difficult cold start despite recon

chewi

chewi

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I have a bukh dv10me of 1980 vintage.

I have this winter treated it to a professional recon, but it's still sluggish to start from cold.
Once started its fine. and restarts instantly, even after overnight cooling, just as it did before the recon, but is sluggush again aweek later.

I use no throttle to start.
Tank is above filter has been bled.
Lift pump is supposedly good(pumps fuel while bleeding)
There are no preheaters/glopug etc in the design.
New fuel filter
clean fuel


Recon included injector service, wet liner remove/refit, new exhaust seat, new rings, shells, head gasket.
wet liner was deemed good to refit, as was piston.

Have I got an installation problem
Have I reconned a dead engine?
Am I optimistic in expecting it to instantly fire?
Should I use throttle?
why does it restart easily at T+24hrs but not T+7days?


Any ideas?
 
Last edited:
chewi said:
I have a bukh dv10me of 1980 vintage.

I have this winter treated it to a professional recon, but it's still sluggish to start from cold.
Once started its fine. and restarts instantly, even after overnight cooling, just as it did before the recon, but is sluggush again aweek later.

I use no throttle to start.
Tank is above filter has been bled.
Lift pump is supposedly good(pumps fuel while bleeding)
There are no preheaters/glopug etc in the design.
New fuel filter
clean fuel


Recon included injector service, wet liner remove/refit, new exhaust seat, new rings, shells, head gasket.
wet liner was deemed good to refit, as was piston.

Have I got an installation problem
Have I reconned a dead engine?
Am I optimistic in expecting it to instantly fire?
Should I use throttle?
why does it restart easily at T=24hrs but not T+7days?


Any ideas?
Click to expand...


Maybe a little ovality in the bore of the liner... not matching the perfectly circular new rings and leading to less than ideal compression.

After 24 hours maybe still enough oil around to give sufficient compression for a quick start but gone after a week .

Any chance that the battery is not in its prime or that there is some resistance in the battery lead or earth lead connections resulting in a slowish cranking speed?

Have you tried some throttle when starting it? Full throttle even.
 
Vics, thanks for swit feedback at stupid o'clock!

batteries are good, cranking speed is good,
have not tried throttle yet, but key is in cabin while throttle is in cockpit, so I hoped to avert that, but if a bit of throttle is all it takes though I'll be OK with that!#

btw tickover is adjusted to 1000rpm which feels right.
If it's ovality might it improve as the new rings settle?
 
chewi said:
Vics, thanks for swit feedback at stupid o'clock!

batteries are good, cranking speed is good,
have not tried throttle yet, but key is in cabin while throttle is in cockpit, so I hoped to avert that, but if a bit of throttle is all it takes though I'll be OK with that!#

btw tickover is adjusted to 1000rpm which feels right.
If it's ovality might it improve as the new rings settle?
Click to expand...

Hopefully

Idle speed according to the owners manual should be 900 to 1200 rpm

The old Volvo needed a good bit of throttle . I was also thinking I've had two diesel cars. The starting instructions for one was to press the accelerator .. the current one has a device that automatically opens the throttle a bit if the engine is cold.

If you use much throttle you need to be able to close it again as soon as the engine fires. You don't want to let it rev high when still cold
 
I fitted a pre heater in my Dv20.
Starts very well even after being left a couple of weeks in the cold weather.
I use about one third throttle.
 
catalina1 said:
I fitted a pre heater in my Dv20.
Starts very well even after being left a couple of weeks in the cold weather.
I use about one third throttle.
Click to expand...

That's what I used to do with my old (unreconned) 1982 DV20. I think the pre-heater helps.

Re knocking back the revs after the engine's started, I used to use the boathook from the companionway to push the Morse lever back to vertical.
 
Do some of the older engines (volvos) have a throttle sequence to ensure the fuel pump gives more fuel when cold? Could this be the same on the bukh. Also had a problem where the egine would not start straight away after being left some time but it was more the 2-3 week, but turned out the return line needed a valve put in to keep some pressure in the return line, a check valve?

Shouldn't the people who rebuilt it for you be offering some follow up service?

How frustrating and good luck with it.
 
stav said:
Do some of the older engines (volvos) have a throttle sequence to ensure the fuel pump gives more fuel when cold? Could this be the same on the bukh. Also had a problem where the egine would not start straight away after being left some time but it was more the 2-3 week, but turned out the return line needed a valve put in to keep some pressure in the return line, a check valve?

Shouldn't the people who rebuilt it for you be offering some follow up service?

How frustrating and good luck with it.
Click to expand...

As yet I have not approached them, as the symptoms are much the same as pre the recon, and I've only had the boat launched 2 weeks ago. I would like to take the collective wisdom of the forum with me before I go there.

I had wondered about fuel starvation, but even the bottom of the tank is above the engine, so I don't understand how a valve would help? Surely once bled and run long for any reasonable period it will have fuel, unless my tickover starting is starving it of fuel, but if that were true wouldn't also be sluggish at T+24hrs?

Maybe theres a combination with no latent oil on the bore at cold (as VicS said) AND too little fuel at tickover.
 
