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Old soul
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Discussion Starter · #1 ·
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.




Why go fast, when you can go slow
 

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islander bahama 24
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I'm thinking you are correct on the location of the leak. The leak is being mostly kept in check by oil pressure some fuel is leaking and reducing the viscosity of the oil and as the fuel degredation is happening there is also an increase in thermal viscosity breakdown causing the fuel leak and degredation to increase which lowers the viscosity and pressure more quick means more fuel leaking in and well you can see where this is going (vicious circle). IMO
 

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No experience with your engine, however, it sounds like your theory may be a good one. Except for the lift pump, I can't think of any other way fuel , in that volume, fuel can get into the crankcase?

Maybe two bad lift pumps in a row?, if not, maybe a removal of the high pressure pump with all new gaskets /seals?

Or, temporarily install an electric lift pump, with the manual pump removed & blocked off with a plate

The Diesel Page, Electric Lift Pump and Racor Filter installation

Paul T
 

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You don't say what the motor is.
You may choose to fit an electrical lift pump separate to the engine to avoid the risk that the lift pump diaphragm will rupture again.
Steward Warner make some good ones and they are not too expensive.
It also has the advantage that air is less likely to be drawn in to the fuel system since it is pressurized. Instead fuel will be seen to leak out and the leak can be seen.
.
 

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Old soul
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Discussion Starter · #6 ·
Thanks folks, I'll get an electric lift pump, but what are the odds of having a NEW lift pump go after only 25 hrs. Surely that points to the pressure pump seal. As you say newhaul, it would create a vicious cycle.

The other interesting fact is with the install on the new lift pump we ended up with slightly more oil in the sump. It was overfilled a bit (didn't account for the filter oil). We let this drop back over the 25 hrs. It's a Perkins so it always leaks some oil, after all.

With the decline in oil, I'm thinking this could have started the decline in oil pressure, which then precipitated the vicious cycle of diesel getting in past the gaskets at the pressure pump or perhaps lift pump (although, what are the odds of having a new pump gasket die in exactly the same way so quickly?).


Why go fast, when you can go slow
 

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Thanks folks, I'll get an electric lift pump, but what are the odds of having a NEW lift pump go after only 25 hrs. Surely that points to the pressure pump seal. As you say newhaul, it would create a vicious cycle.
Never say never. :D

The other interesting fact is with the install on the new lift pump we ended up with slightly more oil in the sump. It was overfilled a bit (didn't account for the filter oil). We let this drop back over the 25 hrs. It's a Perkins so it always leaks some oil, after all.
I would think that as long as the oil pump pickup tube is submerged, the pressure should be the same, regardless of how much oil is in the pan? I think pressure can vary when the oil warms up, or when the engine itself gets hot, allowing for more clearances in the bearings?

With the decline in oil, I'm thinking this could have started the decline in oil pressure, which then precipitated the vicious cycle of diesel getting in past the gaskets at the pressure pump or perhaps lift pump (although, what are the odds of having a new pump gasket die in exactly the same way so quickly?).
As above, as long as the pump is sucking oil, I think the pressure would stay the same? "Odds"? probably pretty slim, but?

The electric pump would be an easy try, & you might decide to make it permanent, or plumb it in as a backup to the mechanical pump?

Let us know how it works out.

Paul T
 

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islander bahama 24
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Mike the one thing you haven't told us is what oil you are using not brand but weight and I would assume it is formulated for diesel engines. Also adding an electric lift pump is a great idea for any engine that may be a long way from repair parts cheap insurance against the most common failure part.
 

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Old soul
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Discussion Starter · #9 ·
Straight 30. Diesel formulated, non-synthetic. It's what the manual recommends. We were using 10w-30 up on L. Superior, but have switched to straight 30 now that we're in the balmy warm waters of the southern Great Lakes.


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islander bahama 24
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Straight 30. Diesel formulated, non-synthetic. It's what the manual recommends. We were using 10w-30 up on L. Superior, but have switched to straight 30 now that we're in the balmy warm waters of the southern Great Lakes.

Why go fast, when you can go slow
OK then I would really start looking at the seals then straight weight oil will cause pressures to go a little higher until it warms up and thins out the multi vis oil is fine and actually recommended over straight weight oils the ten w thirty means it flows like ten weight oil and protects and resists thermal breakdown like thirty weight with old seals suddenly increasing the oil pressure can cause the seals to fail so I have another question does the appearance of the leaking problem corospond with the changeling of oil to the straight thirty weight?
(See where I'm going)
 

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Old soul
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Discussion Starter · #11 ·
I see where you're going but the initial leak of diesel into the case happened before the switch to straight 30, and after the high pressure pump repair. We made the switch when we replaced the lift pump. Ran for ~ 20 hrs before the problem reoccurred.


