Starting a diesel

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Packer fan

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Hi,
We have a relatively new to me Nordic tugs 37 with a cummins 6BTA and I know that you should not crank the starter for very long so that water doesn't back up into the turbocharger and cylinders. My question is what is too long and how long do you have to wait after before reattempting? A secondary question would be the same thing for the generator. The gen actually can be a little stubborn to start and I will be addressing that in the next while.

Thanks ahaid of time,

Jim
 
How long is too long really depends on the exhaust system design. On my generator, for example, I can crank as long as I want without flooding it. Even with a water lift muffler, the geometry is such that it'll push water out the exhaust while cranking, so the muffler doesn't over-fill and lead to flooding. I don't know if that's the case for my engines, but in 35 years, nobody has ever flooded them from too much cranking.


If the system is prone to filling up while cranking, it's not just a "wait before trying again", you'd need a way to drain the water out of the muffler before the next attempt.
 
I would suggest asking your question of the boat's manufacturer. The answer might even be in the owner's manual, but you should be able to call or email them.
 
rwidman said:
I would suggest asking your question of the boat's manufacturer. The answer might even be in the owner's manual, but you should be able to call or email them.
Click to expand...

Good suggestion. Please correct me if I am wrong! Only they can answer that because they know the engine and muffler setup. Yes?
 
Well, either the manufacturer or a legit mechanic who can inspect the system and look at the rise in the exhaust, etc, and help you estimate the risk, teach you to drain it, and advise you how it can be retrofitted to make it easier for you to drain when needed.
 
Should not really need to worry about it unless something is wrong.

A healthy diesel should start within a few revolutions, and this is a non-issue. If it does not start, like from air loading or whatever, just go close the sea cock before cranking it a lot. Then DO remember to reopen it once it starts!!

It all depends on how the exhaust is laid out, the various elevations. If highest point of the muffler outlet is higher than the mixing elbow, you need to be careful. If mixing elbow is the highest part of the exhaust system, no worries at all.
 
If you're going to maintenance that requires a lot of cranking, shut the seacock.
A diesel needs 3 things to start. Fuel, compression, and enough heat generated in the cylinders to auto ignite the fuel. That means the rings/cylinders have to have enough compression to raise the internal temps to above 500F. As air is compressed, the temperature rises. In really cold weather, you may need to use a block/pan warmer, or preheat the incoming air with a hair dryer.
 
We don’t have water lift mufflers on our mains so the water drains right out instead of backing up into the engine. So it depends on your muffler.
 
Ski's answer is exactly dead on. You're asking the wrong question. Also what kind of generator do you have? Many require you to hold the start button even after it has started. Many have a preheat function that is on the bottom side of the rocker switch.

Your 6BTA should fire right up unless you are in a really cold area. They do have intake gride heaters. Some don't like them but I do believe they help when working properly. You can turn the "ignition" on and let it sit for a bit with the alarms blaring. You will note a significant draw on the ammeter indicating the grid heater has activated. My current CTAs actually have a light that comes on when the heaters activate so it all depends on the panel setup. Let it warm for a little bit. It really isn't like glow plugs but it will help a bit to warm the intake air and will help a bit in starting.

Also, an issue I had on one of my 6BTAs was that there was not enough current reaching the start stop solenoid so it was slow to open. I thought I was having serious compression issues. But it was totally random and inconsistent and would even happen on a warm engine. So you may want to check that if the symptoms are "irregular". If so, all I did was clean the connections on everything related to that and never had an issue again. Fired right up. Dead of summer?....immediately at starter engagement. Completely cold soaked in dead of (Texas) winter, 3 seconds cranking max....and smokey as hell.
 
My John Deere starts instantly if it receives fuel. I always fuel-prime the engine if not used recently.
 
My waterlift muffler is below the waterline so I could easily fill it and the cylinders with constant cranking. I disconnect the water hose at the exhaust elbow and spill it into the bilge if I have a problem. If I close the seacock and it starts the impeller disintegrates. Not doing that again.

The wait between attempts is to allow the starter to cool off and not overheat. If your engine hasn't started coughing after three 5 second attempts you might want to bleed the secondary.
 
I would like to thank all of you for your reply.

I called Nordic tugs as suggested in one of the posts and they said that it is BS that there exhaust will fill with too much water if cranked for a long time. Maybe others would have a problem. It kind of makes sense because the air coming out of the engine along with the water should push out the water already in the exhaust.

The mention of the startup procedure for the generator is also well taken. I will be studying the manual for it to make sure I'm starting it properly.

Thanks again
Jim
 
"I called Nordic tugs as suggested in one of the posts and they said that it is BS that there exhaust will fill with too much water if cranked for a long time. Maybe others would have a problem. It kind of makes sense because the air coming out of the engine along with the water should push out the water already in the exhaust."