The best place to start with old diesels is a compression test, if you have good compression then it’s likely to be fuel related as other have said fitting a pre-heater can work wonders for the starting reliability of older engines.

re the compression test you can't use the DIY testers that you get from Halfords and such like so it's probably best to ask the firm that did the rebuild if they could do one for you.
 
I don't know about Bukhs but my 1987 VP 2002 needs full or nearly full throttle plus operating the cold start control for the first start of the day. It behaves perfectly - good fuel economy and no oil consumption so I think that that's how it's meant to be. As soon as it starts I reduce the throttle to give about 1500 rpm. and then progressively lower over the course of 2-3 minutes.
 
chewi said:
Once started its fine. and restarts instantly, even after overnight cooling, just as it did before the recon, but is sluggush again a week later

....

Any ideas?
Click to expand...

Similar symptoms on our Yanmar 2gm20 turned out to be small leaks in the fuel system which presumably allowed air to bleed back in on standing. Different engine, I know, and the tank was below the engine, but food for thought, maybe?

The cure was to eliminate even the smallest weeps from diesel pipes (and the fuel filter bowl, which I think was the main culprit). Weeps were detected by thoroughly cleaning everything, then using a piece of coloured paper towel to wipe every joint - if it turned dark, there was a leak.

Just a suggestion.

Andy
 
How did the reconditioning engineer decide the liner was OK to refit? Did he do a compression test as part of the recon?
I think it would be worthwhile lifting the phone to find out.
Otherwise you will probably want a compression test after lying idle for a week and also a day to see if there is a significant difference.
Or maybe just plaster over the cracks and fit a coldstart device?
 
Another vote for some throttle, being new to diesel's it wasn't until the engineer told me this that we started using 1/3 throttle and it sorted us.

Out of interest, is it better starting cold on a warm day? I'm just wondering because if it is then you can maybe eliminate fuel as an issue - i.e. it's a compression issue, if it was equally bad starting cold on a warm day then it's more likely fuel?
 
The Lazy Kipper said:
Another vote for some throttle, being new to diesel's it wasn't until the engineer told me this that we started using 1/3 throttle and it sorted us.

Out of interest, is it better starting cold on a warm day? I'm just wondering because if it is then you can maybe eliminate fuel as an issue - i.e. it's a compression issue, if it was equally bad starting cold on a warm day then it's more likely fuel?
Click to expand...

Engineers that did the recon are Bukh approved, come well recommended and I did not pinch them on parts, so if it needed a liner it would have had one, I believe he cleaned it and was convinced it did not need a new one.

I am leaning to believe its fuel starvation at tickover, it may get enough to run but not to start, so I will try with throttle. I think the high tank precludes leakage being cause of that, I think a leak would only mess the bilge up.

I've only had 1 weekend in water since the recon to try it so far, and once started its end of diagnosis, so I will try throttle next time, hopefully this pm If I get my dayjob work done this am.

Thankyou all.
 
Do some of the older engines (volvos) have a throttle sequence to ensure the fuel pump gives more fuel when cold? Could this be the same on the bukh.
Click to expand...

Pulling and returning the stop mechanism I think is what you refer to on the VP 2001 series. Even older ones eg MD11) had a button to press on the injector pump
There is no mention of anything like either of these in the owners manual.

However, one manual I have downloaded indicates the existence of a rubber plug on the air inlet, removal of which allow a small quantity of oil to be injected.
Another describes an optional "Thermostart" device operated by a keyswitch position between the normal running position and the cranking position. (What Babylon describes as a preheater I guess)
These are intended as aids for starting in cold conditions.

Misterg mentions small leaks in the fuel system.
Similar symptoms on our Yanmar 2gm20 turned out to be small leaks in the fuel system which presumably allowed air to bleed back in on standing. Different engine, I know, and the tank was below the engine, but food for thought, maybe?
Click to expand...
This is another possibily. The leaks may be so small as to not be evident as fuel leaks but they allow air to enter slowly while standing and the fuel to drain back.
Spinning while decompressed might re-prime the fuel system.
 
What you describe seems to be pretty much standard for diesels without pre-heat.
Certainly my Yanmar 1GM behaves just as you describe.
Standard procedure is to use more "throttle", ie move speed control lever forward, in cold weather, and return to tick-over once engine starts to run. Engine a bit smoky at first but OK once it's run for a short while.
Can be a right *! in really cold weather.
If it's been running relatively recently, or in warm weather, no problem.

(ETA: there's another thread on cold starting, mainly having to do with pre-heat so not entirely relevant here, but shows that you are not alone!)
 
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pampas said:
How would you start a diesel car, ?
Click to expand...

My diesels have had a automatic preheat relay and throttle advance.

Just for interest the Thornycroft handbook for my engine suggests 30 seconds preheat and full throttle, but almost always it will do with much less and if being used every few days doesnt need any heat or throttle.
 
pampas said:
How would you start a diesel car, ?
Click to expand...

With no problem at all, in any weather. My first one had preheat. My current one (MINI Cooper D) has a computer and, I assume, preheat; and is a touch more sophisticated than the Yanmar. Seems that boat engines are, in their state of development, at least 50 years behind car engines.
 
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