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Old 08-04-2018, 06:55 PM   #21
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Unless a valve is severely bent(unlikely from a piston strike) driving it is unlikely to cause problems.

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Old 08-04-2018, 07:20 PM   #22
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40 years of diesel experience leads me to think it has a bent valve if the runaway condition jacked up an injector it would be visibly damaged. Also in a runaway condition the engine could possibly turn 5to 6000 rpm causing all kinds stretching (valve interference or cylinder sealing) problems.So even if you determine it is a compression problem you still really won't know the cause. I would plan on a head removal project. Due to your travel constraints I would have a recon cylinder head nearby. Gene
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In the old days if a Detroit ran away you just walked away and had a coffee it stayed together you hauled if not well you cleaned up a mess.
Rack timing could be an issue to the last of the 6/71 on the farm is out of time right now and I dread having to do it
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Old 08-05-2018, 06:21 AM   #23
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Injector timing can make a lot of smoke if not set right. I have one (6-71)that needs an overhaul. Already have liner kits and plan to do it in the winter. However checking the injector timing I found one was off a good bit, resetting it really helped with smoke.
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Old 08-05-2018, 06:23 AM   #24
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By the way like your videos, you have a great little helper too
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Old 08-05-2018, 10:05 AM   #25
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Here is $.02 for the OP:

First and foremost, do not overthink and over-speculate this.

Secondly, get yourself the few special tools you need for working on your two stroke Detroit Diesel (DD). Injector timing gauge, wrenches to adjust valve lash and injector timing, and possibly the gauges to adjust the governor. That's the minimum. There is more mentioned below that it very useful and not too expensive.

Thirdly, pulling a head off a DD is as easy as it gets. There is no overhead camshafts and timing chain/gears to worry about. Just drain the fluids, remove a few fittings, disconnect the rack linkage, loosen the head bolts, and the head is off. To put the head back on you need the required gaskets, the correct 12 point socket for the head bolts, and a massive torque wrench. The installation of the head is easier if you get yourself a few extra cylinder head bolts, cut the heads off, generously chamfer the non-threaded ends, and cut a cross-slot in them. These bolts will be threaded into the block and serve as guides for the head installation. The cross-slots allows removal of the guide bolts after the head is secured with a few regular head bolts.

4) Once you are at the bus, remove the valve cover and make sure that you have plenty of lash on all valves. Remove the pin connecting the rack with the governor linkage, pull the rack into the off position and secure(!) it there. Verify that all injectors are fully off. Now perform a compression check by ear the way Christopher outlined. If you get a nice, even "re-ne-ne-ne-ne-ne-ne" skip to step 7.

5) If you hear that one or more cylinder's compression is week, remove all injectors and perform a leak test on all cylinders. The leak test will not only identify the weak cylinder(s) but also tell you whether the head or the piston/liner is the problem. You should prepare for the leak test by borrowing the needed hardware from someone or DIY it with an old injector, a couple of fittings, gauges etc. The size of the orifice between the gauges is not critical as we are looking for differences between cylinders and not for absolute values like during an annual airplane engine inspection. BTW, your local airport mechanic (A&P) would be a good candidate for borrowing the leak test gauge set if you can obtain or make the injector adapter.

When performing the leak test, make sure that the tested cylinder is exactly at TDC and keep your fingers away from anything that could move when you apply the test pressure. Remove ALL injectors before leak testing any cylinder unless you want to find out how an air start works.

(If the leak test is too much hassle for you, just pull the head and use your eyes, dye penetrant, etc. to find the compression leak.)

6) Pull the head and fix the problems you identified in step 5 and during further inspection.

If you can get to the connecting rod bolts in your installation, you can do an in-frame replacement of liners and pistons if necessary. For that I recommend preparing a few 1/4" flat steel bars that are as wide as the head is thick where the bolts are located and long enough to reach across the bores to the closest head bolts. These bars and a few head bolts will hold the liners in place that you do not want to move when you turn the crank to get to connecting rod bolts.

7) After re-installing the head (leave the governor linkage disconnected), adjust valve lash and injector timing as specified in the manual.

8 ) Perform the injector/rack synchronization as specified in the manual.

9) Reconnect the governor linkage and verify that the governor behaves as specified - especially the shut-off.

10) Check fluids, fire up, warm the engine up a little, recheck for leaks, and then put some load on the engine.

IMO, there are two idiosyncrasies that DD engines have. One, they do not like to idle for prolonged periods especially if they are older, dirtier, and more worn. The oil lubricating the cylinder walls will get from the intake ports into the air "box" and accumulate there. There are drains for this but in most cases they are clogged. With a clogged air box drain system, the accumulated oil will be blown into the combustion chambers once you rev up the engine, and will cause a temporary "run away".

Secondly, on a DD you have to perform the injector synchronization on the engine that otherwise your friendly diesel injection shop performs on a P-pump or similar system with the help of an expensive test stand. I see it as an advantage of a DD that you can (and have to) make sure that all injectors squirt the same amount at the right time with a few simple tools. This is not hard, especially not on a single head engine. It's just something you need to learn.