Call again , speak to a different expert.

The combustion of the fuel heats and expands the air and fuel in the cylinder , which is the source of the energy required to lift water from the lift muffler into the exhaust pipe .

Folks would no be offering advice about lift mufflers unless there was bad experience with their operation.
 
FF said:
"I called Nordic tugs as suggested in one of the posts and they said that it is BS that there exhaust will fill with too much water if cranked for a long time. Maybe others would have a problem. It kind of makes sense because the air coming out of the engine along with the water should push out the water already in the exhaust."

Call again , speak to a different expert.

The combustion of the fuel heats and expands the air and fuel in the cylinder , which is the source of the energy required to lift water from the lift muffler into the exhaust pipe .

Folks would no be offering advice about lift mufflers unless there was bad experience with their operation.
Click to expand...


It all depends on the system layout and as a result, how much force it takes to push the water up over the top. In some cases (like my generator), the airflow from cranking is enough to do it and avoid the muffler filling up. In other cases, you won't get water all the way through until the engine actually starts and exhaust gas volume increases.
 
NL gen-set has a limit of 60 seconds. After that, the water in the muffler will back up and you will be sorry.

But as ski said, if it takes 60 seconds, you have other problems.
 
Hi Jim,
I recently sold my NT 37 with Cummins 6BTA. They are, in my opinion, great boats with great engines. Ski gave you a good answer. The info I remember is generally don't crank longer than 60 seconds. Both my generator (Onan) and engine always started within a few seconds. I installed an oil pan heater (250 watts) on the Cummins, and except when at anchor leave it plugged in. This makes for easy starts and keeps the smoke at startup way down.
The air preheat system can be an issue. On many boats, the system stops working (no actual preheat) because the magnetic switches can overheat and fail, connections can work loose overtime, etc. Also, this heat system is designed to operate in an "off and on" manner until the engine reaches either a set rpm or temperature (as a "pollution control" measure). When cycled on, the draw can put a huge load on your alternator which can be problematic especially if operating other high draw items at the same time (like bow thruster or anchor windlass). This system operates "automatically". So I installed a control switch so I could "shut off" the air preheater after the engine started.

For starting, turn on the key and watch your voltage guage on the dash. It will dip down quite low. Wait for the needle to "jump" to the right indicating that the preheat just shut off, and then push the start button. The engine should fire in a couple of seconds.
If your generator has glow plugs like mine did (Onan), push the start button and hold it down until the engine starts. The starter will not engage until the glow cycle is complete and the engine should start within a few seconds of the starter engaging.

For much more info on your Cummins engine check our Tony Athens' website for his business Seaboard Marine in California. He is a well respected diesel expert and freely shares lots of information under "Tony's Tips" and in the various "forums" on his site. sbmar.com
Hope that helps. PM me if you have any specific questions.
 
What FF is trying to say is just because they are from Nordic Tug and answers the phone does not make them an expert. Especially if their tone was “that doesn’t happen on our boats”. It’s a very common “issue”. One most boats can suffer given the wrong circumstances. I don’t care who told me what. I would never indiscriminately crank my engine for long periods of time without addressing this issue. Obviously there are other issues to be addressed if you have this issue.
 
I have two NL 8kw units with glow plugs. They start easily with a cold engine with 15 seconds of preheat before cranking. If you don't pre heat it takes lots of cranking. Check if you have glow plugs to see if they are operational.

On the cummings use the grid heater for about 15 seconds and they keep it on while cranking if you can. Stop after about 10 seconds max and let the heat soaking the pistons and surrounding walls and repeat the process after about 30 seconds waiting. Check to see if the grid heater is functional.

Flooding as noted in the past posts is design dependent on the installation.
My old volvo MD11 was slow to start in the winter. It took about 15 seconds of cranking then you waited about 30 seconds and then would start on the second cranking. It had about a 17 to 1 compression ratio and needed the extra to get it going. No grid heater or glow plugs. It would start immediately with some warmth in the block. Key if you have a grid heater or glow plugs use them for a preheat if the engine is cold. The NL generators start best when using the glow plugs for each start.
 
it should start after 1 turn unless in arctic, then use preheat.
K.I.S.S
Fix the engine starting problems, not the effects.
Apologies to be abrupt but its better to be abrupt than confused by BS.
 
"I have two NL 8kw units with glow plugs. They start easily with a cold engine with 15 seconds of preheat before cranking. If you don't pre heat it takes lots of cranking. Check if you have glow plugs to see if they are operational."


This is common on engines fitted with pre combustion chambers.
The combustion pressure in the chamber seldom gets hot enough to fire the fuel , so starting assistance is needed almost 100% of the time.


Either a preheat glow plug or a tiny squirt of ether does the job.
 
