At what RPM Do You Start a Diesel ?

[goboatingnow]

Sorry folks petkins 4108 http://users.firenet.uk.com/stewartbray/perkins4108.pdf

I draw your attention to the paragraph " starting the engine" to dispute the nonsense

[cal40john]

Originally Posted by daddle

Whatever you tried to say ... my Bosch fuel injection manual says, I don't make this stuff up: "...when the engine is cranked the plunger will travel through a complete delivery stroke ... giving ... maximum delivery quantity ... Thus the maximum delivery quantity [of fuel] is made available when the engine is cranked."

A nearby graph indicates the starting fuel supplied may be as much as twice the full power amount.

[Source: Diesel Fuel Injection Pumps, Bosch, 1995]

Now as far as the speed at starting, perhaps some engines won't happily idle until warmed up. These may need the speed control adjusted slightly to boost the idle for smooth initial running. Probably most common with tired engines, worn engines with sticky governors, low compression, and the like.

And Bosch calls it an engine-speed control lever.

I think Yanmar does it also, at least the 3GM30. Looking at the governer diagram, there are two arms. The first arm connected to the engine speed control lever through a spring pushes on the second arm which is attached to the fuel rack and the governer flyweights. When the flyweights try to reduce fuel the second arm pushes on the first arm and stretches the spring. But the second arm can move in the increase fuel direction without affecting the first arm. There is a spring on the second arm called the starting spring. So even if the control lever is set at idle, when the engine is stopped the starting spring has the second arm, the one connected to the fuel rack, advanced to full throttle. When the engine starts the flyweights push the two arms back into contact with each other again.


Which engine is the manual refering to that says the fuel is retarded at high throttle settings. It's not obvious how that would happen on the 3GM30 from the governer diagram and I don't remember reading that in my operators manual, but I need to go back and check it.

John

[goboatingnow]

Seahunter I don't know where you got the nonsense, see my post above. Perkins primarily designed industrial engines., these engines ARE designed to start and immediately run to full operating throttle a very common occurrence in generators , pumps, , etc. In no way do you do any ( more) damage on startup in this manner. Slow idle with the block slowly coming up to temp is not a good way to treat a diesel.

Also all my 4108 started after winters layup without any need to 'reprime the lift pump.

Dave

[cal40john]

Originally Posted by goboatingnow

Seahunter I don't know where you got the nonsense, see my post above. Perkins primarily designed industrial engines., these engines ARE designed to start and immediately run to full operating throttle a very common occurrence in generators , pumps, , etc. In no way do you do any ( more) damage on startup in this manner. Slow idle with the block slowly coming up to temp is not a good way to treat a diesel.

Also all my 4108 started after winters layup without any need to 'reprime the lift pump.

Dave

You could be entirely correct, but all the manual you referenced says is to start the engine at full throttle. Lacking any warnings about warming up the engine it could probably mean go ahead and load it up. But this might not be universal to all diesels. In my Yanmar manual it says to warm up the engine at idle for 5 minutes and let it cool down after it has been at load for 5 minutes. It says that the lube oil may not have spread to all main bearings and other moving parts for some time, so idle to protect these parts from wear.

Also I found an operaters manual online for the 3GM30, it says to set the engine control lever at 1/2 throttle to start. It gives no explanation as to why.


John

[wadda]

I started thinking about how I start my 4108.

I start at 1/2 or so throttle. As soon as it catches, depending on the state of the battery, I pop it down to idle until the oil pressure starts to climb. and then I ramp it up to a fast idle that doesn't give a lot of harmonic noise.

When I see action on the temp guage I start to do what I was going to do and try not to really load it until it come up to temp and not beyond.

When I shut it down I'll idle it until I think the engine is equalized or I get impatient.

I tend to use the tach to confirm that it is at the sound/vibration level I think it should.

I tend to run it around 2400 rpms which is 80%, of the maximum continuous rating because I heard that's what you're suppose to do and it is a sweet spot. It just sees to like that speed. I like it as well.

[goboatingnow]

It should be pointed out to be fair., that in an unloaded situation full throttle start should be immediately followed by a reduction on successful starting. I'm not suggesting that the engine be run at full WOT continuously unloaded from cold


Note that the full ( or in some cases partially open settings ) are primarily for cold starts. In normal ambients most diesels will start quickly and run on a high idle setting. ( from cold)

[goboatingnow]

Originally Posted by wadda

I started thinking about how I start my 4108.

I start at 1/2 or so throttle. As soon as it catches, depending on the state of the battery, I pop it down to idle until the oil pressure starts to climb. and then I ramp it up to a fast idle that doesn't give a lot of harmonic noise.

When I see action on the temp guage I start to do what I was going to do and try not to really load it until it come up to temp and not beyond.

