Perkins 4 108

[Biscay 36]

Fuel oil is getting into the engine oil, not in great quantities and only intermittently, three times in the last 200 hours. I have a fuel tap on the day tank which gravity feeds the injection side and I mostly turn it off when the engine is not running; the leak off pipe goes back up to the day tank. The last time the problem occured was after a filter clean and change when I left the fuel tap open for some time before bleeding the system. The system has been in place for several hundred hours before this problem started. My search here came up with, lift pump seal, injection pump seal or a dribbling injector but would that account for the intermittent nature of the problem? Any other suggestions would be welcome?

 

[Heckler]

Fuel oil is getting into the engine oil, not in great quantities and only intermittently, three times in the last 200 hours. I have a fuel tap on the day tank which gravity feeds the injection side and I mostly turn it off when the engine is not running; the leak off pipe goes back up to the day tank. The last time the problem occured was after a filter clean and change when I left the fuel tap open for some time before bleeding the system. The system has been in place for several hundred hours before this problem started. My search here came up with, lift pump seal, injection pump seal or a dribbling injector but would that account for the intermittent nature of the problem? Any other suggestions would be welcome?

If it was the fuel lift pump then it would happen when the engine was running and in fact that is the classic symptom of a perforated diaphragm.
So I would be looking at a seal on the lo pressure side of the inj pump. The injector dribble? mmm, dont think so. It would have to be very badly damaged to let lo pressure fuel through.
Stu

 

[Biscay 36]

Thanks for the advice. Its a lowline engine and to get at the injection pump means taking the manifold off I suppose. Ah well!

 

[Roberto]

same problem

have had the same problem to my 4108

I changed the lift pump, but the problem continued; not a lot just one leak every 100ish hours, but it then became more frequent. The leak happened only when the engine was stopped.
I had the injectors serviced, but the problem continued. It was leaking also with the fuel tank shut off, litres of fuel into the oil sump.

I eventually found it was a leak from the return pipe into the tank: fuel syphoned back through the return pipe into the injection pump then the oil sump.
I had the injection pump serviced and now it is working like a charm -again :smile:

 

[Biscay 36]

"I eventually found it was a leak from the return pipe into the tank: fuel syphoned back through the return pipe into the injection pump then the oil sump." You mean it was going from the tank to the injection pump via the return pipe and the injection pump was leaking it into the sump? Is it a tricky job to take the injection pump off?
Thanks

 

[Roberto]

You mean it was going from the tank to the injection pump via the return pipe and the injection pump was leaking it into the sump?

indeed, strange as it may seem, it took me one month to figure out the cause.
The sequence was:
oil check before starting: ok
engine running uo to 24hours (moroccan coasts without wind :grin: ), oil pressure and level ok
engine stopped: oil level ok

two days later: pre departure oil check and I found 5-8 litres of fuel/oil mixture inside the sump

I got the suspicion from a big leak (several litres) with the engine stopped and after I had shut the fuel tap off: where the hell could all that diesel come from ??

My return fuel pipe goes deep into the tank, and as I usually keep the tank rather full that meant the return pipe was dipping into the tank diesel: as long as the engine was running no problem whatsoever, vice-versa once stopped, as the tank is a little higher than the engine, the diesel leaked back through the return pipe into the injection pump, where a leaking seal let it go into the sump

Is it a tricky job to take the injection pump off?
Thanks

It took a mechanic about two hours to take it off, longest affair is disconnecting all the fuel metal pipes, and also (golden advice I am giving you) have at hand an imperial 7/32" allen key for the third bolt of the injection pump, the one hidden between the engine body and the pump body. Most 4108 have the same type of bolt, I do not know about yours but keep that in mind anyway.


Before taking the pump off, be sure to have it marked (if it is not marked yet) like in this picture: there are two marks, one under the F letter on the engine body, and a corresponding one on the pump flange; if they are kept aligned when mounting back the pump you will not have to spend one day to dismantle half the engine to get the right pump timing back

I like working on my engine, but after having seen the mechanic work to get the pump off I think I could do that myself next time, but am happy I have not done it the first time

 

[Biscay 36]

Thanks for all that. Are you in Salvador? My boat is up the coast in Jacare, Cabadelo! You can e mail me at alan@airleywight.freeserve.co.uk if you wish.
Alan Hunt
S/Y Blue Biscay

 

