Red Hot

[mobile_bob]

have you checked the injector?

is it dribbling and not firing cleanly?

timing too fast?

too much exhaust system back pressure?
what is your exhaust temp getting up to under max loading?

seems to me it ought to pull near 3kwatt with the heater without
issues.

time to dig into the tougher to diagnose possibilities, perhaps?

iirc correctly is this the engine that was cooking the oil on the underside of the piston?
and when it gets hot the engine acts like it is starting to sieze the piston? getting too tight?

i am thinking you may well have a bad injector that is not firing properly, overfueling
and not atomizing properly enough to get a clean burn and makeing a bunch of heat?

can you pull the injector and have it pop tested by an injection shop?

you have several things happening
1. the engine won't pull the full load
2. it is making some smoke, moreso than you feel is normal
3. it gets hot and acts like the piston is getting tight.
4. the oil is coking on the underside of the piston top

sure makes me wonder about the injector, timeing and exhaust back pressure
in decending order.

i do know that DI engines when an injector tip fails can burn a piston in a hurry
being your engine is IDI it keeps most of the heat from direct contact with the piston.

not an easy one for sure

bob g

[oliver90owner]

Lendusaquid,

Remind us - does it run on thermosyphon or pump?  A pump draws power and will reduce system output by about 150W

Lister spec, remember only gives 6HP on the dot at 650RPM.  Any reduction will mean less than 6HP (probably losing about 200W output from this).  How are you measuring RPMs? It may make a bigger difference.  If using a tacho, how did you check the calibration?

Operation of your COV: Is it in or out?

Indian piston: Is the ring gap correct?  Are the rings able to sit below the piston OD when installed ( like - are the grooves too shallow?)  Is this the engine which had a bent crank?

What efficiency is the generator at that output?  An oversized head could be well down on efficiency.

Having said that, if it is not getting hot, not black-smoking, not losing RPMs it doesn'r seem to be at the power limit for it's operation.  One way is to accelerate it at full load - does it simply belch black smoke and not increase speed or does it pick up speed easily?

Is this running on bio or dino?

Bob has listed most of the regular check points from the manual

Am I right in thinking you had a tight piston at TDC a long time ago?  If so what has changed to remove that fault?

Was the ring ridge removed properly when fitting new rings? Is the top ring higher than on the original piston?

Did you clean away all deposits under the rings when you found the piston gummed up recently?

It sounds as though you are likely to have a serious failure if the engine continues to run improperly.

Regards, RAB

[lendusaquid]

Its running on thermosyphon into an insulated copper cylinder.I get about 2 hours running before thermosyphon fails.Using a laser tacho to measure rpm.Also used a bicycle tacho to double check.COV out at 3kw on diesel and veg.For my last run it was diesel only.Ring gap is about 20 thou.All the rings can be pushed below the surface of the piston.It had a bent conrod  not crank.I had straitened the conrod but replaced it anyway.Its running an ST5 head which has had the fan end bearing replaced.This is the engine with tight piston at TDC and cabonised oil under the crown when at full load.This is still the problem.I had a new dry liner fitted and the piston is Indian so there is ,or i should say was no ridge.Injector was tested by Bosch about a year ago.I do get carbon around it when running veg even when it is heated to above 100C.I have tried ajusting the timing either way because iam not quite sure which way to go,especially when trying to get rid of diesel knock.Exhaust is one thing i have not thought about.At the moment i have it going through a lorry silencer and then down into a underground pit.I will remove the silencer and pit and replace with just a pipe for testing.If that fails then the piston is coming out and i will put a propane torch to the crown to see if anything happens.I have an old Lister piston that i will also try although the top groove is to slack to use a ring.I never seem to get much smoke except when overloaded just like any lister. What effect would having a worn pump cam have ?       

[mobile_bob]

if you have been running veggie i would have the injector retested
the more i think about it the more suspect i am of the injector being the culprit in this issue.

as for a inj pump cam issue, i suppose anything is possible but seems unlikely that it would cause
overfueling, alter the timeing maybe,, but i doubt it is causing your problem, but check it out anyway.

you mention carbon on the injector tip, how do you clean that off?
with a cloth and solvent or with a rotary wire brush?

the reason i ask is a rotary brush can deform the tip hole(s) and cause a bad pattern

if it is not too much trouble pull the injector and have it rechecked
make sure it pops cleanly at the spec'd pressure and does not dribble under partial pressure

be sure of the guy you have checking it, these old mechanical injectors are gettin long in the tooth
and most of the new guys are working with electronic units and may think that your pattern/operation is
good enough and maybe not really good enough?

also you mention a dry liner
is it a thin liner that does not have contact with the coolant? like the 71 series detroits and mack engine's?
if so you may have clearance issues between the block and liner allowing oil to get up between them carbonize
and effecitively insulate the liner from the cooling system.
how tight did the liner fit the casting? press fit, chilled fit, slip fit, sloppy fit?

i am not familiar with early listers and what they did with liners or if in fact they were dry liners, but if they
are you really want to look into this and have a proper fit.

i am reaching at straws here, don't know your engine, and can't see it either, so take it fwiw

just trying to help

bob g

[lendusaquid]

Ill get the injector retested to be on the safe side.The old liner was pressed out and a new one pressed in.It has no contact with the coolant.When i first phoned the company that carried out the work and told them what it was, he immediately looked up  the required  spec, which impressed me.The guy had worked on the things in the way distant past.

http://www.robinsonengines.adsl-web.newnet.co.uk/

I have checked alignments and levels every which way i can think of.All i have found so far is that the top of the piston is on a slope and its obvious by sight.More bump clearance on one side than the other.
Having more than one person clutching at straws is more than welcome.For a start i never thought about the exhaust back pressure.

[lendusaquid]

Stripped the engine down and rebuilt it. Ive got a suspicion that i might have got the gears one notch out when doing some previous work.Also found more than one copper washer in the injector hole,so now the injector sits lower down where it should be.Exhaust temp is about 200 C. Any advise on whether this is about right or not?.Appears to be running sweet on 2.8kw. Had my first key fall out as well.The flywheel was pulled towards the engine by the belt which was lucky. 

[mobile_bob]

your exhaust temp seems about right to me for a lister/oid
that works out to about 390 degree's F. which seems good to me

it now carries the load you want with it, so cool!

maybe it was a one tooth advanced cam?

glad to hear it is doing more in line with what it should and meeting your expectations

have you ran it long enough under the 2.8kwatt load to see if it acts like it is getting tight again?

my thinking it is not getting tight now?

hope this solves the problem for you.

bob g

[lendusaquid]

Ran it for a couple of hours on diesel and all seems ok to me.Tighter than when cold but i expect it to be.Not excessive like before thou.Bit concerned that the small end pin on the Indian piston can be pushed out with a finger.On the Lister pistons i have, it has to be knocked out.Even sloppier when hot i should think.