Perkins 4.108 making oil

[Mike OReilly]

Thanks Guy, there were no perforations in the diaphragm of the lift pump that I could see, although I am far from a trained mechanic (as you can tell). I plan to have the injector pump removed and either rebuilt or completely replaced. Hopefully that will solve the problem, Your info on the differing internal pressures makes sense, and fits with the differing RPM idea. Thanks.


Why go fast, when you can go slow

[sailorchic34]

Interesting problem. So have you checked that the return line to the diesel tank is clear???. The external leak, might be due to a restriction in the return line, either at the tank or collapsed hose to the tank.

Increased back pressure could causes the seals to leak at the injector pump.

Agree that the lift pump either leaks or it doesn't.

You mentioned a leak at the remote oil fill and pressure at the dip stick. Is that as in oil seeping out around fill cover. If so verify that the crankcase breather is clear (hose from valve cover to air filter housing). If it is clear, you have a wee bit of blowby. It is slightly possible the excess crankcase pressure could cause the seals to leak in the injector pump (via oil return line from external pump)

[sanibel sailor]

The return from the chamber of the high pressure pump to the tank should be at low pressure, seems a leak would not be too likely. Is there a restriction in the return line that might explain the leak and cause higher internal presure in the pump, driving fuel past the seal into the crankcase? I might pull the hose and blow it out to be sure.

[Cheechako]

I have had this problem in a perkins (although it was consistent). It turned out to be a bad injector. That cylinder wasn't firing and the injector was washing the rings and fuel going into the oil. The engine seemed to run fine and I only discovered this by cracking off the injector nuts and noticing the one cylinder made no difference. A compression test showe one bad cylinder after that.
Coincidentally, a pushrod popped off the rocker arm also. either before or after the injector failure. probably related in some way. At any rate, you can see if a pushrod is off by removing the valve cover. I would crack those injectors and see if one cyl is not firing first. after the pushrod and injector were rebuilt the compression came back In that cylinder.

[model 10]

Originally Posted by sanibel sailor

The return from the chamber of the high pressure pump to the tank should be at low pressure, seems a leak would not be too likely. Is there a restriction in the return line that might explain the leak and cause higher internal presure in the pump, driving fuel past the seal into the crankcase? I might pull the hose and blow it out to be sure.

That sounds like a good idea

[zeehag]

mike--sounds like what i was finding, despite words otherwise from my alleged mechanic, as i checked all he did, you are describing what i found.
take off both pumps. find a builder of same and have em done. injectors also.
check exhaust elbow for carbon. the next thing as mine deteriorated was the coloring of my fuel to black. oops. next was the flushing from system via exhaust a buncha black oily carbony stuff and some smoke, then runaway and seizure. two injectors were bad. all 4 have been replaced or rebuilt.
i should have had my injector and lift pumps rebuilt before i left usa, but i got a muuuch better price on them being rebuilt here and by a better mechanic.
as of now, both pumps and entire engine and all injectors are essentially brand new.

[Mike OReilly]

Thanks for all the great ideas folks. Much appreciated. I'll take a look at the return lines and make sure there are no obstructions. It is leaking at one joint, but that seems to be due to a dried grommet that Perkins uses. I've heard a few mechanics complain about them. I will look though.

Interesting idea about the bad injector, but you'd expect this to be a consistent problem, wouldn't you? It appears we are sometimes running just fine, with no diesel intruding in the oil, and then other times when we get a flood of diesel in a very short time. I hate intermittent problems...

I'm going to get the injector pump rebuilt or replaced, so we might as well test all the injectors as well. And I'll for carbon buildup at the exhaust elbow.

I'll keep you posted.


Why go fast, when you can go slow

[zeehag]

just a thought--- if you use an electric assist pump and keep it on during running of engine, you CAN bypass the lift opump, as i found i was doing.... might want to make a toggle switch for that, if you have one, so you can switch iot off during passages anbd general engine use and save it for the priming.

just a helpful hint from hell -ow -eeze

[HappyMdRSailor]

Mike,

I'm liking the restricted return and the leaky injector too... Albeit agreed that the intermittent occurrence is mind bogglingly FRUSTRATING!!!

