BMC 1500 running rough on start up

[Cheshire cat]

I'm going with the low compression theory at the moment. I'm fairly confident it's the cylinder at the other end of the block that has a problem. Hopefully, more news on Wednesday unless the weather is terrible.

[StephenA]

32 minutes ago, Cheshire cat said:

I'm going with the low compression theory at the moment. I'm fairly confident it's the cylinder at the other end of the block that has a problem. Hopefully, more news on Wednesday unless the weather is terrible.

 

Its odd that it goes away as things warm up but comes back so soon after a restart - even if for a smaller length of time. Compression or a sticky valve?

 

Does it make any odd noises? Does the exhaust note change when the 4th cylinder kicks in ?

Edited August 14, 2023 by StephenA

[Cheshire cat]

11 hours ago, StephenA said:

 

Its odd that it goes away as things warm up but comes back so soon after a restart - even if for a smaller length of time. Compression or a sticky valve?

 

Does it make any odd noises? Does the exhaust note change when the 4th cylinder kicks in ?

 

I'm trying to rationalise that in my mind. Possibly unburnt fuel is helping out the piston rings? Takes a while to build up on a cold start but already "wet" on restart? Maybe.

 

Can also see that it could be a sticky valve. It stops sticking once it's got a bit of lube from unburnt fuel?

 

I would say that there aren't any odd noises in so much as there's no clacking going on. The exhaust note changes when the fourth cylinder kicks in. I'll see if I can get something loaded on Youtube. 

Cold start. Engine picks up after 57 seconds

[Tony Brooks]

41 minutes ago, Cheshire cat said:

 

I'm trying to rationalise that in my mind. Possibly unburnt fuel is helping out the piston rings? Takes a while to build up on a cold start but already "wet" on restart? Maybe.

 

Can also see that it could be a sticky valve. It stops sticking once it's got a bit of lube from unburnt fuel?

 

I would say that there aren't any odd noises in so much as there's no clacking going on. The exhaust note changes when the fourth cylinder kicks in. I'll see if I can get something loaded on Youtube. 

Cold start. Engine picks up after 57 seconds

 

It seems to have very bad diesel knock on what sounds like one cylinder until the fourth cuts in. That suggests poor atomisation on one cylinder.

 

I would check the valve clearances cold to make sure there is some, and then take the injectors out to inspect the top hast etc. It has been known for a wrong injector to snap the end out f the top hat, That lowers the compression on that one cylinder. I would also check the spray pattern by reversing them on the pipe, one at a time, and spinning the engine. For goodness’s sake, stay very well clear of the spray and no speaks/naked flames while doing this.

 

I agree, no undue clanking noises, just the loud knock.

[john.k]

If a cylinder is missing from low comp or a dud glow plug,there will be  white smoke and a kerosine smell to the exhaust .........if there is no fuel to the cylinder ,there will be no smoke............simplest way to check this is to crack each fuel union in series with the motor running .......incidentally,if you just crack the union,and froth comes out ,then for sure there is an air leak somewhere ...........(its also possible to completely block off a fuel pipe by overtightening the nut.)

[Tracy D'arth]

If the 4th injector has the wrong spray pattern because it is a foreigner that will be the problem.  BMC injectors are totally different on the nozzles for a good reason.

[Bee]

Put the spanners away (except for a couple to get that injector out) As Tracy D.Arth says that odd injector is almost certainly the problem.

[Cheshire cat]

This thread has been running too long. I posted earlier that I had been in touch with the owner. He has had this problem for some time and had the injectors replaced with this "set" about two months ago. The problem went away for a short while but has returned. There is grey smoke from the exhaust until the fourth cylinder joins in. 

 

My plan is 

1) turn the engine over manually to see if I can detect low compression on one of the cylinders. I haven't got a diesel compression tester. 

2) Have a look at the rockers to see what state they are in. If they are worn that might be an indicator as to the likely state of the valves and guides.

3) Set the gaps on the valves to 15 thou

4) Start the engine and see what happens

 

If it still starts on three I shall turn my attention to the injectors. Warning duly noted about making sure I don't inject myself with diesel. 

 

What does a top hat look like? Should it come out of the injector hole?

[Tracy D'arth]

Top Hat  is the heat shield which surrounds the end of the injector.  Can be VERY difficult to remove but some come out with the injector.

