Question for the diesel engine specialists

[BartW]

That's interesting stuff. The turbo air tapping to the fuel pump is probably just a rate limiter on acceleration, to prevent overfuelling (black smoke).

yes, it adjusts the amount of fuel that is send to the cylinders, and in relation with the available turbo pressure.

we have measured and compared turbo pressure on both engines,
and up to 2100 rpm they are the same on each engine,

when one engine does 2300rpm, and the other does 2150 rpm, the latter has less turbo air output pressure.(which seems normal)

after the tests it was made very clear that the difference is in the pumps !
the bad pump had the problem in Trogir....

 

[MapisM]

So, in other words, whatever is regulated by the turbo pressure, is embedded inside the pump - which is consistent with the fact that the problem follows the pump.
Now, if your question is whether those 150NM with the hose disconnected could have damaged the pump, I have no clue.
Since you said that you made the whole trip at 1100rpm, I wouldn't think that the pressure which should have gone through that hose was relevant... Bu what do I know?
Anyway, next week I'll mention also this to the MAN specialist I told you about!

 

[BartW]

So, in other words, whatever is regulated by the turbo pressure, is embedded inside the pump - which is consistent with the fact that the problem follows the pump.
Now, if your question is whether those 150NM with the hose disconnected could have damaged the pump, I have no clue.
Since you said that you made the whole trip at 1100rpm, I wouldn't think that the pressure which should have gone through that hose was relevant... Bu what do I know?
Anyway, next week I'll mention also this to the MAN specialist I told you about!

yes,
thanks !
I made a whole list of questions for Ilko, to discuss with the Bosch service office,
and potential (re-) calibrations, done with the pump in place, or eventually back out again.
TBC

 

[KevB]

Having the pressure pipe left off maybe something has blocked the pipe or the vacuum inlet on the pump?

 

[BartW]

Having the pressure pipe left off maybe something has blocked the pipe or the vacuum inlet on the pump?

indeed, this is one of my potential causes of the problem,
but I can't find a logic explanation as I don't know any details from the interior mechanism of that pump


during the tests, there was a temporary turbo air pressure gauge installed, (same pickup point as that hose to the pump)
on this gauge we could read that at low rpm; there is a air "underpressure" in that meaurement point,
so at low rpm there is a resistance in the airflow from the non turning turbo.
I'm not sure if running the engine with the "underpressure" hose missing, might have changed something in the pump.

ofcause when doing more rpm, the turbo starts to turn, and that air pressure becomes positive, and increases linear with rpm.

 

[MapisM]

during the tests, there was a temporary turbo air pressure gauge installed, (same pickup point as that hose to the pump)
on this gauge we could read that at low rpm; there is a air "underpressure" in that meaurement point, so at low rpm there is a resistance in the airflow from the non turning turbo.
I'm not sure if running the engine with the "underpressure" hose missing, might have changed something in the pump.

Makes sense.
As long as the engine is running like a normally aspirated one (i.e. with the turbos not yet spinning fast enough), it's bound to create some depression.
Do you remember around which rpm the pressure became positive?

Anyway, also based on what you are saying now, I still see no reason why the pump could have suffered any damages from those 150NM at 1100rpm.
Basically, during that time with the hose detached, the pump was constantly sensing just the atmospheric pressure, which by definition must fall within its designed operation range (from somewhat low depression up to 2 bar or whatever).
But again, I'm saying this based on just a tiny bit of technical knowledge, on top of a lot of common sense...

 

[Eren]

wheneven I come to sell the boat, how would I explain to a future buyer;
that one engine doesn't hit 2300rpm, but apart from that the engines are like new ????

Fully agree with that !

 

[BartW]

Fully agree with that !

it was good to meet you Eren,
hope to see you again in PM

 

[BartW]

Makes sense.
As long as the engine is running like a normally aspirated one (i.e. with the turbos not yet spinning fast enough), it's bound to create some depression.
Do you remember around which rpm the pressure became positive?

Anyway, also based on what you are saying now, I still see no reason why the pump could have suffered any damages from those 150NM at 1100rpm.
Basically, during that time with the hose detached, the pump was constantly sensing just the atmospheric pressure, which by definition must fall within its designed operation range (from somewhat low depression up to 2 bar or whatever).
But again, I'm saying this based on just a tiny bit of technical knowledge, on top of a lot of common sense...

yes, I'm also at that stage with my thinking about the problem,
I've send all my questions regarding the pump service to Ilko,
lets see what he comes up with.

 

[Eren]

it was good to meet you Eren,
hope to see you again in PM

Likewise Bart!

It was very inspiring to see the additions and improvements you made to your lovely Canados.

We will catch up again in the season I believe.

Wish you good luck with the pump issue.

 

[gordmac]

I would be surprised if there wasn't some sort of throttle stop on the pump, have you tried adjusting it (not the fuel adjuster)?

 

[BartW]

I would be surprised if there wasn't some sort of throttle stop on the pump, have you tried adjusting it (not the fuel adjuster)?

yes that was exactly my thought,
and we found a screw that stops the max excursion of the throttle lever, (straight on the pump)
but the MAN guy who did the rebuild didn't want to touch that.
I have to admid that this screw had quite a few of layers of paint, and wasn't touched "ever" so to speak

now we need advice from someone who knows these mechanical "line" pumps,

the MAN guy agreed to go ahead with it,
but his relation with the Bosch service center who schecked that pump is very unclear ...

thanks for posting

 

[rafiki_]

Bart, have you tried a PM to Latestarter!? Haven't seen him on the forum for ages though.

