Yanmar 2GM20 cranking speed

[misterg]

Got a niggling problem with our 2GM20F - It takes a lot of cranking to get started after it's been left for a while. Once it's been running, it will re-start instantly, even if stopped for hours. Doing a bit of searching, these appear to be classic symptoms of an air leak in the supply to the injector pump (the tank is below the level of the engine). I was quiety confident that I had found the culprit (plug on the top of the secondary filter had a small weep), but after fixing this, and leaving it for another week, it's still the same. I haven't given up on the air leak theory, but would like to ensure that the engine is cranking fast enough - the workshop manual doesn't give a cranking speed, only the advice "Does cranking speed sound slow?" in the trouble-shooting chart. Unfortunately the boat is relatively new (to us) and I've got nothing to compare it against.

So: Does this sound like the normal cranking speed for a 2GM20?

Web page with mp3 file

(Volume is low, so you may need to turn things up a bit)

The starter battery happens to be quite new, and was fully charged - 12.9V. There was ~10.5V at the starter motor whilst cranking.

(Seacock closed until the engine starts; no smoke; Don't particularly want to pull injectors / check squish clearance, but may do this winter if no better.)

Your comments appreciated.

Andy

 

[fireball]

Sounds like it is cranking at the same speed as our Y 2GM20 .... we've found that we have to have 1/2 to 2/3rds throttle and it starts reasonably quickly there after.

FWIW we turn the water on before we try and start - it is quick enough so no problem really. We also find it is much quicker to start after it has been run for a bit.

 

[Honey]

Sounds the same as my 2GM20F. I need to start from cold at full throtle and ease of as soon as it fires to approx 1000rpm for about a minute. This helps to keep vibration down. They do bounce around a bit at tickover.

 

[misterg]

Thanks guys, that's very reassuring. It does start a heck of a lot quicker with a handfull of throttle, but I didn't think that was normal, because it then races up to high speed (no rev counter). The starter button in inside the companionway and the throttle is at the back of the cockpit, so it's a bit of a sprint between the two /forums/images/graemlins/smile.gif

I agree it bounces around like mad at idle, but smooths out once there's a few revs on.

Thanks again,

Andy

 

[Cloven]

Agree with above -yes you need a fair bit of throttle to get it going which is what is recommended in the engine handbook. I use about 3/4 throttle and it starts fine. Also I always start up with the engine seacock open as per Fireball above.

Sounds like you may also have an air leak problem. The only solution is to check every joint from the tank to the injectors. Quite often you can get an air leak in without any signs of diesel "weep". I had this on my primary fuel filter after a new filter was badly fitted by an marine engineer. Eventually I bypassed the filter and the problem was solved. Marina then fitted a replacement and no problems since.

 

[biscuit]

I had a similar "slight" leak from the bolt in the secondary filter, (same engine) which slowly became more than slight & was due to a totally stripped thread on the body of the filter, needing a whole new assembly. May be worth another look?

 

[rob2]

I'm told that part of the slow starting, which appears to be the norm on marine diesels is the use of red diesel itself. It has such a low cetane rating that starting from cold is a nightmare. If you can reach it, full throttle seems best...
Perhaps now we're expected to pay road prices, we'll obey the owners' manual and use decent quality fuel. My car always starts first turn with no throttle. Should that tell me something?

 

[earlybird]

[ QUOTE ]
My car always starts first turn with no throttle. Should that tell me something?

[/ QUOTE ] Assuming it's a diesel, it tells you that, unlike a Yanmar, it has heater plugs.

 

[misterg]

On the red vs white point: It just so happens that the engine is running on road diesel at the moment, as I last filled the tank up from my spare jerrycan. No noticeable difference, and it's used up 1/2 a tank so far.

I've had the bolt out of the secondary filter, and the threads are OK - it tightens up fine - I just had to change the copper washer.

Another point raised by PM was to check that the stop cable wasn't slipping and failing to fully open the cut-off lever.

I will continue to look for air leaks, but I think the most significant thing is that it sounds like I'm not giving it as much throttle as everyone else - I'm somewhere around 1/4 - 1/2, whereas it sounds like I need to be ~3/4 to full. Something to try.

Thanks for your help.

Andy

 

[misterg]

Just for the record, I tried it yesterday with a lot more throttle than I normally use (somewhere about 7/8 - the setting that would give me 6.5-7 knots cruising speed) and it fired up *instantly* - this is after having been stood for a week.

So, I think the correct amount of throttle was the answer, and I have been worrying over nothing /forums/images/graemlins/smile.gif

Thanks for your help.

Andy