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D311 Engine-Need some guidance.

D311 Engine-Need some guidance.

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AGES CAT
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I have a D311 in a 212 Motor grader. The engine has had new sleeves, valves ground, converted to electric start, and the list goes on. The engine starts very well. Initially, the engine fired on #1, #2 and #3 cylinders, but #4 was cold.(fingers on the exhaust manifold). We moved the #4 pump to the #1 position to determine if the pump was the problem, and the #1 went cold and the #4 fired correctly. This would indicate that the pump was bad. A replacement pump has not corrected the problem. #3 initially was running a little cooler but has warmed up so it is working. When the engine is under load, with the blade in the dirt, the engine appears to be firing on all four.

Pumps have been changed several times (CAT new old stock) and a perfectly running D2 as repalcemnts. Plunger lift @ 1.736 is correct, fuel pressure in the green(new gears, plate and shaft, new bypass spring and seat.). Filters are new and the fuel filter chamber is clean. We seem to be getting good flow to the pump manifold. We are going to check the gauge to assure that the fuel pressure is correct. There is about 6" of fuel in the tank. but it has been half full with no change. (We are bleeding at the pump and at the injector to eliminate the air.)

We are at a loss as to what it might be. We thought maybe there was restricted flow to the fuel manifold which supplies fuel to all four pumps, but when the machine is working it runs on all four. We have checked the engine cylinder compression, 250#+.

Any help would be greatly appreciated. Both I and the guy working on it with me have been lifelong mechanics, and owned numerous CAT machines. What are we missing?
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Sun, Sep 29, 2013 9:41 PM
Old 3T lover
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Wild guess, point of injection, timing off a little and that's the weakest pump.
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Sun, Sep 29, 2013 9:47 PM
Old Magnet
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Reply to Old 3T lover:
Wild guess, point of injection, timing off a little and that's the weakest pump.
At 250# compression pressure is to low in that cylinder. Not enough to make auto-ignition temperature.

Although Cat didn't rely on compression pressures for diagnostics (they do now) here is some expected compression pressures as furnished by edb:

If all cylinders have a similar reading and considering all the work that has been done I would suspect there is a problem with camshaft timing.
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Sun, Sep 29, 2013 11:41 PM
ccjersey
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I'm guessing the 250 psi compression test result is as high as you could read with the tester you had????? Serously doubt the rest of the cylinders would fire if they were anywhere close to 250.

I think you will gain more from a proper compression test and then if it shows a low cylinder, a leak down or really just a leak test with compressed air into the cylinder with piston at TDC of compression stroke will tell you more about where the leak is.

If all cylinders have approximately equal, but low pressure, then maybe camshaft timing, but just seems unlikely for that to cause a single cylinder to drop out preferentially. Something like amount of valve seat and valve grind, piston surface/type would have to be different about that one.

OH.................could be something in the intake blocking air flow, though I would think of that causing a misfire at full speed instead of preferentially at low idle. Have found some strange stuff in engines before. Worst was a large chunk of rag in the intake runner of a D333. It went alll the way to the far end of the head from the air filter pipe. I'm guessing those guys never figured out why the old dozer sounded like that!

You don't mention injectors..........have you swapped any between cylinders or replaced them?

How recent was the rebuild? Has it run long? Problem show up on first startup or has the tractor run well since the rebuild.

It would be pretty easy to take off the valve cover and check camshaft timing as the valves "rock over" at TDC of exhaust. Also could measure lift to check camshaft wear. That is another possibility as far as the injection pump camshaft goes. You could have the lifter set correctly, but there still be enough wear on the lobe that the pump wasn't getting a full stroke.

One last idea, it really doesn't sound like your description, but are you sure the pumps are correctly timed to the rack when they were installed. I've heard a D320 start up with the pumps out of time on the rack, and it was really rough.
D2-5J's, D6-9U's, D318 and D333 power units, 12E-99E grader, 922B & 944A wheel loaders, D330C generator set, DW20 water tanker and a bunch of Jersey cows to take care of in my spare time😄
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Mon, Sep 30, 2013 1:14 AM
Sasquatch
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Reply to ccjersey:
I'm guessing the 250 psi compression test result is as high as you could read with the tester you had????? Serously doubt the rest of the cylinders would fire if they were anywhere close to 250.

I think you will gain more from a proper compression test and then if it shows a low cylinder, a leak down or really just a leak test with compressed air into the cylinder with piston at TDC of compression stroke will tell you more about where the leak is.

