BMC 1500 Diesel Overreving

[jacksonp_uk]

Hi all you engine experts out there.

 

I have recently bought a narrowboat with a 1500 BMC Diesel engine.

 

It has started showing a tendency to overrev quite drasticaly for no apparent reason. When left at say 1500 rpm on a fixed throttle setting the revs will suddenly start to build and then become totally unreponsive to throttle adjustments. Only a shut down will prevent a meltdown. When restarted the engine will then appear to be OK again.

 

Any suggestions at what I should be looking for, checking?

 

Paul Jackson

[Sir Nibble]

It's not funny when diesels do this, ever heard a Gardner hit 5000rpm?

Most likely cause is lubricating oil getting into the intake. Do you have an oil bath air filter? are you sure your sump is not overfilled?

[magnetman]

It's not funny when diesels do this, ever heard a Gardner hit 5000rpm?

Most likely cause is lubricating oil getting into the intake. Do you have an oil bath air filter? are you sure your sump is not overfilled?

 

I've done this, properly, well and truly, with a Lister SR2. Completely wiped out the area with smoke. Engine wouldn't stop, burning its own diluted sump oil which was breaching the rings. Luckily the decompressors were fitted still so I got it stopped quite quickly...

Listers are bad like this because of their protected fuel system, weatherproof but it does make the fuel leaks end up in the sump.

 

Edit. It sounds like this BMC does stop if fuel is cut off so it isn't running away by the look of it.

 

edit 2. Sorry this edit clashed with the next post.

Edited January 29, 2007 by magnetman

[John Orentas]

What is the general condition of the engine on a scale of 1 - 10.

1 = New ............... 10 = knackered.

 

How do you manage to stop the engine when it does this.

[jacksonp_uk]

What is the general condition of the engine on a scale of 1 - 10.

1 = New ............... 10 = knackered.

 

How do you manage to stop the engine when it does this.

 

hi

 

The engine is probably about 7 to 9 on your scale. It has suffered by being maintained by the mechanic from hell as I am slowly discovering.

 

The engine is stopped by the standard pull stop on the injector control.

 

PJ

[nigel carton]

Hi, I had a similar problem with mine and found the throttle linkage on the injector pump, the quadrant what ever you want to call it moving slightly on its own, may be worth having a look at it when the engine is running.

 

Nigel

[John Orentas]

hi

The engine is probably about 7 to 9 on your scale. It has suffered by being maintained by the mechanic from hell as I am slowly discovering.

The engine is stopped by the standard pull stop on the injector control.

 

PJ

 

 

Hi Paul.

 

In view of the fact that you can stop the engine in that way we may have to modify our views, looking more like a pump problem. As a first step it may be an idea to do an oil change, err to the heavier grades. Let's see what the others say.

Edited January 29, 2007 by John Orentas

[Theo]

Hi, I had a similar problem with mine and found the throttle linkage on the injector pump, the quadrant what ever you want to call it moving slightly on its own, may be worth having a look at it when the engine is running.

 

Nigel

 

 

Could it be a governor problem?

 

Nick

[Yamanx]

There is an adjustment on the pump that needs to be set whilst on a test rig by a diesel pump setter-uper. If you or the mechanic you mention have adjusted this by mistake (Usually its mistaken for the bleed screw), it can cause the over revving you describe. The best course of action is to remove the injection pump and take it to a diesel pump specialist, R&D Diesel for instance.

[jacksonp_uk]

There is an adjustment on the pump that needs to be set whilst on a test rig by a diesel pump setter-uper. If you or the mechanic you mention have adjusted this by mistake (Usually its mistaken for the bleed screw), it can cause the over revving you describe. The best course of action is to remove the injection pump and take it to a diesel pump specialist, R&D Diesel for instance.

 

Thanks I think this may well be the best course of action in the end

 

PJ

[Guest]

My Yanmar used to run away in this fashion. It was a mladjusted governor. Set up as per the book it was an instant cure.

[Tony Brooks]

Hi all you engine experts out there.

 

I have recently bought a narrowboat with a 1500 BMC Diesel engine.

 

It has started showing a tendency to overrev quite drasticaly for no apparent reason. When left at say 1500 rpm on a fixed throttle setting the revs will suddenly start to build and then become totally unreponsive to throttle adjustments. Only a shut down will prevent a meltdown. When restarted the engine will then appear to be OK again.

 

Any suggestions at what I should be looking for, checking?

 

Paul Jackson

 

 

This engine uses a hydraulic governor and it will give all sorts of odd speed related problems if the fuel pressure goes awry.

 

1. Clean and change all water traps (including well hidden ones and the one in the top of the lift pump and filters.

 

2. Check the whole,fuel; system for secure and tight joints - air can cause this.

 

3. Check the non-return valve in the filter head is clean and free to move (Extra hexagon screwed into filter head by an IN arrow symbol.

