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Old 12-09-2014, 12:52   #1
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Perkins 4.108 making oil

Ok, here's my tale of woe. This will be kinda long, but i want to give you gurus all the possible info.

A few weeks into our three month journey we discovered a diesel leak coming from the high pressure fuel pump. Turns out the idle adjustment valve (anti stall device?) had basically cracked off. After dumping 10s of gallons of diesel into the bilge we limped into the nearest service centre and managed to get a temporary fix by epoxing (JB Weld) the piece together. Turns out the pump had probably been repaired like this in the past AND also turns out we may have had a small diesel leak for years.

Anyway, we get back underway and all is fine for a month. Then suddenly we see a big increase in the oil level, along with a pressure drop. Limp into yet another marina. Mechanic diagnosis it as the lift pump membrane, and so after much ado we install a new lift pump. Problem solved once again.

Two weeks later (today) the oil level is way up again. Mechanic (by phone) says the only other possibility is a seal at the high pressure pump which feeds into the block.

I buy that. Makes sense. But why the sudden change? We check oil every day before departure, and we're constantly monitoring oil pressure while motoring. It was great until the first occurrence, where we rapidly went from normal oil and pressure to a flood of diesel and dropping pressure. Same just happened today.

My confusion is not so much the problem. I think it is the pressure pump. My question is why we are able to run fine for many hours of motoring with no problem. Then suddenly WHAM. Diesel floods in.

Here's my theory: We've had a small diesel leak for years which has meant lower pressure at the point where the pressure pump joins the block. With the fix we created higher pressure. But as long as there is sufficient oil pressure it prevents fuel from breaching the gasket or membrane or whatever it is that separates the fuel from the sump at the pressure pump. But if oil pressure drops the fuel is now allowed to enter.

Make any sense? Other ideas? I know most of you are far smarter about this stuff than I.




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Old 12-09-2014, 14:14   #2
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Re: Perkins 4.108 making oil

Negative. It just would not work that way. If the oil pressure is dropping it is because it's already diluted. There is not even a passage from pressure fuel into pressure oil. The drive gears are splash lubed.
I had a mechanical lift pump fail in just 6 months once , so that would not be a big surprise.
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Old 12-09-2014, 15:37   #3
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Re: Perkins 4.108 making oil

Mike, I had a runaway on a Perkins from a pin hole in the lift pump diaphram (sp?) , I was out cruising and could not get a replacement for less than Mega Bucks. Local shop rebuilt it and it lasted 2 or three weeks before it packed up. Luckily without a runaway. Went to a local auto parts store and bought a 12 volt fuel pump, and it was still working perfect 3 or 4 years later when I sold the boat. No more fear of a runaway. A few years later with a Perkins powered backhoe, I had a lift pump failure and went straight to the auto parts store and bought a 12 volt pump (Napa Auto). It still works fine 8 years later. I started carrying a 12 volt pump with me on deliveries. It will at least isolate your problem if you go to electric, and it makes it easier to bleed your system when you need to. It is not at all unknown for fuel to leak past the seal on the main shaft of the injector pump. It can dilute your oil, and new lift pumps wont cure it, but if you get fuel in the oil after you have switched over to an electric pump, you know where the problem is. Keep us posted. ______Grant.
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Old 12-09-2014, 16:13   #4
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Re: Perkins 4.108 making oil

Long shot.. Is it possible to have a fuel return blockage or restriction causing overpreasure in the fuel system and the series of leaks as a result?
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Old 12-09-2014, 17:14   #5
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Re: Perkins 4.108 making oil

If lift pump diaphragm okay, check injector pump shaft seal. Only other culprit would be diesel leaking past the rings, but that's a long shot usually. I have a Perkins and they are, hmmm, interesting. There are shops that will help out with something as touchy as the injector pump. Good luck!
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Old 12-09-2014, 17:18   #6
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Re: Perkins 4.108 making oil

Sorry to hear you're having issues yet again Mike, I hope you can get this cleared up quickly and cheaply!

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Quote:
Originally Posted by Mike OReilly View Post
Ok, here's my tale of woe. This will be kinda long, but i want to give you gurus all the possible info.

A few weeks into our three month journey we discovered a diesel leak coming from the high pressure fuel pump. Turns out the idle adjustment valve (anti stall device?) had basically cracked off. After dumping 10s of gallons of diesel into the bilge we limped into the nearest service centre and managed to get a temporary fix by epoxing (JB Weld) the piece together. Turns out the pump had probably been repaired like this in the past AND also turns out we may have had a small diesel leak for years.

Anyway, we get back underway and all is fine for a month. Then suddenly we see a big increase in the oil level, along with a pressure drop. Limp into yet another marina. Mechanic diagnosis it as the lift pump membrane, and so after much ado we install a new lift pump. Problem solved once again.

Two weeks later (today) the oil level is way up again. Mechanic (by phone) says the only other possibility is a seal at the high pressure pump which feeds into the block.

I buy that. Makes sense. But why the sudden change? We check oil every day before departure, and we're constantly monitoring oil pressure while motoring. It was great until the first occurrence, where we rapidly went from normal oil and pressure to a flood of diesel and dropping pressure. Same just happened today.

My confusion is not so much the problem. I think it is the pressure pump. My question is why we are able to run fine for many hours of motoring with no problem. Then suddenly WHAM. Diesel floods in.

Here's my theory: We've had a small diesel leak for years which has meant lower pressure at the point where the pressure pump joins the block. With the fix we created higher pressure. But as long as there is sufficient oil pressure it prevents fuel from breaching the gasket or membrane or whatever it is that separates the fuel from the sump at the pressure pump. But if oil pressure drops the fuel is now allowed to enter.

Make any sense? Other ideas? I know most of you are far smarter about this stuff than I.