These engines are an ingeniously simple and reliable design. If it were not for the EPA Nazis and ever rising fuel cost, a DD would be hands-down the best engine for any DIY mechanic.
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Old 08-05-2018, 10:13 AM   #26
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Check the valve lash.
If a valve is bent it usually will open up the lash to a bigger size.
If a valve gets stretched the lash can drop to zero or less causing the valve to hang open and thus no compression just like a bent valve.
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Old 08-05-2018, 01:42 PM   #27
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Quote:
Originally Posted by Mekanic View Post
Check the valve lash.
If a valve is bent it usually will open up the lash to a bigger size.
If a valve gets stretched the lash can drop to zero or less causing the valve to hang open and thus no compression just like a bent valve.
Yes, I forgot to add this as another check before taking things apart.
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Old 08-05-2018, 05:26 PM   #28
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Further to what alpine44 says about the airbox drains, there are drain valves that are open at low idle to allow any accumulated oil to be blown out, and they should close at fast idle so full intake air pressure is maintained. On my engine one valve (I have one on each side) was stuck open because of sticky goo inside it, so I disassembled/cleaned/reassembled both of them. They need to point slightly downhill to work best, and instead of letting their slobber just drip down onto the ground I now run both their 3/8" tubes to a catch can (OK, a one-gallon plastic jug) so I can easily see exactly how much is coming out of each airbox.

You probably have even easier access to your injectors and head than I have, so it shouldn't be hard to do what alpine44 recommends, assuming you have the right tools. You can buy on eBay the Snap-On curved wrenches for adjusting valves and the injector height tool, and the Jake setting gauge if you have Jakes.

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Old 08-05-2018, 07:05 PM   #29
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Thank you all so much! I now have a plan in place for our next trip.

The oil in the airbox is exactly what happened to it, the mechanic said it was build up from being excessive idling when people were looking at it in the weeks before the auction. So it wasn't a complete runaway but was enough to cause the current problem. They shut it down with the key. It smoked like crazy when I picked it up and ended up like you see it in the video.
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Old 08-05-2018, 07:07 PM   #30
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After editing my video for today I realized the engine doesn't appear to be smoking as much. Take a look and tell me what you think. If you don't want to watch to whole video just skip ahead to about the 11:48 mark. Also, at the very beginning you can see how easy it starts before I swapped injectors, then later after the swap it was really hard to start each time I tried.




It seems like it's better. Could that old injector just not be opening or fused closed or something? Any other thoughts? Is it better or am I seeing things?

I should have retested each cylinder after I installed the new injector but I was discouraged because it was still smoking.
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Old 08-05-2018, 07:42 PM   #31
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Even after changing the injector that engine still sounds rough to me. How much power does it have when you drive it? It will drive on five cylinders, but not with any authority. When it's under load how much does it smoke, compared to at idle? Does the turbo spool up normally, or can you even hear it at all?

A few years ago a friend and I stripped some parts off a Crown like yours that was going to the crusher, seemingly because it smoked badly even though the company had tried all the usual tricks to fix it. The one thing they had not done was to check the injectors' timing, and if it's off by a tooth or two it will smoke. Maybe that's something you should also check?

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Old 08-05-2018, 07:56 PM   #32
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Quote:
Originally Posted by PB&G View Post
After editing my video for today I realized the engine doesn't appear to be smoking as much. Take a look and tell me what you think. If you don't want to watch to whole video just skip ahead to about the 11:48 mark. Also, at the very beginning you can see how easy it starts before I swapped injectors, then later after the swap it was really hard to start each time I tried.




It seems like it's better. Could that old injector just not be opening or fused closed or something? Any other thoughts? Is it better or am I seeing things?

I should have retested each cylinder after I installed the new injector but I was discouraged because it was still smoking.
You need to time the injector you just installed. While you are at it, check valve lash and injector timing on all cylinders. Chances are that the engine will run fine after that. As someone else pointed out before, a short runaway is not a big deal if the engine does not grenade. Even if the valves float so badly that the piston gets them, they go straight into the combustion chamber as far as I remember and I do not see how just the valve(s) in one cylinder could get bent.

Look up in the manual what timing gauge you need and get the gauge and the bend wrenches on ebay.
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Old 08-05-2018, 08:01 PM   #33
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I would set the injector timing next. I am referring to using the timing gauge/pin. You will need the airbox cover off for that cylinder to set the timing, so might as well scope the cylinder.

The smoke is better for sure.
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Old 08-06-2018, 12:23 AM   #34
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Quote:
Originally Posted by Iceni John View Post
Even after changing the injector that engine still sounds rough to me. How much power does it have when you drive it? It will drive on five cylinders, but not with any authority. When it's under load how much does it smoke, compared to at idle? Does the turbo spool up normally, or can you even hear it at all?