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islander bahama 24
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OK was the injection pump removed to effect the repair and if so was the pump to block seal replaced also if removed are the bolts properly torqued or have they come loose I'm starting to reach here hard not being there to touch it was it twenty hrs of operation before it reoccured or till you noticed the rise in level.
 

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Old soul
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Discussion Starter · #13 ·
I appreciate your reaching! The injection pump was not removed. The epoxy repair was done in-situ, but I'll check the bolts. Of course it's hard to answer your second question for sure. We are quite diligent about checking the oil level at the start of every day. We motored hard and continually for 9 hrs when going through the Welland Canal. We checked it the following morning and oil was down a bit on the stick, which is normal for our engine. We did not top up bc it was still in the ok zone, and then motored another few hours over two days before noticing first the decline in oil pressure, and then the diesel-infused oil (way up on the stick).


Why go fast, when you can go slow
 

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I appreciate your reaching! The injection pump was not removed. The epoxy repair was done in-situ, but I'll check the bolts. Of course it's hard to answer your second question for sure. We are quite diligent about checking the oil level at the start of every day. We motored hard and continually for 9 hrs when going through the Welland Canal. We checked it the following morning and oil was down a bit on the stick, which is normal for our engine. We did not top up bc it was still in the ok zone, and then motored another few hours over two days before noticing first the decline in oil pressure, and then the diesel-infused oil (way up on the stick).

Why go fast, when you can go slow
A puzzle, indeed. Not having hands on experience with your engine I can't see how fuel from the injector pump could pass into the pan. If the high pressure pump had a reduction in pressure, it may not be able to fire the injectors? Reading back, your first lift pump change immediately solved the problem.

If it was the injector pump leaking back through the block, I would think it would be constant? As removing the injector pump requires re-timing & disconnecting the high pressure pipes, which may leak on re-assembly, I would try the lift pump first?

Maybe something in the mechanical pump alignment? Maybe too much lift from the cam, maybe internal variations in pumps?

Curious to know what the lube oil pressures were/are after you changed oil viscosities?, cold & hot?

Paul T
 

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Old soul
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Discussion Starter · #16 ·
I'll update as soon as I can. We're at anchor right now, but can sail to our final destination where we can get access to parts and probably a pump machine shop. We'll be running the engine for a bit, so may be doing oil changes on the fly. Wish me luck :-(


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.... add to all the above: a cracked or leaking injector pump.

The leak could possible be internal to the injector pump and is either coming out through the 'rack' or through a crack on the periphery of the injector pump body ... and that crack that was repaired on the 'outside' may well be propagating through to the inside into the 'high pressure' areas of the injector pump. That youve already noted a crack on the external of the pump body would tend to increase the index of suspicion that that crack is 'more' than just an external crack.

Rx: Remove the injection pump and have it bench tested, including an eval. for leaks *not normally found* at your local injector shop - ie. "Magnaflux" testing of the pump body.


Just about every large town above population 15000 will have an 'injector shop' or one 'close by'. Before you go the expense of a bench test (pump function) inquire if the injector shop will do the "magnaflux" eval. (pump integrity) before the bench testing, etc. By magnaflux testing I dont mean 'dye penetrant' testing; but, a FULL magnetic crack evaluation - FIRST.
 

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.... add to all the above: a cracked or leaking injector pump.

The leak could possible be internal to the injector pump and is either coming out through the 'rack' or through a crack on the periphery of the injector pump body ... and that crack that was repaired on the 'outside' may well be propagating through to the inside into the 'high pressure' areas of the injector pump. That youve already noted a crack on the external of the pump body would tend to increase the index of suspicion that that crack is 'more' than just an external crack.

Rx: Remove the injection pump and have it bench tested, including an eval. for leaks *not normally found* at your local injector shop - ie. "Magnaflux" testing of the pump body.

Just about every large town above population 15000 will have an 'injector shop' or one 'close by'. Before you go the expense of a bench test (pump function) inquire if the injector shop will do the "magnaflux" eval. (pump integrity) before the bench testing, etc. By magnaflux testing I dont mean 'dye penetrant' testing; but, a FULL magnetic crack evaluation - FIRST.
Good point, however my thoughts keep going back to the first lift pump replacement immediately solving the problem. That sounds like a lot of fuel ending up in the pan? Perhaps a combination of the two?

It will be interesting to see what he finds. I would try the lift pump replacement first, before ripping the injector pump apart.

Paul T
 

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Sure lift pumps break their diaphragms all the time ... easy test to evaluate. Pressurize the delivery line with an electric pump, shut off the tank valve then shut off the elect. pump .... watch the pressure/vac gage on a filter - if pressure holds 'steady' over time with the tank valve closed then patent diaphragm; if pressure drops - pin hole in the diaphragm.
Cheaper than blindly replacing the lift pump.
 
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