Injectors Help

[rlopatterson]

We are diagnosing rough running issues. Fired the mechanic as he blamed compression as issue and engine needed to be rebuilt. We rechecked the compression on the engine and perfect 450 psi on each cylinder.

So, that takes to fuel. Pulled the injectors and there is a lot of carbon and does not look like they are seating well. See pictures. Anyone with experience think this may be the problem, or should we go ahead and pull the IP and send that out as well?

Sending out the injectors and replacing the copper washer on the bottom.

What would be the best way to clean this carbon without dropping it in the cylinder?

The injectors look like they were redone in the past few years by the prior owner because they did not have any paint on them, but going to send out anyway. We did break the leak off pipe - darn it.

[Fiveslide]

A Shop vac with a smaller diameter hose taped to the suction hose. Perhaps a small wire brush to help break up the build-up on the injector seat.


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[rlopatterson]

Main question. Would the injectors not sealing properly as seen in the pictures, cause a bad running issue?

[Outwest34au]

Yes, the vac and hose trick. Paper towel and a small gun/ bottle cleaning brush or even steel wool.
I would be using the thinnest smear of grease on the new copper washers also.

[jimbunyard]

It could, next time before you take the injectors out, with the engine running, put a little diesel or oil on the joint where the injector screws into the block. If they're leaking at the seal they will blow bubbles.

Also, define 'rough running issues'. Make sure the injectors you have are the correct ones for your engine (by serial number). Also make sure fuel is clean, filters are clean and well seated and that the fuel system has no leaks, especially on the supply side, introducing air into the system, and that the intake and exhaust paths are clear.

The injection pump would be the last thing I would suspect though, not knowing any history of the problem.

[rlopatterson]

Issue: Engine hunts at idle under 1K RPM. Runs as if there is a miss. At idle when running goes from hunt to smooth idle. Idle is set at 850 RPM and tested with scope to match tach. Diesel knock at higher RPM's and smooths out over 16K, but will top at 2400 where should be 3000K. Valves adjusted, one mechanic tested compression and said one was low and the issue. We retested and all are at original spec of 440 psi.

Injectors appear as they were done by prior owner as clean and not painted. Pretty clear there was no seal on the injectors with the carbon leaking up to the thread.

[Ecos]

Remember, the injector only worked correctly when they tested it. It's my understanding that they don't often overhaul them, they clean and test them. It's possible they're leaking or spraying poorly despite the lack of paint from being cleaned and tested in the past.

[C-Gazer]

Were you running the prop when you could not get full engine revs?
I have had this happen when my prop was heavily fouled. When you reinstall the injectors and they have been bled and the engine is running a simple check of the fuel pump is to crack open each injector one at a time . The revs should drop the same amount on each cylinder if the pump is OK. Cracking open the injector(1/4 turn) simply means loosening the injector line nut on top of injector. Be careful the fuel to the injector is under very high pressure.
Good luck!

[forsailbyowner]

If you go the IP pump route check out dieselitems.com they told me most pumps cost $375 to rebuild and they include free injector service with pump rebuild.

I recently had mine out. I plugged up the hole in the bottom ( I think I used the eraser end of a pencil) and blew out the seat and cavity they sit in with compressed air.

Were all the compression tests done cold? My old diesel misses on one cylinder till it warms up. I guess as things expand and compression rises in that cylinder.

[a64pilot]

Originally Posted by forsailbyowner

My old diesel misses on one cylinder till it warms up. I guess as things expand and compression rises in that cylinder.

Most probably a sticking valve, then as the engine warms up the valve no longer sticks, can cause problems with bending a push rod etc.
Google "engine morning sickness" for some explanations.

[jimbunyard]

I realize the injectors don't screw into the block, brain fart.

Agree with you that the injectors were manipulated by previous owner, which is why I suggested making sure that they are correct by s/n. Just because they screw in doesn't mean that they are, there are pressure and fuel volume considerations.

After looking at the pictures again, it certainly does look like the one on the right
was sealing less well than the one on the left. Would that cause the symptoms described? Maybe. By all means clean the seats well when reinstalling the injectors, and use the parts and procedures for the specific model and s/n engine you have per the manufacturer. (Had a Volvo once that the pump shop said seal injectors one way the Volvo manual said another way, turns out there was a change made by Volvo that wasn't efficiently communicated. I went with what the pump shop said and had no problems, found out later about the Volvo change.) Keep it clean as possible, but don't worry too much about a little carbon falling into the chamber.

That the engine sometimes runs smoothly and at other times doesn't (as well as the good compression numbers) indicates that there is probably no problem with the rings, valves or head sealing. Likewise with the injection pump and governing mechanism.

So we go to fuel supply. Again make sure the filters are seated well and there are no intake side leaks that would allow air to be drawn into the system. The fuel tank pickup could be clogged (I had a similar lack of high end rpm issues once, some moron had put a strainer on the end of the pickup tube in the fuel tank. Cut it off, problem disappeared.) Also make sure the vent line for the tank is not obstructed, very important. Check the lift pump too, an inline fuel bulb pump can sometimes be used to identify a faulty lift pump; when the engine starts missing does pumping the bulb eliminate the miss? Maybe not so much with a tank vent or pickup issue though.

What make engine and how many hours?

[rlopatterson]

Injection shop said it is a clear issue that the only thing sealing from the pictures were the threads. PO replaced the sealing washers with the wrong type, size and material or did not replace at all. Or they did not properly clean the carbon before reinstalling the injectors, so they would not seat properly.

The picture on the left at least shows the seal line with leakage in once spot. The one on the right the gasket was not making any contact with the head.

They recommend for a proper seat to remove the head and a special tool that cleans the seat thoroughly, then they can be 100% sure.

They suspect a combination of injectors and the timing may be slightly off on the CAV Pump. Taking up to be tested and will post the findings.

[Fiveslide]

They recommend for a proper seat to remove the head and a special tool that cleans the seat thoroughly, then they can be 100% sure.

There are thousands of "special" tools out there, some are worth their weight in gold, others are so tremendously worthless. Some can be made from common household materials. What kind of tool are they going to use and is it worth pulling the head off, or can it be done by the methods previously mentioned here?

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[rlopatterson]

It was the injector seats. Injectors tested perfect, cleaned them up and put back on the engine with new copper washers and cleaned the carbon with seafoam spray, shop towels, etc. Tightened them better this time and started the engine right up to a very smooth idle and run.

[jimbunyard]

Good for you. Just out of curiosity, did you pull the head and injection pump?