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Old 02-06-2021, 04:37   #1
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Smoking Perkins 4-108

I recently replaced the fuel pump and the injector pump on a friends older Perkins 4-108. He experienced a traumatic diesel runaway as he was entering a large marina solo. Fortunately he was able to put the boat into a tight circle and go below to remove the companionway steps and cabinetry to snuff out the engine with a throw pillow before any collision occurred.
The first thing I did was to check the oil level, and it was filled to the top of the dipstick. So, I replaced the primary fuel diaphragm lift pump. When we started the engine, it ran OK for about 10 minutes and then blew a head gasket; emitting loud compression noises and smoke into the cabin. I immediately snuffed out the engine again, no runaway yet, and checked the oil level. It was way over the full mark again. Obviously so full that the cylinders ingested the non-compressible fuel/oil mix. So...I pulled the head, after much difficulty with the head bolt/studs corroded into the head, and ordered a rebuilt fuel injector pump from North Atlantic Diesel. The head and injectors were sent out to a shop for service and were installed with new gaskets and the rebuilt injector pump.
After reinstalling the serviced and rebuilt parts the engine started right up after bleeding the injectors and ran fine.
The problem is that it smokes quite a bit. My question is, could the high rpm runaway conditions have glazed the cylinders, causing this problem? And if so does anyone have any ideas to fix the problem, other than a complete teardown rebuild. The engine has very little time on it, slip time only, as there have been other issues with the boat. So, it has had no hard hours put on it at maximum load.
thanks in advance,
Bill in JB
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Old 02-06-2021, 05:59   #2
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Re: Smoking Perkins 4-108

Let me recommend that you check compression on the engine, which will answer the scored/glazed cylinder issue. If that's OK, move on the whether the injection system is too rich. The black smoke is incompletely burned fuel. That means that there is more of it than the cylinders are burning. That in turn likely means that either the compression is too low to burn all that stuff on each stroke or there was too much of it there to begin with.
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Old 02-06-2021, 06:49   #3
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Re: Smoking Perkins 4-108

could the fuel pump timing be off a smidge causing the fuel to be injected too late resulting in an incomplete burn?
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Old 02-06-2021, 09:06   #4
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Re: Smoking Perkins 4-108

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Originally Posted by marcjsmith View Post
could the fuel pump timing be off a smidge causing the fuel to be injected too late resulting in an incomplete burn?
Thanks for the suggestions.

That's very possible. We advanced the timing as far as we could until it was up against the stop. It smoked less as we advanced the timing.

I'm haven't been at that boat in a while but I don't think it has glow plugs. I guess that means the compression has to be checked through the injector mount holes. Any suggestions on a compression tester adapter? I have a compression test kit that works fine on my Universal/Kubota via the glow plug holes.
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Old 02-06-2021, 09:27   #5
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Re: Smoking Perkins 4-108

Did you check the valve seats and guides and lap when you pulled/reinstalled the head? This can also lead to poor compression and smoking (usually white smoke though) didn't see what color smoke...
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Old 02-06-2021, 09:36   #6
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Re: Smoking Perkins 4-108

Yes, we took it to a machine shop to have a valve job done and upon disassembly in the machinist said the valves were in excellent shape, they must’ve been serviced recently. The smoke is kind of dark, definitely fuel rich.
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Old 02-06-2021, 20:21   #7
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Re: Smoking Perkins 4-108

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Originally Posted by Quadrille in JB View Post
Yes, we took it to a machine shop to have a valve job done and upon disassembly in the machinist said the valves were in excellent shape, they must’ve been serviced recently. The smoke is kind of dark, definitely fuel rich.

I'd second the compression test suggestion. No sign or bore scoring when you had head off? Just thinking possible cracked ring/s with runaway. Have you tried cracking each injector line nut to see if you have a sick cylinder?
If its blowing black smoke that can be from low compression too as you get only partial fuel burn.
This is all assuming inj. shop did a good job on inj. pump & injectors.
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Old 03-06-2021, 02:53   #8
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Re: Smoking Perkins 4-108

The bore looked clean with no scores and it didn't look like it was glazed. The boat's been in a big state of disarray as the owner is attempting to do too many projects at once so it hasn't been in a state to take it out for a run. Hopefully we can do that in the next several weeks and run it fairly hard to see what happens.
Thanks again for the suggestions and comments,
Bill in JB
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