Bukh reluctant to stop

[KenMcCulloch]

A change from the usual starting difficulties, ours intermittently fails to stop. It's been doing this for about a year, off and on. The engine is a DV36, and occasionally when the key is turned to the stop position, the revs drop back and the engine shows signs of fuel starvation but will not stop.
The stop solenoid on the DV36 operates inside the injection pump and there is no physical override so no alternative to turning the key. We have not totally ruled out an electrical problem but there is, so far as we can tell, 12v at the solenoid when the key is turned to stop. It's more or less impossible to measure that with the engine running due to the problem of access to the terminal when the engine is vibrating.
Any insights from Bukh experts will be welcome.

 

[robmcg]

Apparently, this happened to our DV36 before we owned the boat. Previous owner replaced the ignition barrel. Mind you, he broke the key in it so was replaced with some urgency. Could be worn barrel? (Caveat - in no way a Bukh expert!)

 

[sailorman]

A change from the usual starting difficulties, ours intermittently fails to stop. It's been doing this for about a year, off and on. The engine is a DV36, and occasionally when the key is turned to the stop position, the revs drop back and the engine shows signs of fuel starvation but will not stop.
The stop solenoid on the DV36 operates inside the injection pump and there is no physical override so no alternative to turning the key. We have not totally ruled out an electrical problem but there is, so far as we can tell, 12v at the solenoid when the key is turned to stop. It's more or less impossible to measure that with the engine running due to the problem of access to the terminal when the engine is vibrating.
Any insights from Bukh experts will be welcome.

well your well ahead of a Stuart Turner 8 owner, they always stopped easily

 

[awol]

Have you tried talking to/at it - always makes me sleepy. I believe there is a decompression knob - that'll kill it - or you could insert some spare part of your anatomy into the air intake. Some find that dropping a rope over the side while in gear is effective.

 

[KenMcCulloch]

Have you tried talking to/at it - always makes me sleepy. I believe there is a decompression knob - that'll kill it - or you could insert some spare part of your anatomy into the air intake. Some find that dropping a rope over the side while in gear is effective.

This is, truly, the engine that will not stop, lifting the decompressor won't stop it, even the stop control activated simultaneously with decompression it just chugs on. I will try reading to it.

 

[chewi]

This is, truly, the engine that will not stop, lifting the decompressor won't stop it, even the stop control activated simultaneously with decompression it just chugs on. I will try reading to it.

are you dropping both decompressors?
if they worl at all;, it cant run after both are dropped.

likely as not the stop solenoid is unscrewed.
talk to norman and al at bukh uk poole. they know more than we do here about bukhs.'
they won't sell you what you don't need.

 

[sailorman]

Have you tried talking to/at it - always makes me sleepy. I believe there is a decompression knob - that'll kill it - or you could insert some spare part of your anatomy into the air intake. Some find that dropping a rope over the side while in gear is effective.

Never,Ever, stop a diesel with the de-compression lever unless dire emergancy

 

[LittleSister]

Never,Ever, stop a diesel with the de-compression lever unless dire emergancy

Why not?

 

[VicMallows]

Never,Ever, stop a diesel with the de-compression lever unless dire emergancy

I, too, am awaiting the explanation? I certainly had to resort to that method when my Bukh 20 stop-solenoid burnt out (literally with smoke) and no harm came. (I have heard it suggested that a piston might hit an open valve ....... but that is ridiculous because if so it would defeat the purpose of the decompresser to facilitate starting).

Blocking the air intake on the BUKH (with the recommended handy piece of wood) does not readily work because there are two small 'bleed' vents that also need to be blocked!

 

[alan_d]

I, too, am awaiting the explanation? I certainly had to resort to that method when my Bukh 20 stop-solenoid burnt out (literally with smoke) and no harm came. (I have heard it suggested that a piston might hit an open valve ....... but that is ridiculous because if so it would defeat the purpose of the decompresser to facilitate starting).

Blocking the air intake on the BUKH (with the recommended handy piece of wood) does not readily work because there are two small 'bleed' vents that also need to be blocked!

When my Bukh 20 refused to stop with the key I was able to bring it to a halt with a gloved hand over the air intake. (I discovered later that I had dislodged the spade connector to the solenoid.)

 

[30boat]

Why not?

It puts unfair stresses on the mechanism.It works by keeping the exhaust valave open and while fine at low revs i.e starting it's not meant to work at higher revs.The whole mechanism takes a heavy beating.

 

[cliff]

The DV36 workshop manual does not show the stop solenoid however IIRC it is a similar setup as for the DV20/24. If the engine is not stopping the solenoid is not shutting off the fuel to the inlet side of the hp pump.
Slacken the four fixing screws and retighten evenly. The slightest misalignment due to tightening the four fixing screws will prevent the stop solenoid from working.

Failing that, after removing the cover plate, try slackening the lock nut on the solenoid stem and screw the solenoid in ¼ turn and lock it off (Mark the original position before starting).

 

[nigelmercier]

... try slackening the lock nut on the solenoid stem and screw the solenoid in ¼ turn and lock it off (Mark the original position before starting).

Would it be worth removing and testing that it is firing? Also check for bad connections.

As an aside, this reminded me of my mate's car in the early 1970s. He parked outside my house and walked up the drive. We chatted for a few minutes, then I noticed his car shaking rather a lot, then stop. He had the key in his hand.

 

[Twister_Ken]

Would it be worth removing and testing that it is firing? Also check for bad connections.

As an aside, this reminded me of my mate's car in the early 1970s. He parked outside my house and walked up the drive. We chatted for a few minutes, then I noticed his car shaking rather a lot, then stop. He had the key in his hand.

Had a Singer Gazelle like that. Drove at some speed over a level crossing that wasn't very level. Key fell out, car kept going.

 

[DoubleEnder]

Running on oil from the sump? It can squeeze past the rings, I think, in some circumstances. Does the exhaust smoke look different?

 

[KenMcCulloch]

Running on oil from the sump? It can squeeze past the rings, I think, in some circumstances. Does the exhaust smoke look different?

Definitely not. Compression is excellent and the oil stays remarkably clean for a long time after a change. I am inclined to pursue the suggestion of fettling the solenoid. Thanks, all, for thinking about this.

 

[345000]

When next it fails to stop on command from the panel, just run a positive feed directly from the battery to the stop solenoid - that'll tell you if it's an electrical problem.

 

[macd]

When next it fails to stop on command from the panel, just run a positive feed directly from the battery to the stop solenoid - that'll tell you if it's an electrical problem.

I imagine he might have stopped it by now...

 

[Billjratt]

Ken, it sounds as though the solenoid isn't completely strangling the supply. Before you start it next time you're down, get someone to work the key while you have your ear on the solenoid -use a screwdriver as a stethoscope - you should hear it click healthily if the electrics are OK.
I suspect Cliff has the answer (again). Something has worn and needs a wee tweek to take up the slack maybe,
As to the decompressor stop, I was led to believe it accelerated valve burn/wear.

 

[macd]

Billjrat: we last heard from the OP back in May, so I daresay he's sorted his Bukh by now. I would be a kindness if he concluded his tale, though.