Lombardini 6LD - Sluggy's got a problem

[Diesel Dave]

So the first time ever in our 150,000 mile relationship, old Sluggy's got a problem and I can't seem to solve it.

Motor starts fine and sits there idling away, pull the throttle and nowt happens.

I've had the primary and cases off a dozen times so far and can't see anything wrong with the regulator or controls.

The centrifugal balls are free to move, both the main regulator spring and the extra fuel spring are in place, the rack are moves freely and has been set in position according to the workshop manual (centrifuge bell closed and arm to full fuel). I've tried moving the arm so that it's slightly less but this causes the motor to run at full pelt and can't be killed on the controls - I had to crack the nut on the high pressure injection line to kill it.

So far I've replaced the injector pump and the injector (just because I had new ones available).

I'm getting to the point where I'll drill the cases and fit a control cable directly to the rack arm - I suspect this will work.

The throttle cable pulls the regulator spring OK - just seems not to have any effect?

Any help gratefully received.

[coachgeo]

sounds like a link/connecting rod or something is missing or allowing movement independently instead of moving what it is suppose to move.

[Diesel Dave]

Well after replacing every component in the system the problem persisted, it's the first time Old Sluggy's been a problem over our 150,000 miles together.

So after applying a little head scrathing and a tad of lateral thinking I've bypassed the regulator system and gone for direct control of the pump by the throttle and it works.

I still need to set an over-fueling limit as it's possible to put way too much juice resulting in (as our American Truckers would say) "Making coal".

But at least the old boy should be good for the next 150,000 miles

Keep the faith
DD

[tappy]

I'm really interested in that. Are you finding any hunting at idle or anything?
Very interested to hear where you end up with that.

[coachgeo]

..........So after applying a little head scrathing and a tad of lateral thinking I've bypassed the regulator system and gone for direct control of the pump by the throttle and it works............DD

With out pics.......... it didn't happen!

Seriously though........ a write up along with pics on how you bypassed things some may find very interesting

[alexanderfoti]

+1 for interested in pics

[Diesel Dave]

Ok Ok I'll post some piccies up in the morning.

[Diesel Dave]

Ok here goes..... may be difficult to follow but....

So here's a photo of how the direct pump control rod exits the casings (yes I drilled a hole)



Doesn't tell you a lot does it......

So what's going on inside?

Firstly a bit of background.

There are basically 2 main parts to the throttling control and then are not directly connected, only through the influence of spring tension, when you pull on the throttle it increases the tension in this spring and allows the motor to rev higher.

A really crappy diagram:



So the bit on the left has 2 shafts, one attached to the throttle cable and this pulls a spring connected to the second shaft. At the end of the second shaft is a fork that engages with the pump operating shaft - this shaft also operates as the engine stop by pulling the throw to min on the pump (no fuel).

On the right we have the shaft that connects to the pump by a long arm, in the middle is the fork that engages with the centrifuge and on the other end is the arm with a pin that will be operated by the throttle as detailed in the previous paragraph.

Concentrating on the latter arm as this has direct influence on the pump:



These are the parts all mounted on the same rod.

if you were to push downwards on the pin this would rev the motor higher, however we need a pull throttle so..... add another piece and...voila:



So by pulling on this arm we get direct control of the pump....

Of course I have left all the original throttle control bits in place as this sets the idle nicely, however this system also bypasses the Max Fuel (max rack) setting so at the moment it's smoking like a good 'un. Watch this space for the next thrilling episode where this problem gets fixed.

[coachgeo]

centifuge operating arm; Is that the name of that whole rod or the name of that squared U shaped piece?

[Diesel Dave]

The u shaped bit, as crank speed increases the centrifuge pushes against the bottom of that arm.

[coachgeo]

The u shaped bit, as crank speed increases the centrifuge pushes against the bottom of that arm.

it pushes it upward? Increased crank speed makes a tiny piston rise to push against it; such as via increasing oil pressure orr???

[coachgeo]

.....
So what's going on inside?....[/url]

So the bit on the left has 2 shafts, one attached to the throttle cable and this pulls a spring connected to the second shaft. At the end of the second shaft is a fork that engages with the pump operating shaft - this shaft also operates as the engine stop by pulling the throw to min on the pump (no fuel).

On the right we have the shaft that connects to the pump by a long arm, in the middle is the fork that engages with the centrifuge and on the other end is the arm with a pin that will be operated by the throttle as detailed in the previous paragraph.

Concentrating on the latter arm as this has direct influence on the pump:...
These are the parts all mounted on the same rod.

if you were to push downwards on the pin this would rev the motor higher, however we need a pull throttle so..... add another piece and...voila:...

So by pulling on this arm we get direct control of the pump....

....

You say "pump" many times above so just for clarity; this refer's to "injection pump" each time and nothing related to fuel pump whose sole purpose is to pull fuel from the fuel tank to the IP for pressurizing and injecting at correct times?

[Diesel Dave]

Yes I refer to the injection pump, little stationary motors being gravity fed unless a lift pump was needed for a specific application.

[Diesel Dave]

The u shaped bit, as crank speed increases the centrifuge pushes against the bottom of that arm.

it pushes it upward? Increased crank speed makes a tiny piston rise to push against it; such as via increasing oil pressure orr???

See if this helps:

[alexanderfoti]

aha that makes sense to me. Seems like it should work well.

[coachgeo]

ahhhhhhh......... so when centrifuge pushes it causes the shaft to "rotate" and swing the lever toward less fuel.

Thanks.

[Diesel Dave]

Ok so after a little experimentation I've found that the throttle pull was too short when acting directly on the new rod attached the the fueling rack.

So in order to allow for increased throttle cable movement I've made up a little lever system:



So the throttle cable pulls about 3x more cable than the rod moves.

Seems to work well, although I've got a slight problem of hanging on to rev's when the throttle is released, it really needs a stronger return spring but that's the only one I had in the 'magic box of all sorts of possible useful crap'.

[henneberg]

Hi,

Nice movement gearing. BTW - which kind diesel fuel filter(s) are you using ?

Erik

[Diesel Dave]

Hi,

Nice movement gearing. BTW - which kind diesel fuel filter(s) are you using ?

Erik

It's just a cheap plastic fuel filter, the bicycle valve on top is epoxied in place so I can bleed air out of the line.

[Diesel Dave]

Finally finished the external pump control system by adding a max fuel stop to the lever.



Also needed to add an extra spring the the throttle cable, the throttle stop is the M6 cap head screw behind the cable.

Job done.

[skoleskibe]

It's just a cheap plastic fuel filter, the bicycle valve on top is epoxied in place so I can bleed air out of the line.

Do you happen to run out of juice often ?

[Diesel Dave]

I do forget to fill up...

Usually around the Thursday of the second week of commuting without a refill