If all cylinders have approximately equal, but low pressure, then maybe camshaft timing, but just seems unlikely for that to cause a single cylinder to drop out preferentially. Something like amount of valve seat and valve grind, piston surface/type would have to be different about that one.

OH.................could be something in the intake blocking air flow, though I would think of that causing a misfire at full speed instead of preferentially at low idle. Have found some strange stuff in engines before. Worst was a large chunk of rag in the intake runner of a D333. It went alll the way to the far end of the head from the air filter pipe. I'm guessing those guys never figured out why the old dozer sounded like that!

You don't mention injectors..........have you swapped any between cylinders or replaced them?

How recent was the rebuild? Has it run long? Problem show up on first startup or has the tractor run well since the rebuild.

It would be pretty easy to take off the valve cover and check camshaft timing as the valves "rock over" at TDC of exhaust. Also could measure lift to check camshaft wear. That is another possibility as far as the injection pump camshaft goes. You could have the lifter set correctly, but there still be enough wear on the lobe that the pump wasn't getting a full stroke.

One last idea, it really doesn't sound like your description, but are you sure the pumps are correctly timed to the rack when they were installed. I've heard a D320 start up with the pumps out of time on the rack, and it was really rough.
I was going to hit on what ccjersey put towards the end of his post above, which would've been pump plunger to rack timing. But the other thing I was thinking (and this is way out there, but I suppose it could be possible) is that since the geared segments on the pump plungers are only clamped to the plunger rods, they could've been "twisted" out of their proper position if they were siezed in the pump bores at one time and the fuel rack was forced through a certain degree of its fore-and-aft travel by some sort of leverage application (prybar, screwdriver, etc.). But for this theory to work out, it would mean that three plunger segments would've had to twist out of position a bit and become slightly "advanced" and one stayed where it should be. So instead of having one weak cylinder and three normal, you would actually have three too strong and one normal. Also, I didn't read in the original post if all four pumps and plungers had been changed out at the same time, which would totally take all of this right out of the equation.

Anyway, it's just something I thought of when pondering how the engine would appear to be running normally under load but not at idle, and how possible governor operation might be opening all the pumps up just enough for the one alleged lower volume plunger to open enough to actually start contributing power. It could also explain why other known good pumps haven't changed the condition, assuming that you've only done the change-out on the weak firing cylinder. But again, if you've already swapped all four at the same time and still have the same condition, then disregard all this.

Edit: One last thing, are you sure you have the correct pump and plunger assemblies on the three strong firing cylinders? It could be possible that they've been replaced at one time with pumps from a D315 or other bigger bore engine, which may affect fuel output/volume? Just thinking some more, I'd really like to know what you find if you get it sorted out.:noidea:
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Mon, Sep 30, 2013 7:59 AM
edb
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Reply to Sasquatch:
I was going to hit on what ccjersey put towards the end of his post above, which would've been pump plunger to rack timing. But the other thing I was thinking (and this is way out there, but I suppose it could be possible) is that since the geared segments on the pump plungers are only clamped to the plunger rods, they could've been "twisted" out of their proper position if they were siezed in the pump bores at one time and the fuel rack was forced through a certain degree of its fore-and-aft travel by some sort of leverage application (prybar, screwdriver, etc.). But for this theory to work out, it would mean that three plunger segments would've had to twist out of position a bit and become slightly "advanced" and one stayed where it should be. So instead of having one weak cylinder and three normal, you would actually have three too strong and one normal. Also, I didn't read in the original post if all four pumps and plungers had been changed out at the same time, which would totally take all of this right out of the equation.

Anyway, it's just something I thought of when pondering how the engine would appear to be running normally under load but not at idle, and how possible governor operation might be opening all the pumps up just enough for the one alleged lower volume plunger to open enough to actually start contributing power. It could also explain why other known good pumps haven't changed the condition, assuming that you've only done the change-out on the weak firing cylinder. But again, if you've already swapped all four at the same time and still have the same condition, then disregard all this.