[Tony Brooks]

3 hours ago, Cheshire cat said:

This thread has been running too long. I posted earlier that I had been in touch with the owner. He has had this problem for some time and had the injectors replaced with this "set" about two months ago. The problem went away for a short while but has returned. There is grey smoke from the exhaust until the fourth cylinder joins in. 

 

My plan is 

1) turn the engine over manually to see if I can detect low compression on one of the cylinders. I haven't got a diesel compression tester. 

2) Have a look at the rockers to see what state they are in. If they are worn that might be an indicator as to the likely state of the valves and guides.

3) Set the gaps on the valves to 15 thou

4) Start the engine and see what happens

 

If it still starts on three I shall turn my attention to the injectors. Warning duly noted about making sure I don't inject myself with diesel. 

 

What does a top hat look like? Should it come out of the injector hole?

 

Exactly as Tracy describes, except it drops down the hole crown first. The brim sites on a land around the hole that sits on a copper washer.

 

There should be a little crinkly steel heat shield washer sitting between the injector nozzle and the bottom of the top hat.

 

Another copper washer goes around the injector nozzle and sits on the brim of the top hat.

 

If when you look down the hole you can see a small (say roughly 5mm) hole, then the top has is intact. If you see a larger hole (say about 1/2") then the top hat is either missing or the top has snapped off.

[Cheshire cat]

Interesting day. I decided to buy a couple of injectors. Hopefukky replace the dodgy one and have a spare.

 

Called in to a diesel centre in Leamington that advertises them on Ebay. He had some but would only sell on an exchange basis. Fair enough. Went to Calcutt and they sorted me out.

 

Back at the boat. 

Turned the engine over with difficulty. Couldn't use the breaker bar because it was too long and the socket wrench was a bit too small which caused jerky movements. Result inconclusive.

 

Took the tappet cover off. Noticed that one of the cylinder head bolts holding the rocker pedestals down had blue engine paint on it. It must have been external at some point. Makes me think that someone has had the cylinder head off in the past. Took the rocker assembly off. The rocker faces are worn, some worse than others, but no great indentations. Some valve tops showing slight signs of wear.

Checked the valve clearances. Some were only 12 thou but no real surprises.

 

Decided not to start the engine because I hadn't done anything that would make a difference.

 

Took out number one injector easily. Turned out it isn't a rogue. The inbound pipe has been swaged badly which means the locking nut won't go up the threads as far as it does on the other pipes. I noticed that the pin hole referred to by Tony was buried under a coating of carbon. Replaced by a rebuilt injector. (The replaced injector has been in service for less than 150 hours.

 

Took out number two or at least tried to. It put up a fight. In the end I levered it out which caused me to loose the spill rail bolt in to the engine tray. An hour later I was having a serious sense of humour failure, eventually managed to recover it by dragging a rag lengthways through the tray.

 

Number two injector didn't have the large copper washer fitted! I'm not sure of the ramifications of this. Presumably it would be difficult to get a good seal around the injector. Picture attached of the nozzle on this injector. I presume the black crescent is where it has been touching the fireshield washer.

 

I didn't have my laptop with me so couldn't work out where the fireshield washers went. The old ones are still in there. New ones not used. 

 

Managed to put everything back together and fired up the engine. It started on four! Stopped and started again several times and it always came back on four and the rev counter showed 800 rpm. Very pleased. There's still what Tony called a diesel knock present though and there's more black smoke than I think there should be.

 

By this time it was 6.30 so I didn't do anything with regards to investigating further.

 

 

 

 

 

On 10/08/2023 at 16:00, Eeyore said:

You could try holding the key in the heat position for 30 seconds or so after the engine has started. This is of course a fully automatic feature on most modern diesel engines. It reduced the initial smoking and settled the idle to something approaching smooth at lot quicker.

The fault on mine (long gone) was a restriction in the spill line, causing overfueling and carbon blockage of the exhaust ports. But curiously similar symptoms (including the black smoke).

 

I'm interested in the last two lines. What do you think about this. It's the spill line on its way back to the fuel flter

[StephenA]

1 hour ago, Cheshire cat said:

Interesting day. I decided to buy a couple of injectors. Hopefukky replace the dodgy one and have a spare.

 

Called in to a diesel centre in Leamington that advertises them on Ebay. He had some but would only sell on an exchange basis. Fair enough. Went to Calcutt and they sorted me out.

 

Back at the boat. 