When I shut it down I'll idle it until I think the engine is equalized or I get impatient.

I tend to use the tach to confirm that it is at the sound/vibration level I think it should.

I tend to run it around 2400 rpms which is 80%, of the maximum continuous rating because I heard that's what you're suppose to do and it is a sweet spot. It just sees to like that speed. I like it as well.

Nothing wrong with that just that unloaded idling of the engine to temp, while a common usage is in fact not the best way, especially in modern diesels. Once you've verified oil pressure and cooling flow your better off bringing the temp up
Under load. I tend to not leave the boat idling at the dock , but once I'm happy alls is well I motor out letting the work of that under medium revs get the temp up. It does not benefit on any way to slowly warm the engine. In fact in very modern engines the engines may never( or take a very long) to come up to temp , which is why car companies fit little webasto heaters to get the cabin heating working as soon as possible. ( particularly in urban settings)

It's also worth noting that the way probably millions of diesel car engines are used.

Diesels don't benefit from pampering, a good hard life of constant use is best. Most marine engines die of lack of use.

As I've said most diesels are designed to be available immediately upon successful startup, otherwise they'd be excluded from many applications.

Again on cool down engines can be turned off immediately. Turbos benefit from not going from full load to off . Outside of this again a diesel engine does not benefit fr a cool down idle period often many big marine diesels run too cool in near idle speeds causing excessive smoke.

Dave

[meyermm]

Engines start at "0" RPM.

Originally Posted by Seahunter

This might be true of German designed engines built in Taiwan with "Botched" electronics, but Perkins engines were designed and built by the Queens carriage makers and were deliberated over in the minutiae of detail including thread count on each metric screw over a thermos of tea (Ceylon). Perkins engines are complicated only in their all mechanical way of dealing with everything. In the end they managed to put together a fairly simple and dependable way of oiling the bilge while sipping fuel over great distances.

These were my favourite answers after reading the posts

The one about starting up at full throttle but warning that this also meant throttling back after ignition spoiled another good one.
Nothing like a diesel at WOT no load for entertaining the marina.

[Hannah on 'Rita T']

Originally Posted by goboatingnow

Sorry folks petkins 4108 http://users.firenet.uk.com/stewartbray/perkins4108.pdf

I draw your attention to the paragraph " starting the engine" to dispute the nonsense

Our Perkins doesn't have the described MKIII cold start unit. I suspect that was used on diesel tractors in cold climes.

[MarkJ]

Throw the dock-lines off.
Push the throttle FULLY forward.

Let 'er rip!

[sailorboy1]

I read this earlier and was going to give what I do and what my manual says.

But assuming the various answers so far come from some of the various engine manuals the answer seems to be; do whatever YOUR engine manual says to do.

[Unicorn Dreams]

Whar's even funnier at the marina, isn when soneone cranks the engine up full throttle, is when they forgot to put the tranny in nuetral ur have a bad shifter cable.
Watched a skipper do that in an anchorage once, funny watching him cone up the companionway ladder and race back to the engine cinytols at the helm. But sadly, not fast enough to stop before he ran over his anchor rode.
Helped him a couple days later to install starter button in the cockpit and remove it from below.

I always start my Perkins at lowest throttle position unless it's below 60F then I advance the throttle about half an inch...

[David M]

For an old diesel, another factor is the oil pressure. You will probbaly want to rev it up a little so it is not warming up with lower oil pressure. If for example it idles at 600 then perhaps rev it up to 1000. You may also want to rev it up if this is what it takes to excite the field on the alternator so your battery is charging. Check your voltage for this.

[CarlF]

I was once told by a Mack Boring rep that it takes 2 minutes for full oil pressure to come up in all parts and corners of a Yanmar engine lube system - long after the oil pressure light/gauge shows pressure at the sensor. You should keep the revs down until then.

He'd also said that when starting an engine that had not been run for a week or more you should hold in the stop button (Yanmar) and crank the engine five seconds. This gets some lubrication into the cylinders which dry out over time. This isn't an issue with diesels that take a few seconds of cranking normally but many newer engines start pretty much instantly.

Finally, on engines with a turbo you should idle for two minutes before shutdown to let the turbo revs reduce before cutting off the oil supply by shutting down.

Can anyone confirm or deny?

Carl

And Mark, it's a much more entertaining show if you reverse the order of your departure steps - advance throttle to full then cast off. Even better, use a stern spring of disposable cord and ceremonially cut the line.

[David M]

With a turbo diesel that is very true according to Cummins, but for a different reason. Turbines spin down pretty quick and are always spinning so long as there is exhaust flowing through them. What you do not want is for a hot turbine to burn the oil that lubricates it's bearings. A turbine needs a few minutes to cool before shutting down the engine.