I still don't understand why the valves didn't foul the pistons in the engine I worked on, if they would have it would have helped immensely in the diagnosis!
But, to check your cam, if you put the engine at top dead center opposite firing stroke, the valves should be on "overlap" that is, the exhaust should be just closing and the intake just starting to open. overlap is quite small in your engine (most diesels for that matter) so if it is at all out it should be evident. both valves should be very slightly open the same amount.
Ed Service

 

[fj40dave]

The head and block (pistons) look good - the oil is just thumb smears from moving 'em around.
I have the bollom pan pulled, and the rod ends feel/look good as well. There's a little fore/aft play in each, but until I check the allowance, I imagine they are within allowance. There wasn't any shavings or "chunks" in the pan.
The oil looks - well - like oil, not milky or contaminated, unless there's hydraulic oil in there with it, and I can't readily tell that.

I took the hydraulic pump apart and will be changing the seals.....nothing obvious there either, but who knows when it's under pressure.

 

[fj40dave]

Hi fj40dave,
I don't believe there is much chance of your problem being the camshaft key. It is not a shearpin as such and is not designed to ever slip! I still don't understand why the valves didn't foul the pistons in the engine I worked on, if they would have it would have helped immensely in the diagnosis!
But, to check your cam, if you put the engine at top dead center opposite firing stroke, the valves should be on "overlap" that is, the exhaust should be just closing and the intake just starting to open. overlap is quite small in your engine (most diesels for that matter) so if it is at all out it should be evident. both valves should be very slightly open the same amount.
Ed Service

Dang....I already have the head off....can't check the cam/overlap.

 

[eserv]

Just put your pushrods in on number one and roll the engine over with your finger on top of both when they feel equal you should be on tdc
Ed

 

[fj40dave]

The front piston is at the top of it's travel, and the timing marks have lined up - this would be TDC - yes?

I don't have the head back on - have to order gaskets and seal stuff next.

Is the cam difficult to pull.....I could check it at this poing I think.

 

[eserv]

You don't need the head on, Just put the pushrods in and hold them down with your fingers, turn the engine until you feel the one pushrod go down and the othe one just start to go up. This is valve overlap and it should corrispond to the piston on that cylinder being it the top. The camshaft is easy enough pull out. you will need to remover the cam followers ( lifters) and there is two bolts behind the cam gear accessible through holes in the cam gear remove them and the cam will pull out. Be absolutely sure you put the followers back into the same holes you take them out of when you reassemble! If you don't there is a high probability of the cam being damaged! It sure can't hurt to check the cam for wear on the journals and lobes when you have the head and front cover off. ( it'll never be easier! )
Ed

 

[fj40dave]

Got the cam out, and the lifters kept in order so they can go back in where they came from.

Mic'd the cam lobes:
1 = 33.325
2 = 33.452
3 = 33.337
4 = 33.362
5 = 33.401
6 = 33.375

My service manual doesn't have the spec's for the cam lobe wear - but they all are pretty close together, and the cam and lifters look fine, no scoring or gouges or heated up areas.

 

[fj40dave]

I converted all the inch measurements figuring they would be given in metric....but here's what I had in inch:

1 = 1.312
2 = 1.317
3 = 1.3125
4 = 1.3135
5 = 1.315
6 = 1.314

All within allowable use specs...cool!

I'm beginning to think this was just a hydraulic pump seal problem......and maybe a little something going on with that rear cylinder head gasket in a minor way (looking at it more closely).

Thank You Vic for the data

Dave

 

[fj40dave]

Well....ordered >$500 in parts from Messicks today.

Hopefully begin rebuilding next week.

Couple questions:

Flywheel resurface spec's.....I'm taking it off and down to the machine shop, but I suspect they won't have the details to know what the limits are.....nice if I could tell 'em. I don't think this flywheel has been off before, so it shouldn't be a problem.

The fuel injection cam:

Specs for when I mic it out?

I'm thinking the hydraulic pump seals were the culprit.
The rest of the motor is looking very good - not going (don't want to disturb something that probably isn't worn) to pull the pistons and look at the crank....feels tight and no grinding or "bad feeling stuff"....no shavings or glitter in the oil either (nothing in the bottom of the pan).

 

[RDR]

After getting this far I would at least pull the rod caps and check the bearings. You don't have to pull the pistons. I don't like the color of the block surface and head surface. Also #1 cylinder doesn't look like it was firing correctly. How much blowby did this engine have? Did the oil smell like diesel or hydraulic oil.

When I bought my M5400 it was full of hydraulic oil to the top of the dipstick hole. It fired right up at the auction. It sounded so good I bought it with out having looked at the tractor at all. Lesson learned.

 

[fj40dave]

spose your right.....I think I will pull the rod caps.

The oil did fill up and pour out the dip stick hole, but I didn't know it could be hydraulic oil when I checked - it just didn't smell like diesel fuel which is what my first thoughts were.

I'm thinking of just cleaning the head surface and block surface and (of course) new gasket. I'll make sure it's not warped (straight edge the head).