A few years ago a friend and I stripped some parts off a Crown like yours that was going to the crusher, seemingly because it smoked badly even though the company had tried all the usual tricks to fix it. The one thing they had not done was to check the injectors' timing, and if it's off by a tooth or two it will smoke. Maybe that's something you should also check?

John
The power seems good but I don't know what normal should feel like. It smokes a bit but not as much as when I picked it up. It is probably 75% better after I drove it to the storage place and apparently even better after the injector swap. The turbo sounds like its spooling up okay, I can hear it when I accelerate.

I will absolutely be checking the injector timing first on my next visit.

Quote:
Originally Posted by alpine44 View Post
You need to time the injector you just installed. While you are at it, check valve lash and injector timing on all cylinders. Chances are that the engine will run fine after that. As someone else pointed out before, a short runaway is not a big deal if the engine does not grenade. Even if the valves float so badly that the piston gets them, they go straight into the combustion chamber as far as I remember and I do not see how just the valve(s) in one cylinder could get bent.

Look up in the manual what timing gauge you need and get the gauge and the bend wrenches on ebay.
This is my plan for the next trip. My manual says I need 1.470 timing. I'll be on Ebay tonight!

Quote:
Originally Posted by Ronnie View Post
I would set the injector timing next. I am referring to using the timing gauge/pin. You will need the airbox cover off for that cylinder to set the timing, so might as well scope the cylinder.

The smoke is better for sure.
I thought it was better but wanted to make sure it wasn't wishful thinking.

Thank you all so much for all of the insight. It also helps when all of you are pretty much saying the same thing!

Now I'm excited to get back out there

Looking at my manual and although there a isn't good picture, it sure looks like there are supposed to be holes in the injector tip. I could not see any holes in the one I removed. The tip looked like one solid piece. I didn't think to compare them before installing the new one other than the number.
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Old 08-06-2018, 05:44 AM   #35
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The holes are tiny but should be visible to the naked eye.

I had to work on the injectors for an old(1943) Cummins HBI engine. Cleaning the tips was with a .006" drill in a pin vise, had to use reading glasses and one of those magnafing lamps. 6 holes per injector, 12 injector for 2 engines. Did them all without breaking the drill bit. Funny thing is the drill bits came in a little plastic tube, and neither me or my wife could see them in the tube, thought for sure it was an empty tube. Well with some magnafication we did see them. Yikes. not used to working so small.
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Old 10-29-2018, 10:48 PM   #36
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I finally have an update! We're back in Fresno and I had a chance today to pull the rocker cover again. I had to drive the bus a very short distance to a place I can work on it since I'm not supposed to do any mechanic work at the storage lot. The bus had no power and would rev very slowly. It was a chore just to get over the crown in the road when crossing a street from a dead stop.



So after I pulled the cover I noticed one of the rocker bridges was crooked and not on the valves on the 3rd cylinder. I must have bolted them back on and somehow misaligned one when I changed the injector. I put everything back together, correctly this time, then checked the lash on number 3. The two valves on the blower side are opened up quite a bit. The rest appear okay on a quick check.



That had me thinking that those two valves could be bent. But the strangest thing happened. It still smokes like before but now it sounds a lot smoother and revs with no problem. The best part is that it now has ugh more power and no problem at all going uphill from a stop or otherwise.


We have 3 days left and we're trying to get the interior to a point that we can get rv insurance so that's our priority at the moment. With that said, next I will use my little camera to check the inside of the cylinder and the valves on 3. Then I will set the lash on all the valves and finally time that new injector as it is not set right when checking it with the pin. The others are okay on injector timing.


I think I might be on to something! I'll have another update in a few days with pics and video


Edit: I also cannot see any holes I'm the tip of the old injector.
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Old 10-30-2018, 06:37 AM   #37
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Good news for sure.
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Old 11-01-2018, 12:23 AM   #38
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Okay, today I pulled the air box cover on #3 and put my little camera in there. The valves do not appear bent to me. There was also no evidence of any of the valves contacting the piston. It looked normal to me.


The injector timing on the new injector was way off so I corrected that. The rest were okay.


The lash on #3 and #6 was opened quit a bit. My .020 feeler fit right in so it was probably more than that. I set those to .016 as best I could. It's tricky to get them to stay when tightening the jam nut.


After all of that. It still smokes about the same.



Tomorrow I will check the compression. Stay tuned.


Any other suggestions would be appreciated and encouraged.
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Old 11-01-2018, 05:22 AM   #39
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A few thoughts,after checking compression.

1.At this point it might need to be driven enough to clear out any fuel, or oil residew. This could well be in the exhaust system.
2. The other injectors may not be in much better shape then the first one. It would be good to have them tested and cleaned/repaired as needed
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Old 11-01-2018, 10:01 AM   #40
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Quote:
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A few thoughts,after checking compression.

1.At this point it might need to be driven enough to clear out any fuel, or oil residew. This could well be in the exhaust system.
2. The other injectors may not be in much better shape then the first one. It would be good to have them tested and cleaned/repaired as needed

Thanks. Hopefully the compression checks out okay
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