Turned the engine over with difficulty. Couldn't use the breaker bar because it was too long and the socket wrench was a bit too small which caused jerky movements. Result inconclusive.

 

Took the tappet cover off. Noticed that one of the cylinder head bolts holding the rocker pedestals down had blue engine paint on it. It must have been external at some point. Makes me think that someone has had the cylinder head off in the past. Took the rocker assembly off. The rocker faces are worn, some worse than others, but no great indentations. Some valve tops showing slight signs of wear.

Checked the valve clearances. Some were only 12 thou but no real surprises.

 

Decided not to start the engine because I hadn't done anything that would make a difference.

 

Took out number one injector easily. Turned out it isn't a rogue. The inbound pipe has been swaged badly which means the locking nut won't go up the threads as far as it does on the other pipes. I noticed that the pin hole referred to by Tony was buried under a coating of carbon. Replaced by a rebuilt injector. (The replaced injector has been in service for less than 150 hours.

 

Took out number two or at least tried to. It put up a fight. In the end I levered it out which caused me to loose the spill rail bolt in to the engine tray. An hour later I was having a serious sense of humour failure, eventually managed to recover it by dragging a rag lengthways through the tray.

 

Number two injector didn't have the large copper washer fitted! I'm not sure of the ramifications of this. Presumably it would be difficult to get a good seal around the injector. Picture attached of the nozzle on this injector. I presume the black crescent is where it has been touching the fireshield washer.

 

I didn't have my laptop with me so couldn't work out where the fireshield washers went. The old ones are still in there. New ones not used. 

 

Managed to put everything back together and fired up the engine. It started on four! Stopped and started again several times and it always came back on four and the rev counter showed 800 rpm. Very pleased. There's still what Tony called a diesel knock present though and there's more black smoke than I think there should be.

 

By this time it was 6.30 so I didn't do anything with regards to investigating further.

 

 

 

 

 

 

I'm interested in the last two lines. What do you think about this. It's the spill line on its way back to the fuel flter

 

That doesn't look good - I'd get a new spill rail as they're not that expensive.

[Eeyore]

1 hour ago, Cheshire cat said:

 

 

I'm interested in the last two lines. What do you think about this. It's the spill line on its way back to the fuel flter

You might want to drop the exhaust manifold off, easy enough; you could just about fit a pencil through the carbon on mine!

Edited August 17, 2023 by Eeyore

[Tony Brooks]

1. The injector photo. The carbon crescent suggest to me that the fire shield washer is distorted. Ideally, I would like to replace at least that one. They just drop down the hole, so they sit on the inside of the crown of the top hat. If it is running OK I am not sure it is worth doing this though. Actually probably not touching the fire shield washer.

 

2. The leak off pipe. The "bulge" that seems to concern you looks to me like a blob of silver solder that a less than exert solderer used to solder the banjo union onto the leak off pipe. I see no reason to worry about it unless it is leaking.

 

3. No large washer under the injector has the potential to allow a compression leak because you are then relying on the fire shield washer to make a seal. As they are steel and the one in use has already been squashed a bit, probably not ideal.

 

4. Not sure what you mean by the "pin hole", if you mean the auxiliary spray hole they are minuscule and the carbon would easily hide it. It is so small I used to need a magnifying glass to see it, nowadays I doubt I could see it.

 

5. All diesels produce diesel knock, it is normal, when that engine is running on for it sounds normal to me.

 

Thanks for the detailed feed back.

[Cheshire cat]

Tony,

I was given new steel fire shield washers with the injectors but didn't have an exploded parts diagram. Looking down the injector hole I thought I was looking at the base of the top hat. 

 

The pin hole is what you are calling the auxilliary spray hole. What is its purpose. 

 

Regarding the spill rail, I was referring to the poorly made bend which looks severe enough to put a restriction on diesel returning to the filter. Is the diesel under pressure at this point in its journey. I'm wondering if the bend could be improved with a bit of heat. 

 

New spill rails are available from Calcutt. £55.00

 

Eeyore, what is involved in cleaning out the exhaust manifold. Is it easy to take off? No point in doing that though unless we work out what is causing the excessive carbon to be created in the first place.

 

I'd just like to say thankyou again for everyone's help. 

[Tony Brooks]

53 minutes ago, Cheshire cat said:

Tony,

I was given new steel fire shield washers with the injectors but didn't have an exploded parts diagram. Looking down the injector hole I thought I was looking at the base of the top hat. 

