dm2 slowly dies on tick over

[Leelee123poo 0]

Hi have a dm2 and recently it has started to stall on tick over after about 1/2 -1 hour of running probably when up to temp.

Its aa the governor is letting it stop and also the governor has a ticking or taping noise on tick over any ideas please

[john.k 18]

There may be just excessive backlash in the setup..................I remember the old Gardner/ Daimler  diesel buses as a kid.......the motors would slow to a near stall,and then kick up causing all the money in the coin trays to jump out.,and were set to idle so slow the body work would rattle and shake as the buses stopped for a multitude of schoolkids to troop off......Some idled around 120 rpm ,I reckon.....and I really wanted a Gardner,but the old man said they were so dear only governments could own them..... years.later on.I bought a  council  bus with bits missing,and made the replacement long governor link from a piece of bent wire. 

[john.k 18]

or ,to cut through the waffle ,you can simply speed up the idle a bit.

[RLWP 1506]

The DM2 has a rather odd set up with a link to the speed control with a spring in it. This is supposed to be free to move and have a 1/16" gap between the 'piston' and spring at idle

 

This spring/piston thing can rust up meaning it all stops working properly and the idle goes all over the shop!

 

A simple test is to take out the pin at the bottom of this piston thing and see if the idle settles down. 

 

Richard

[Tony Brooks 1626]

26 minutes ago, RLWP said:

The DM2 has a rather odd set up with a link to the speed control with a spring in it. This is supposed to be free to move and have a 1/16" gap between the 'piston' and spring at idle

 

This spring/piston thing can rust up meaning it all stops working properly and the idle goes all over the shop!

 

A simple test is to take out the pin at the bottom of this piston thing and see if the idle settles down. 

 

Richard

Sounds similar to the Lister SL4s and probably others with a light idle spring and a much heavier speed spring that is a bit loose at idle.

[RLWP 1506]

9 minutes ago, Tony Brooks said:

Sounds similar to the Lister SL4s and probably others with a light idle spring and a much heavier speed spring that is a bit loose at idle.

Yes, sort of. There's this spring that the speed control pulls, a spring onto one of the levers and a tiny spring for an idling setting/stop control. Sounds like at least one more spring than I'd like. There is also no simple idle stop to make things interesting

 

Richard

[steamraiser2 35]

One spring is for speed control the other is meant to damp the action of the other to prevent hunting at tick over. Over complicated for no good reason. I wonder if one/ both of the springs is/are stretched or of the wrong poundage always assuming that its not simply an air in fuel issue.

[john.k 18]

The reason it stalls once it gets hot is the hot fuel is thinner,and the effect of wear in the fuel metering setup in the pumping units is more pronounced..........the explanation being wear and leakage paths......consult any book on diesel engineering for a picture of a worn plunger and barrel.

[RLWP 1506]

21 hours ago, steamraiser2 said:

One spring is for speed control the other is meant to damp the action of the other to prevent hunting at tick over. Over complicated for no good reason. I wonder if one/ both of the springs is/are stretched or of the wrong poundage always assuming that its not simply an air in fuel issue.

As I said, one I worked on recently was behaving very strangely because the piston/spring thing was rusty. Instead of a simple set up it was acting as a weird spring/damper thing. When cleaned up the idle went back to a nice steady thump-thump-thump

 

Richard

[BWM 243]

Could this cause other running problems? I've been chasing a defect on the RN in my sons boat which dying out at low revs is one symptom, along with power loss/misfiring at higher rpm under load.

 Has anyone a picture of the governor, complete with springs that i can compare with his?

[RLWP 1506]

6 minutes ago, BWM said:

Could this cause other running problems? I've been chasing a defect on the RN in my sons boat which dying out at low revs is one symptom, along with power loss/misfiring at higher rpm under load.

 Has anyone a picture of the governor, complete with springs that i can compare with his?

If I remember, I'll take a picture on Monday. There's a diagram in the manual too

 

Richard

[BWM 243]

1 hour ago, RLWP said:

If I remember, I'll take a picture on Monday. There's a diagram in the manual too

 

Richard

Thanks Richard 

[john.k 18]

Sounds typical of fuel starvation....blocked filters ,kinked pipes ,flakes of rust ,or flakes of paint blocking  the tank pickup..my favorite was a small square of nylon shirt material,about 1 1/2 " a side.......... it would stick to the tank completely invisible when the tank was empty ,fill the tank and the rag was floating round just waiting to block the fuel intake,stop the motor,and it would float off .  drained ,removed and replaced  the tank  to find the problem.............and the boat owner wanted to transfer the old fuel into the new tank.

[RLWP 1506]

On 19/07/2019 at 14:43, BWM said:

Thanks Richard 

 

This tube thing links the speed control to the engine. The rod has a piston on the end, a spring sits on top of that and bears against the brass adjuster at the top. Lifting the rod pulls the whole thing upwards via the spring. At idle, the spring is supposed to be fully unloaded and loose

 

That link sits on a lever on the side of the governor housing, directly connected to the rack by the lower arm. There is a second spring pulling the lever against the governor

 

 

The governor lever links directly to the rack of the pump

 

This device also contains a spring, presumably to control the idle. Or let the rack move across against this stop to cut the fuel

 

Does that help? It was corrosion in the tubular thing that was causing trouble, together with the speed control on the roof having no positive idle position

 

Richard

[rustynewbery 16]

The spring on the governor is only designed to fix the rpm at around 400 and is a throwback to when RN's were stationary machines running usually around 1000 RPM. It should not be attached as shown when the engine has warmed up to 60deg.

 

If the rack is dirty, undo the cover and spray with WD40 while moving it manually, that should clean it up well.

 

If there's any play in the governor arm hole, the anti stall device will have no effect and - it will stall! Disconnecting the linkage will show if it is contributing to the symptoms or not.

The nut on the end of the anti stall device can be used to adjust its correct operation; you should hear it "ticking" as it works. So this is correct in your case

 

Inside the governor housing are a pair of phosphor bronze weights mounted horizontally which does defy the logic behind governors which are usually vertical.  Any clanking noise from these is caused by the weights dropping due to gravity and when cold, it can sound quite alarming.  Use the oil hole by slackening the screw and inserting a good old squirt or more of the engine oil in use [SAE30 or XHD30 typically]

 

While idle speeds of 100-200 RPM can be achieved, remember that the engine was never designed to do this and more so, rocking the boat from side to side will speed up or slow down the idle, thus creating the condition for a stall

 

Just one more thing, £12 a year will give you membership of the RN Register if you're not.  www.rnregister.org.uk

 

[billybobbooth 63]

I was more worried about the kink in what looks like a fuel pipe just under the governer

[billybobbooth 63]

The last pic this should be adjusted so when fully back it (no fuel) it should have just touched from what I understand and how mine is done as if it's not adjusted correctly it can cause pressure inside the pump on the brass parts and damage them.

 

Best way to test if its fuel piping is remove the pipe into the injector pump and put a  container with a hole at the bottom and pipe strait into the pump, and fill with diesel it could be a faulty lift pump.