You gotta admit though... You got one HELLA CLEAN crankcase if you can keep her in one piece until you figure this thing out!

[Mike OReilly]

Originally Posted by HappyMdRSailor

...You gotta admit though... You got one HELLA CLEAN crankcase if you can keep her in one piece until you figure this thing out!

So true! We've done more oil changes in the past three weeks than the rest of the five years I've owned the boat. The oil is actually looking very clean, compared to the sooty black I'm used to seeing.


Why go fast, when you can go slow

[ctl411]

Check your return line hoses. They can "break" internally causing a blockage. I've seen this happen to brake hoses. This would fit the intermittent problem.

[Capt Gill]

Originally Posted by Mike OReilly

So true! We've done more oil changes in the past three weeks than the rest of the five years I've owned the boat. The oil is actually looking very clean, compared to the sooty black I'm used to seeing.


Why go fast, when you can go slow

Mike, did you get it fixed? I'm having what seems to be the same problem. I drained 8 litres of engine oil/diesel from the crankcase. I've narrowed down the diesel ingress to the crankcase to the most likely suspect, the lip seal in front of the HP pump. I'm going to recheck the lift pump then use its pressure to check for leaks while the c/case is empty.
The engine runs smoothly at idle and cruising speed so I don't think it's a defective injected(s) that would dump that amount of fuel.
Silver lining: the engine insides, like yours, are getting a good cleaning.

[Argyle38]

I'm curious as well as this thread popped up last year when I was researching why I ended up with a bunch of diesel in my crank case.

When it happened it was an unusual situation. Just topped the fuel and had to use pretty much full throttle to try to spring off of the fuel dock we were getting pushed on to by a significant breeze. So topped off fuel and full throttle at a high load allowed a bunch of diesel in to the oil.

Changed the oil and adopted a wait and see approach. Didn't have an issue motoring mostly down the US ICW, about 300 or so hours of run time. Had other engine problems (head replacement) which necissitated another oil change and the oil didn't appear to have diesel in it, just based on volume and smell.

Now the problem seems to have re-occured. Drop in pressure with an increase in volume, although this time it was probably only about 1L diesel at most but it was noticed at are relatively low "slow cruise" rpm.

When it first happened I also inspected the lift pump, which I had replaced a few years earlier. It looked good but took the unit apart and applied sealant to the surfaces and re-installed. The diaphragm still looks perfect and there was no evidence of diesel on the "oil side" of the diaphragm.

Also thinking that it's a seal on the HP injector pump.

Additional question, since I'm likely to be removing and re-installing this injector, is this seal something that requires a whole pump rebuild or is it something that I can replace pretty easily? I'm mostly a DIY guy but I'm not interested on rebuilding an injector pump. I will send that out. But if the seal in question is more or less easy to access and replace, that would save me from having to spend a month of dead time at a maria.

[Mike OReilly]

Kinda a blast from the past... I see I failed to complete the story. My bad .

Yes, we managed to get the problem solved. It involved having the injector pump rebuilt, which was, and still is, way above my diesel pay-grade. This definitely fixed our problem.

As the story went, we initially changed out the lift pump because apparently that is the most likely culprit. This seemed to work at first, but the problem came back, so we ended up biting the bullet and getting the injector pump rebuilt. This was no small feat in that we had to first remove the coolant system to get to the pump. And with all the twisting and cranking, we managed to contort a number of high pressure diesel lines which causes micro-cracks and therefore leaks.

We spent two months tracking these new leaks down AFTER we got the rebuilt injector reinstalled. It was a major PITA. But that was many years ago now, and it has run perfectly ever since. Sadly the oil quickly returned to black. The nice diesel cleaning didn't last too long.

[skipmac]

Gee, glad to see this thread pop up. My boat is fine but my diesel tractor is having the same problem. Bought a new lift pump but when I pulled the old one it appeared to be in perfect condition so dropped the project and went to do boat jobs instead.

Maybe time to get back to the tractor. Just as soon as I finish all the jobs on the boat.