 

[BartW]

Bart, have you tried a PM to Latestarter!? Haven't seen him on the forum for ages though.

no not yet,
he hasn't posted anything since november last year, I hope he is ok.

 

[NormanB]

Let's assume the fuel pump service is carried out fully compliant with the manufacturers spec on the bench and that includes some sort of datum for 'idle' position on the fuel rack quadrant.

That would be a simple set to work situation in a single engine scenario, once installed to ensure consistent start and idle conditions and thereafter that the max fuel position was not exceeded.

However in a twin engine installation there just has to be set to work instructions to achieve load balance between the engines, once connected to throttle controls correctly (and we are reasonably confident the throttle control is fine because the problem follows the pump). Any adjustment you do make will affect idle and top end conditions as fuel rack rotation is essentially linear and so a bit of jiggery pokery involved. Usually there is a set position that involves the use of a setting dowel or a slip gauge or similar.

As I opened much earlier in this thread, I am not familiar with your engine(s), but the procedure I allude to must be well documented for your engines - somewhere.

I will be interested to learn of the successful outcome.

It must be infuriatingly frustrating for you.

 

[rafiki_]

he hasn't posted anything since november last year, I hope he is ok.

Yep, I echo your thoughts.

 

[BartW]

However in a twin engine installation there just has to be set to work instructions to achieve load balance between the engines, once connected to throttle controls correctly (and we are reasonably confident the throttle control is fine because the problem follows the pump). Any adjustment you do make will affect idle and top end conditions as fuel rack rotation is essentially linear and so a bit of jiggery pokery involved. Usually there is a set position that involves the use of a setting dowel or a slip gauge or similar.

As I opened much earlier in this thread, I am not familiar with your engine(s), but the procedure I allude to must be well documented for your engines - somewhere.

remember this is a very old installation,
the throttle and gear controls are hydraulic, and there is quite some play and hysteresis on them
and there is absolutely no system for synchronising or balancing the two engines,
when accelerating, usually I move the 2 throttles with two hands,
and I have an eye on the rpm gauges that both engines accelerate more or less simultaniously, thats all,
usually I accelerate fairly slow with this big old machine.

But,
with the current situation, it feels as if the faulty engine/pump reaches full throttle before the other,
actually on the good engine/pump I can continue to give a bit more throttle and subsequently more rpm,

this phenomen is on "the other" engine since swapping the pumps,

 

[NormanB]

Any developments Bart?

 

[Piers]

some on here might remember that I had a complete overhaul done on both my MAN diesel engines,

both engines run very smooth, with little but normal smoke for these old mechanically injected 12cyl. engines,

One engine gets to normal 2300rpm max,
BUT the second engine only gets max 2170rpm.

We had the boat lift out, clean hull and props,
difference was the same,

Yesterday a team op 3 ppl spend the whole day swapping the injection pumps from the two engines.
and this morning again sea trial,
now the lower rpm is on the OTHER engine,
so its the injection pump that creates the difference for max rpm.

a year ago, both pumps have been send together to Bosch (in Koper Slovenia) for refurbishing, so actually it is their responsability.

but the MAN service Guy's are a bit in doubt if its worth finding the last
130Rpm ???
also as the pumps are really old, (its cam shaft might suffer a bit of wear)
the two engines run perfectly smooth up to that speed, and I will never ever run the boat above 2100Rpm... and its a big job to get that pump out one more time.

any advice from the specialists on here ?

Hi Bart,

Having a difference would really annoy me and I'd want it sorted out. By swapping the pumps between engines and finding the problem swaps as well, is proof to me, that something wrong with the injector.

Which injector is at fault is the question. Why do I say this? If the difference occurs during a sea-trial, it could be that the pump on the engine which revs higher is at fault so the slower engine is under greater strain.

BUT, in my mind, if you have injector pumps refurbished, they are brought back to new status with no wear on any parts. Calibration graphs and certifites should be provided as proof.

So, even if I was never going to use the top revs, the difference would annoy me and I'd keep going to final resolution.

 

[superheat6k]

I don't remember seeing this thread first time around.

From your initial description you have isolated the problem to the pump. This seems to me to be a governor setting issue. Correct operation of the governor on a conventional jerk pump engine is crucial. The throttle on these engines works in direct association with the governor by increasing the governors set position as the throttle is opened. This is completely different mode of control to a flap or variable Venturi on a carburettor. All the throttle is doing is demanding more revs, not power.

An important feature is that the governor is controlling the speed of the engine, per given throttle setting. Ok so speed is also affected by load, so with a dirty hull or fouled props then it might not achieve the desired speed, but that is down to the power the engine develops at any given throttle setting. Why am I banging on about this, because at minimum load, I.e gearbox in neutral, the engine should achieve its designed max revs, and no more at WOT. It should never be possible to over speed a Diesel engine.

You mentioned that you had not tried full rev tests. This would be my next check. First with the engine stopped move the throttle control to WOT position and check the position of the control lever on the pump governor, and compare this is reaching the same place on the good engine. If this is not achieving as much speed demand then this could be the issue, but assuming this is correct, then, in neutral, engines both thoroughly warmed up, slowly increase to WOT, and note the max revs achieved.

If the under revving issue remains then time to check the governor settings, stuck flyweight, catch, etc. If the engine achieves WOT then the pump is delivering insufficient fuel under load. I would send it back to a Bosch agent for recalibration, but first do check there are no gauses or filter screens anywhere that could have become choked up.

Of course it is some while since the thread so you may have resolved your issue, if so I would be interested to know what was discovered. My own fuel cut off solenoid issue recently had me stumped for months.