Rough first start? stumped

[lamadriver]

OK,

SO recently this developed . SO I go to start the engine and it takes a long time ot turn over then it idles real rough. ( too low ) 400 +-. Scary rough motor is just jumping on the mounts unitl you give it some more fuel.

It helps if you start with throttle in neutral giving it a bit of extra throttle position forward. If you do this and bring it back to neutral it idle's where it should at 650 ish and turns over quicker

You turn off the motor and go to start a second time , It immeaditily cranks over and goes right to where it should at 650+- rpm...... no need to induce more fuel

Whats going on ...

Its not fuel, all filters have been checked / changed

Why does it only do it on the first start and only if you dont give it extra throttle when you go to start it ?

All the able positions look correct. I veen disconnected the cable and it did the same thing?

Thoughts?

LD

[JPA Cate]

Maybe there's some other load on the engine when you first start it. I'd try giving it more revs for 2 or 3 minutes, and see how it does.

Ann

[Wotname]

Originally Posted by lamadriver

OK,

SO recently this developed . SO I go to start the engine and it takes a long time ot turn over then it idles real rough. ( too low ) 400 +-. Scary rough motor is just jumping on the mounts unitl you give it some more fuel.

It helps if you start with throttle in neutral giving it a bit of extra throttle position forward. If you do this and bring it back to neutral it idle's where it should at 650 ish and turns over quicker

You turn off the motor and go to start a second time , It immeaditily cranks over and goes right to where it should at 650+- rpm...... no need to induce more fuel

Whats going on ...

Its not fuel, all filters have been checked / changed

Why does it only do it on the first start and only if you dont give it extra throttle when you go to start it ?

All the able positions look correct. I veen disconnected the cable and it did the same thing?

Thoughts?

LD

What engine is this????

Reading between the lines it seems that you are describing "hard to start when cold".

What is the ambient temperatures your location?

Are there any glow plugs or air heaters on this engine?

If everything else is equal, hard cold starting may be due to starter motor / electrical issues or low compression issues - think valves or rings or worse.

We need more detail before knowing how to help.

[Suijin]

Originally Posted by lamadriver

OK,

SO recently this developed.

In addition to the engine make/model, and info that WOT requested, some more info around when this started and your prior experience with the motor. How long have you owned the boat, usual pre-start procedure, etc.

I agree that it sounds like simple cold starting. Old Universals for example specify that you energize the glow plugs for 30+ seconds before cranking, and with the throttle advanced when you. If not it'll run rough and lumpy until you give it more fuel. In summer when it's 80 degrees you can get away with 5-10 seconds...in winter when it's 35 anything less than 30 seconds is inadequate.

[sailorboy1]

It's normal for my engine to like to have some neutral throttle for start-up when it completely cold. I think it just fuel related from being off a long time and the extra rpms gets the system back to pressure. Otherwise it is just not running fast enough to both supply the engine and get the fuel fully at pressure.

[SV Bacchus]

Diesel engines run off heat, no spark plugs so the engines high compression = heat needed for ignition. Older engines can lose some of their compression due to wear = harder starts and rougher idle. However, once the engine has some heat, as in some warm up, it idles better and starts easier.

[Iaangus]

It could be a few things, You mentioned filters were changed, if there is a leak anywhere in the fuel supply line including a filter it can allow air to enter the system. if a few drops leak out somewhere a little bit of air can be sucked in at the injector. This air at the fuel atomizer / injector act a a cushion for each pulse of fuel. At idle the tiny pulse of fuel is not large enough to overcome the cushion of air. when you give it more throttle the puse of fuel is larger and faster and purges the air. The same problem can also arise with a bad injector allowing leakage. Another possibility resulting in same symptoms could be a faulty check valve usually mounted near where fuel enters the filter is allowing fuel to drain back to the tank when engine is shut off for a considerable time. again air is drawn in through the injectors to replace fuel draining back to the tank. This usually only happens when fuel level is lower than the filter level. Another possibility is that the fuel shut off wether mechanical or electrical is not returning to run position when it should be. If your engine shuts off when you turn a key off it is an electrical shut off. They are usually all or none. A pull knob, (maybe they are not even used in a marine engine) would be mechanical. With a mechanical shut off they need to be adjusted to return to start position when the knob is pushed in. These are all easy fixes, hopefully one of these fixes your problem.