 

4. Ensure tank breather is clear and free.

 

5 Feed engine from a can connected straight to the lift pump. If this cures the fault the pick up in the tank is probably blocked.

 

6. feed from a high level can directly into the engine filter. If this cures the fault the lift pump might be faulty - there is no logic to this one, but it has been known. And it did not reproduce the fault when the "faulty" pump was tried on another engine.

 

Try enthusiastically tapping the governor housing with the engine revving and throttle closed. They have been know to jamb - especially if water has got through the filter system. The governor is located between the throttle and stop lever on the injector pump.

 

 

Hope this helps

 

Tony Brooks

[David Schweizer]

1. Clean and change all water traps (including well hidden ones and the one in the top of the lift pump and filters.

I have never understood why the maintenance manual tells me to clean the lift pump filter everY 200 hours. I never ever cleanded them on a car and I have never cleaned one on my boat engine. When the lift pump was removed during the recent engine re-build, we opened the top a to inspect the filter - it was completely clean. !!!

[Tony Brooks]

I have never understood why the maintenance manual tells me to clean the lift pump filter everY 200 hours. I never ever cleanded them on a car and I have never cleaned one on my boat engine. When the lift pump was removed during the recent engine re-build, we opened the top a to inspect the filter - it was completely clean. !!!

 

 

And so it should be if you have adequate pre-treatment and look after the fuel, but that is not the norm on older boats.

 

Trouble is if you do not do it, you will not know when there is a problem until the engine plays up.

 

It is also one of ther first places to find sign of water or diesel bug.

 

Tony Brooks

[jacksonp_uk]

This engine uses a hydraulic governor and it will give all sorts of odd speed related problems if the fuel pressure goes awry.

 

1. Clean and change all water traps (including well hidden ones and the one in the top of the lift pump and filters.

 

2. Check the whole,fuel; system for secure and tight joints - air can cause this.

 

3. Check the non-return valve in the filter head is clean and free to move (Extra hexagon screwed into filter head by an IN arrow symbol.

 

4. Ensure tank breather is clear and free.

 

5 Feed engine from a can connected straight to the lift pump. If this cures the fault the pick up in the tank is probably blocked.

 

6. feed from a high level can directly into the engine filter. If this cures the fault the lift pump might be faulty - there is no logic to this one, but it has been known. And it did not reproduce the fault when the "faulty" pump was tried on another engine.

 

Try enthusiastically tapping the governor housing with the engine revving and throttle closed. They have been know to jamb - especially if water has got through the filter system. The governor is located between the throttle and stop lever on the injector pump.

Hope this helps

 

Tony Brooks

 

Hi Tony

 

Thanks for advice. After further experimentation I think the govenor valve may well be jamming abd the most likely cause of my grief. Do these things wear. If so which bits should be renewed? Or do you just strip and clean it all out?

 

thanks

 

Paul Jackson

[Yamanx]

Hi Tony

 

Thanks for advice. After further experimentation I think the govenor valve may well be jamming abd the most likely cause of my grief. Do these things wear. If so which bits should be renewed? Or do you just strip and clean it all out?

 

thanks

 

Paul Jackson

 

This needs to be done by a specialist, not something you can just strip and clean out I'm afraid.

[Tony Brooks]

This needs to be done by a specialist, not something you can just strip and clean out I'm afraid.

 

 

Not quiet true, but it is if you want a long term reliable result.

 

Whilst "up river" with hire boats that have stopped because they filled their fuel tanks with water I have removed the whole "turret" (two hex screws) and carefully lifted the governor valve clear of its housing and then rinsed/blown the water droplets away. Then drained the tank and flushed the system - including out of the hole the governor was fitted into (I will not go into details) before reassembling taking great care over dirt. This always got the boat close to the van for a pump change. Even done it with a small pair of water pump grips, a hammer and screwdriver when pushed.

 

Tony Brooks

[RobinJ]

Hi all you engine experts out there.

 

I have recently bought a narrowboat with a 1500 BMC Diesel engine.

 

It has started showing a tendency to overrev quite drasticaly for no apparent reason. When left at say 1500 rpm on a fixed throttle setting the revs will suddenly start to build and then become totally unreponsive to throttle adjustments. Only a shut down will prevent a meltdown. When restarted the engine will then appear to be OK again.

 

Any suggestions at what I should be looking for, checking?

 

Paul Jackson

 

Two reasons gnerally why BMC's do this:-

1) Sucking oil - excessive back pressure, fumes from oil filler - kink in breather or blocked filter, condensed oil blown into intake.

What sort of valve seals are fitted?

Setting the valve clearance properly may help, but it could be a sign that either the valve guides or the rings are getting worn.

2) Sucking fuel - usually leaky lift pump, but can also be air leaking into fuel pipes.

Does the oil level go up when it is left standing with the fuel on?

The diaphragm can split, but sometimes fuel just leaks past the rivet in the middle!