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Old 12-09-2014, 17:18   #7
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Re: Perkins 4.108 making oil

Go buy a 12V diesel inline pump and bypass the lift pump. Run the engine for a a few hours to see if your still making oil. If not replace the lift pump again. A side arm electric pump is a nifty thingy to have and not big $$$. Any auto parts should have it (12V low pressure diesel pump)

If your still making oil have the injector pump rebuilt as you have leaking seals on the injectors

You could run the engine from a 5 gallon jug for a few hours and see if its making oil too.

You can try cracking each HP injector line at each injector to see if one drops out less. One or more should be weak

Best of luck to you.
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Old 12-09-2014, 18:08   #8
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Re: Perkins 4.108 making oil

Quote:
Originally Posted by Mike OReilly View Post

Here's my theory: We've had a small diesel leak for years which has meant lower pressure at the point where the pressure pump joins the block. With the fix we created higher pressure. But as long as there is sufficient oil pressure it prevents fuel from breaching the gasket or membrane or whatever it is that separates the fuel from the sump at the pressure pump. But if oil pressure drops the fuel is now allowed to enter.

Make any sense? Other ideas? I know most of you are far smarter about this stuff than I.




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any excess pressure in the pump housing is returned to the tank, doubt there is a significant pressure drop as a result of the anti-stall leak. The HP pump has it's own built in transfer pump as well. As others have mentioned, there is no back pressure from the oil in the crankcase, When you pull the injection pump off the block, no oil comes out. You can confirm by checking your dipstick position vs pump location.

I would bet a dollar against a dog turd that it is the lift pump again. I too have replaced the lift pump with an electric. Connected thru 3 way switch-ignition/off/on. Makes bleeding simple and I have a small stopcock that I can pump small amounts of clean diesel for projects.
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Old 13-09-2014, 06:24   #9
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Re: Perkins 4.108 making oil

Thank folks. So, I'll definitely be installing the electric lift pump. Sounds like the consensus opinion is that my theory is bunk (no surprise) and that it could be our NEW mechanical lift pump as the source of diesel ingress. I find it seemingly long odds that a new pump would crap out in less than 25 hrs of motoring, but it's obviously possible. A bypass 12 v pump would confirm this.

Thanks for all your help. I'll update as the mystery unfolds.


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Old 13-09-2014, 08:00   #10
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Re: Perkins 4.108 making oil

mike--- make sure you have a really goood pump rebuilder look at your injector pump and injectors also. in usa it will be 1800 usd. here it was 200 usd.
mine ranaway due to similar problems you ar enow facing. good luck and may you find peace with yours and good longevity
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Old 13-09-2014, 12:51   #11
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Re: Perkins 4.108 making oil

Thanks Zee. Wish I was in Mexico!


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Old 13-09-2014, 14:17   #12
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Re: Perkins 4.108 making oil

One very important thing about external fuel pumps-- be CERTAIN output side
hose can NEVER COME DISCONECTED. Also,if it does,pumped fuel will collect to a tank.I have seen this ocur a few times-twice to burning vessel.

All the Best.
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Old 13-09-2014, 20:15   #13
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Re: Perkins 4.108 making oil

If the engine has a LOT of hours, it could be blow by, or injectors leaking...
ring wear..

dp
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Old 17-09-2014, 13:54   #14
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Re: Perkins 4.108 making oil

So the mystery continues. We just motored for 3 or 4 hours with NO problem. But just prior we were making oil (diesel into the crank case).

The chronology and symptoms go like this:

A couple of weeks ago we left anchor and after about 45 minutes I noticed oil pressure was continually dropping. It always drops as the engine heats, but this was going below low-normal. We stopped and found the oil level on the stick to be about 3x higher than the max line. We had checked oil level before starting the engine that day and it was fine.

We limp into Port Dover, have ~7 litres of oil/diesel removed, install a new lift pump and fill with 30 weight oil. All good.

Engine runs great for another ~12 hrs, and then four days ago during our pre-start checks we find the oil is once again way up the dip stick with the same oil pressure drop.

We change the oil, removing about 7 litres once again (so there must be at least 3 litres of diesel in there) and run for about 1.5 hrs. After that time there was some increase measured on the dip stick. We took out ~4.5 litres of oil/diesel so there was probably about 1 litre of diesel in the oil.

Refill with 30 weight, and then motor another 3 hrs. Just checked and oil is fine. Going down, as per normal!!

Other facts:

- We had that idle adjustment device on the injector pump fixed with epoxy (JB weld). The pump was not removed.

- We had an oil leak, but that was coming from the remote oil filter cap, and seems unrelated.

- we have a small diesel leak in the return line. Seems to produce no more than a few spoonfuls over many hours, but it is dripping over the block.

- today I took apart the old lift pump. I could see no perforations or problems with the gasket. Locking bolts all seemed snug. Mechanism seemed to work. As you know though, I'm not much of an expert. It's possible I missed something.

Apparently there are only two places diesel can enter the crank case; at the lift pump membrane or via the gearing shaft on the pressure pump. But in both cases you'd think the problem would be consistently there. Our problem is beginning to appear intermittent. There is about 1200 hrs on the engine hour meter. She seems to run well.

Thoughts? Are there any tests we could perform?

My current theory is that there is a specific RPM that sets up a vibration which somehow let's diesel through at the pressure pump. The only other thing I wonder about is oil levels. I believe we've not had problems when the oil levels are high.


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Old 17-09-2014, 14:06   #15
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Re: Perkins 4.108 making oil

I don't see how a lift pump could be intermittent. By gasket, do you mean the diaphragm looked fine? No tears around the center rivet?
The fuel injection pump could be intermittent. Internal pressures at different rpm could cause a seal lip to move and then leak. If you took off the pump you would probably see some sign or smell around the drive gear.
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