[Arthur Garfield]

Agree with other posters,not enough data though.Has ambient temp dropped?-Prolly cold-use glow plugs at ambient to see if continues.Often dirty injector tips could have same effect.Fuel quality?Try running fuel with an injector cleaner.Rev it out to see also if it settles back to smooth at normal idle speed.


All the Best

[Trekker]

Sounds like classic glow plug malfunction, either not being used (or aware that it needs to be), or malfunction. Glow plugs do go bad & can be easily checked for proper operation. Fix to either is easy and cheap so I'd check this out before getting upset about a non-existent major problem.

[topmast]

My old Ford does that too Small air leak back at filter makes first start rough. and takes a day of sitting before this situation happens again .Return must go to tank or it just builds up to be a non starter.

[lamadriver]

Awesome.

Thanks for all the replies. "Hard to start when cold" is what I was trying to relate.

Its a vetus 4.17 ( mitsu block). I have owned it for about 1200 hrs. it has 1500 hours on the engine.

This all started after the engine had sat for 7 months in the yard. Like i menitioned before as soon as there is some heat on it it cranks right over and goes to right to where it should idle wise.

1) Ambient temp: Tropics - but heading to really cold places hence the concern.

2) I have been holding the key to down to ensure glow plug warming. ( Ill get those things checked) I can hear the electric lift pump ticking away as well.

3) the injector bit crossed my mind - I have a spare set and the boat is now in a place that when i return i can get them cleaned.

4) I check the voltage at the starter and the battery and it looks ok. - there is no load on the engine

%) I dont think it is a leak at the filers as I changed the filter after this started , but will double check.

I am away in Alaska working, though I can make arrangements to have this trouble shot in South Africa as time will be limited when i get back.

Any suggestion on what I should ask so the trouble shooting is efficient, because as soon as the mechanic starts the thing it will be a day before the problem can be replicated?

test glowplugs, check for air leak? compression est?

Thanks for all the help.

LD

[Quebramar]

Suggest you make a small video of this cold start so your technician can see how it behaves

[boatbod]

Small air leak in fuel system?

Usually even an engine with low compression will run fine immediately you get it started, so I'm more inclined to think you have a fuel problem.

[Wotname]

Originally Posted by lamadriver

Awesome.

Thanks for all the replies. "Hard to start when cold" is what I was trying to relate.

Its a vetus 4.17 ( mitsu block). I have owned it for about 1200 hrs. it has 1500 hours on the engine.

This all started after the engine had sat for 7 months in the yard. Like i menitioned before as soon as there is some heat on it it cranks right over and goes to right to where it should idle wise.

1) Ambient temp: Tropics - but heading to really cold places hence the concern.

2) I have been holding the key to down to ensure glow plug warming. ( Ill get those things checked) I can hear the electric lift pump ticking away as well.

3) the injector bit crossed my mind - I have a spare set and the boat is now in a place that when i return i can get them cleaned.

4) I check the voltage at the starter and the battery and it looks ok. - there is no load on the engine

%) I dont think it is a leak at the filers as I changed the filter after this started , but will double check.

I am away in Alaska working, though I can make arrangements to have this trouble shot in South Africa as time will be limited when i get back.

Any suggestion on what I should ask so the trouble shooting is efficient, because as soon as the mechanic starts the thing it will be a day before the problem can be replicated?

test glowplugs, check for air leak? compression est?

Thanks for all the help.

LD

I would check the glow plugs first, especially the wiring and all aspects of the their circuit. I'm thinking some corrosion or similar has occurred while sitting on the hard and one or more glow plugs aren't working or only working partially (i.e. not hot enough). They are pretty easy to check.

The low revs and rough running is indicating that only a couple of cylinders are firing initially.

[LarsKessel]

If your yacht is in Cape Town try Charles Barker. He works from RCYC and sorted out my Yanmar 2GM which had exactly the same issues. Turned out to be the govenor...