I agree, if it does not start immediately, figure that out first. I can't even hear mine turn over because it starts instantly. Granted it is not that old, but if cranked more than a couple seconds, even when cold, it would be unusual and concern me.
 
firehoser75 said:
Hi Jim,
I recently sold my NT 37 with Cummins 6BTA. They are, in my opinion, great boats with great engines. Ski gave you a good answer. The info I remember is generally don't crank longer than 60 seconds. Both my generator (Onan) and engine always started within a few seconds. I installed an oil pan heater (250 watts) on the Cummins, and except when at anchor leave it plugged in. This makes for easy starts and keeps the smoke at startup way down.
The air preheat system can be an issue. On many boats, the system stops working (no actual preheat) because the magnetic switches can overheat and fail, connections can work loose overtime, etc. Also, this heat system is designed to operate in an "off and on" manner until the engine reaches either a set rpm or temperature (as a "pollution control" measure). When cycled on, the draw can put a huge load on your alternator which can be problematic especially if operating other high draw items at the same time (like bow thruster or anchor windlass). This system operates "automatically". So I installed a control switch so I could "shut off" the air preheater after the engine started.

For starting, turn on the key and watch your voltage guage on the dash. It will dip down quite low. Wait for the needle to "jump" to the right indicating that the preheat just shut off, and then push the start button. The engine should fire in a couple of seconds.
If your generator has glow plugs like mine did (Onan), push the start button and hold it down until the engine starts. The starter will not engage until the glow cycle is complete and the engine should start within a few seconds of the starter engaging.

For much more info on your Cummins engine check our Tony Athens' website for his business Seaboard Marine in California. He is a well respected diesel expert and freely shares lots of information under "Tony's Tips" and in the various "forums" on his site. sbmar.com
Hope that helps. PM me if you have any specific questions.
Click to expand...

Thanks,
This has been the best guidance I have heard yet. I heard of the dont crank it too long because of the water issue but never could get a time limit. I didn't know if it was 5 seconds or 5 minutes. The preheater explanation was very good also. I was told to turn the key and wait for the voltage to drop and then go up again. I had no explanation for why but I thought it didn't have glow plugs. So that was a great explanation. The engine has started for me after maybe 2 seconds. But once I stopped cranking too soon and had to do it again. Thus I didn't have a clue what was too long and didn't want to do any damage.
I am scheduled to get it out of storage this next weekend and am hoping the weather is good enough. So far so good, but forecasts aren't always great 5 days out. I am looking forward to learning more.

Thanks again,
 
Packer fan said:
Thanks,
This has been the best guidance I have heard yet. I heard of the dont crank it too long because of the water issue but never could get a time limit. I didn't know if it was 5 seconds or 5 minutes. The preheater explanation was very good also. I was told to turn the key and wait for the voltage to drop and then go up again. I had no explanation for why but I thought it didn't have glow plugs. So that was a great explanation. The engine has started for me after maybe 2 seconds. But once I stopped cranking too soon and had to do it again. Thus I didn't have a clue what was too long and didn't want to do any damage.
I am scheduled to get it out of storage this next weekend and am hoping the weather is good enough. So far so good, but forecasts aren't always great 5 days out. I am looking forward to learning more.

Thanks again,
Click to expand...


A 6bta should start within 3 seconds of cranking if not 1 second whether the pre-heaters are connected or not (you should disconnect them and forget about them unless you are in Alaska in the winter time)..
 
I have to agree with another reply here. The engine should start after just a few revs. If it does not you have an issue that needs attention.
 
Packer fan said:
Hi,
We have a relatively new to me Nordic tugs 37 with a cummins 6BTA and I know that you should not crank the starter for very long so that water doesn't back up into the turbocharger and cylinders. My question is what is too long and how long do you have to wait after before reattempting? A secondary question would be the same thing for the generator. The gen actually can be a little stubborn to start and I will be addressing that in the next while.

Thanks ahaid of time,

Jim
Click to expand...
Our Perkins 4.236 usually starts in one revolution, in the tropics. Our Onan 8 kw genset starts in just a few revolutions IF you use the glow plugs.
Make sure neither engine of yours is designed with glow plugs and if they are, that they work.
No properly timed diesel should take more than a few revolutions to start in all but the coldest weather, so if there are no glow plugs, get someone to check the compression before moving on to other options.
 
Jim,
PM me with your email address if you want to talk Nordic Tugs. Also, if you are interested, I could send you a Word file of the "owner's manual" that I "put together" from various sources including Nordic Tug factory and other owners. I also have a lot of other research to do with various systems on board that I could share as well. However, not everyone is as interested in this much info, as they feel it just 'bogs' them down.

If you are not interested, just don't respond, no problem.
 
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