 

The pin hole is what you are calling the auxilliary spray hole. What is its purpose. 

 

Regarding the spill rail, I was referring to the poorly made bend which looks severe enough to put a restriction on diesel returning to the filter. Is the diesel under pressure at this point in its journey. I'm wondering if the bend could be improved with a bit of heat. 

 

New spill rails are available from Calcutt. £55.00

 

Eeyore, what is involved in cleaning out the exhaust manifold. Is it easy to take off? No point in doing that though unless we work out what is causing the excessive carbon to be created in the first place.

 

I'd just like to say thankyou again for everyone's help. 

 

Normally the leak off from the injectors flow should be almost nothing unless they are worn, so as long as the return to the tank is on the other side of that banjo (as is typical) I would not worry about the bend. I had a 1/16" bore pipe on the leak off on the Bukh and there was no problem.

 

The auxiliary spray hole more or less only works when the injector needle is not pushed fully upwards, and that is during cranking. It directs a spray of fuel onto/into the hottest part of the pre-combustion chamber as an aid to cold starting.

 

Without seeing for myself and possibly prodding about with a thin screwdriver, I would not like to say what you were looking at. The heat shields have a raised crimp around the middle, and you can often see the vestiges of this on the old ones.

 

 

 

To add. If a Perkins nozzle is fitted, not only is it too long, so it can push the bottom off the top hat, the aux. spray hole is likely to be in the wrong place.

[Eeyore]

4 hours ago, Cheshire cat said:

 

Regarding the spill rail, I was referring to the poorly made bend which looks severe enough to put a restriction on diesel returning to the filter. Is the diesel under pressure at this point in its journey. I'm wondering if the bend could be improved with a bit of heat. 

 

New spill rails are available from Calcutt. £55.00

 

Eeyore, what is involved in cleaning out the exhaust manifold. Is it easy to take off? No point in doing that though unless we work out what is causing the excessive carbon to be created in the first place.

 

I'd just like to say thankyou again for everyone's help. 

Under normal conditions the (spill) fuel used to cool and lubricate the moving parts of the injection system returns to the tank (or recirculates) under very little pressure. However a blockage in the spill system can result in very high pressure build up, and all manner of strange behaviour.

Fit a new the new spill rail first and see how it goes.

The carbon build up on mine almost filled the exhaust ports on the head (extending into the manifold) leaving only a very small hole for the exhaust gases.

I decided that having the head off was the easiest course of action, hopefully it won't come to that for you. 

[Cheshire cat]

Thanks Eeyore. I don't particularly want to get involved in taking the head off at the moment. We might have to consider it if the fault returns.

My track record with exhaust manifold stoods isn't good. I really don't want to be getting into trying to remove snapped exhaust studs.  

 

The boat is going out for a cruise at the Bank Holiday. It will be interesting to see how it performs.

[David Mack]

9 hours ago, Cheshire cat said:

Regarding the spill rail, I was referring to the poorly made bend which looks severe enough to put a restriction on diesel returning to the filter. Is the diesel under pressure at this point in its journey. I'm wondering if the bend could be improved with a bit of heat. 

The spill rail is not under much pressure. Can

You not just remove the spill rail and see if you can blow through it past that bend? If you can then the distortion is not going to be causing any problems.

[Cheshire cat]

That's a good idea David. We'll try that before spending any money.

[Tony Brooks]

1 hour ago, Cheshire cat said:

That's a good idea David. We'll try that before spending any money.

 If you get it off you could try tapping down on the kink with a hammer, that might open it up a little

[StephenA]

Sooo........ any updates?

[Cheshire cat]

The engine has been behaving itself although it has only been out for two short runs. 

 

In my own mind if the fault reappears I would want to look at the spill rail and also try to borrow a diesel compression tester. 

[Tracy D'arth]

27 minutes ago, Cheshire cat said:

The engine has been behaving itself although it has only been out for two short runs. 

 

In my own mind if the fault reappears I would want to look at the spill rail and also try to borrow a diesel compression tester. 

I think it is sorted now. That spill rail won't be completely closed, the return flow is very small on these BMC engines, I have seen them with no spill rail fitted and they don't throw much fuel out.

Give it a good work out if you can find somewhere well banked with concrete or a river, diesels love being thrashed.