Edit: One last thing, are you sure you have the correct pump and plunger assemblies on the three strong firing cylinders? It could be possible that they've been replaced at one time with pumps from a D315 or other bigger bore engine, which may affect fuel output/volume? Just thinking some more, I'd really like to know what you find if you get it sorted out.:noidea:
Hi AC,
all good suggestions to check given above.
Given that your changing its' positition dead cylinder problems are not being improved by injection pump change outs and seem to be confusing in their symptoms, I have encountered erratic running due to injectors leaking combustion gasses back into the fuel gallery.
Suggest also getting injectors tested and/or exchanged with known good ones as a test.
Cheers,
Eddie B.
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Mon, Sep 30, 2013 11:36 AM
snowshoveler
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Reply to edb:
Hi AC,
all good suggestions to check given above.
Given that your changing its' positition dead cylinder problems are not being improved by injection pump change outs and seem to be confusing in their symptoms, I have encountered erratic running due to injectors leaking combustion gasses back into the fuel gallery.
Suggest also getting injectors tested and/or exchanged with known good ones as a test.
Cheers,
Eddie B.
Not that I know anything...
But could it be possible that your valve clearance is a little snug on the #4 cylinder.
Regards Chris
193? d4400 cat powerunit
1950 john deere M
1959 international t5 crawler
1977 powerking 1216 tractor
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Mon, Sep 30, 2013 10:17 PM
Old Magnet
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Reply to snowshoveler:
Not that I know anything...
But could it be possible that your valve clearance is a little snug on the #4 cylinder.
Regards Chris
One I forgot....a case of weak valve springs and/or improper valve spring installed height. Easy to check, drive a big screwdriver into the coils while running and see if that cures the local problem.
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Mon, Sep 30, 2013 10:25 PM
AGES CAT
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Reply to Old Magnet:
One I forgot....a case of weak valve springs and/or improper valve spring installed height. Easy to check, drive a big screwdriver into the coils while running and see if that cures the local problem.
Thank you all for yor responses. When we moved the pump that was supplying fuel to #4 (missing) to #1 and moved #1 to the #4 position, and the missing moved to number #1, we thought we had it, because the problem followed the pump. This last Saturday we replaced the pump with a CAT OEM pump and nothing changed. We then used a pump taken from another D2 sitting next to the grader and nothing changed even with a known good pump. When you drop the blade or drive it up hill, the governor action will allow it to run on all four cylinders.

We have moved lines, nozzles, etc. to further isolate the problem, but nothing that we did last Saturday made a difference, thus the note for some better ideas.
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Tue, Oct 1, 2013 12:41 AM
daron
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Reply to AGES CAT:
Thank you all for yor responses. When we moved the pump that was supplying fuel to #4 (missing) to #1 and moved #1 to the #4 position, and the missing moved to number #1, we thought we had it, because the problem followed the pump. This last Saturday we replaced the pump with a CAT OEM pump and nothing changed. We then used a pump taken from another D2 sitting next to the grader and nothing changed even with a known good pump. When you drop the blade or drive it up hill, the governor action will allow it to run on all four cylinders.

We have moved lines, nozzles, etc. to further isolate the problem, but nothing that we did last Saturday made a difference, thus the note for some better ideas.
Carbon buildup in prechamber?

Daron
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Tue, Oct 1, 2013 2:14 AM
Old 3T lover
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Reply to AGES CAT:
Thank you all for yor responses. When we moved the pump that was supplying fuel to #4 (missing) to #1 and moved #1 to the #4 position, and the missing moved to number #1, we thought we had it, because the problem followed the pump. This last Saturday we replaced the pump with a CAT OEM pump and nothing changed. We then used a pump taken from another D2 sitting next to the grader and nothing changed even with a known good pump. When you drop the blade or drive it up hill, the governor action will allow it to run on all four cylinders.

We have moved lines, nozzles, etc. to further isolate the problem, but nothing that we did last Saturday made a difference, thus the note for some better ideas.
[quote="AGES CAT"]Thank you all for yor responses. When we moved the pump that was supplying fuel to #4 (missing) to #1 and moved #1 to the #4 position, and the missing moved to number #1, we thought we had it, because the problem followed the pump. This last Saturday we replaced the pump with a CAT OEM pump and nothing changed. We then used a pump taken from another D2 sitting next to the grader and nothing changed even with a known good pump. When you drop the blade or drive it up hill, the governor action will allow it to run on all four cylinders.

We have moved lines, nozzles, etc. to further isolate the problem, but nothing that we did last Saturday made a difference, thus the note for some better ideas.[/quote]

Had Cat engines that ran ragged as heck....skip, pop, sputter but would straighten up, run good and push good under a load and right back to running ragged with no load. Loped and sounded like a hot rod engine with a full race cam.....I don't have the books and I don't remember the proper words/terms but your point of injection is off.....need to pull your pumps, depth mic the injector pump cam and set the timing. Sounds like the timing is off a degree or two from collective wear in the engine gear train..
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Tue, Oct 1, 2013 3:43 AM
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