[Roberto]

Thanks for all that. Are you in Salvador? My boat is up the coast in Jacare, Cabadelo! You can e mail me at alan@airleywight.freeserve.co.uk if you wish.
Alan Hunt
S/Y Blue Biscay

yes we are in Salvador!

email sent

 

[DownWest]

I had the same problem. But the cause was the injection pump shaft seal leaking fuel into the gear case, then sump. Pump rebuild solved it. I luckily had a spare pump and a sympatico outfit, who combined the bits and saved me mucho on new bits.
A curious result of the mix was that it turned to a jelly like substance that would no longer pump round the engine to lube it. The oil light staying on with a full sump caused me to look hard before it seized. I thought oil pump, until I dropped the sump and found the goo.
A

 

[phantomlady]

We seem to have exactly the same problem!
Do you think it would be possible to move the fuel return pipe - ie put it higher and vent it - as a temporary measure to stop it siphoning back. So we can sort it out when we get home??

 

[Roberto]

We seem to have exactly the same problem!
Do you think it would be possible to move the fuel return pipe - ie put it higher and vent it - as a temporary measure to stop it siphoning back. So we can sort it out when we get home??

If the question is for me, then I would say (things I have done)

1. Check that your tank (or fuel level inside the tank) is higher than the engine, otherwise no syphoning would be possible
2. With a full-ish tank (or with fuel at the usual working level), disconnect the return fuel pipe at a convenient place, then gently blow through it and listen if you can hear air bubble noise inside the tank. In my tank, the return goes from the top of the engine (secondary) fuel filter through a flexible hose to the tank, I disconnected that one and blew air through it, hearing bloupbloupbloup inside the tank. That means the return pipe descends deep inside the tank, at least to be immersed into the fuel, which is a second pre-requisite for syphoning back
3. Disconnect the bolt on the injection pump feeding the return line, and check if it drips diesel

add a leaking injection pump seal and there are all the ingredients for a full oil sump, as it happened to be my case.
I asked the mechanic if there is a non-return valve somewhere on the return line but he did not know, so that may be a possibility

I am no expert, but a syphon-break device put at a sufficiently high position, should protect from such a flow-back

rr

 

[makingplansfor]

I have exactly the same issue with my 4108, the high pressure fuel pump waiting to be refitted after a refurbishment. My question is whether any damage could occur elsewhere in the engine due to significant amounts of diesel making it into the engine oil. The engine has not been run for more than 5 minutes at idle but I am more concerned about whether the diesel could attack any rubber seals or bearing packing. Also, will draining the sump and refilling once adequately purge the engine of fuel?

Any thoughts appreciated

 

[Roberto]

I have exactly the same issue with my 4108, the high pressure fuel pump waiting to be refitted after a refurbishment. My question is whether any damage could occur elsewhere in the engine due to significant amounts of diesel making it into the engine oil. The engine has not been run for more than 5 minutes at idle but I am more concerned about whether the diesel could attack any rubber seals or bearing packing. Also, will draining the sump and refilling once adequately purge the engine of fuel?

Any thoughts appreciated

The mechanic who worked on my injection pump said there is no danger in fuel washing through all the parts where oil should be. He said water would be a completely different matter, with fuel there is less lubrication but no corrosion of parts.
He said.

FWIW, I drained up to 6-7 litres of diesel/oilmixture from my sump. Basically I changed oil and filter, then sailed up to the entrance of the marina and used the engine for 2-3 minute to get to a berth. After 3 minutes, the oil pressure alarm would ring, oil pressure drop to less than 1 (usually 4 on cold engine), and I stopped the engine wherever I was.
There you go, a second oil and filter change to get three more minutes ad the next port; I eventually (about 15 litres ofoil and 4 filters later) arrived where I could service the pump so nightmare over.

After the last change of oil, after having repaired the injection pump, I noticed no diesel smell, no oil dilution, oil kept the transparent colour for the first couple of hours then became the usual black, it seems business as usual to me.
FWIW, I used the engine about 300 hours after servicing the pump and I could not notice anything weird. Same consumption, no smoke, undiluted oil, and oh yes, the usual Perkins trademark oil leak :smile:

 

[makingplansfor]

Hopefully a similar result to come - refitting at the weekend. Oh how I look forward to the normality of sticky black engine oil which once used to concern me.

Thanks for putting my mind at rest.