BMC 1500 idling problem, engine does slowly fall back to idle

[ALEX4777]

When the engine runs and I rev it up and down again, it takes a long long time before the engine finally comes to the idling rev it should be (I guess 800 rpm).it falls down to i.e. 1500rpm and then after some time back to 1000 and slowly back to what it should be. (rpm only for example)

 

Some background. 6 months ago the shaft of the injector pump was broken. We were able to get it repaired in the Netherlands for an acceptable price and remounted the injectorpump.

(In the mean time we have replaced the diesel filter, added a waterseparator and replaced all fuel-linings and removed the plugged and fouled lubricator oil filter.)

 

The first time the engine was running it went immediate to high rev. We've adjusted the adjustable screw at no5 to allow the throttledisc to go back further to allow low revs. Now it seems to work good, but only it takes very long before the engine revs back to low idling speed. Up to 10-40 seconds or so, which is quit dangerous when boating in the Amsterdam canals. We operate the throttle at the injector pump, so it has nothing to do with the throttle cable or so. Before the shaft was broken everything functioned OK, so I think it has to do with the injectorpump.

I guess we have to adjust something at the injector pump. I've attached a numbered picture.

Any advise what to adjust on the injectorpump?.

http://i1333.photobucket.com/albums/w626/lexisernu/dieselpumpnumbers_zps6e6dc636.jpg

 

bold/screw adjusted by me to get it back to normal idling http://i1333.photobucket.com/albums/w626/lexisernu/idlescrew_zps567e328d.jpg

 

looking forward to your reply.

 

Alex

Edited April 14, 2014 by ALEX4777

[Tony Brooks]

This pump looks a bit odd to me because number two normally has a bleed screw in the top of it. However two and its lock nut is an idle stabilisation damper and if the screw (2) is screwed too far in it will not drop to idle.

 

It looks to me as if that screw is a long way in. I have known pumps returned form the specialist in this state.

 

Try slackening the locknut and unscrewing 2 a flat at a time. Each time rev the engine and see how long it takes and if it will drop to idle. You wll porbbalu have to adjust the idle adjusting screw (as you identified) as well.

[ALEX4777]

Hi Tony, thanks for advise. I will give it a try next weekend. Any idea where are 1,3 and 4 used for?

you are right about the bleeding screw. I was surprised as well, after looking in the bmc manual, but it always has been this way and according to some people I met (not specialist like you) you wont need to bleed the system at this point???

I read in the manual also something like a max rev limiting screw. Does that make sense to you?

 

regards, Alex

[Tony Brooks]

I have no idea what 4 is and do not recall seeing one on a BMC 1.5 DPA pump before. This is why I said the pump looked a bit odd but there are many different types of this pump so who knows. From its position and knowing what is inside the "turret" I wonder if it is a bleed screw. I agree the one that is usually on top of item 2 should not normally be used. Far too many times I have seen it lead to maladjusted a dampers or the whole assembly wrenched out of the "turret".

 

The spindles for the stop and throttle control have waists machined into them and items 1 and 3 do two jobs. They fit through the waists so thereby retain the spindles in the housing. They also hold the "turret" onto the main pump body. If you ever removed the control cables and took the screws out you could lift the whole governor assembly off the pump body. The governor valve would be hanging out of a hole in the bottom. If you then pulled the control spindles out the governor valve would fall out. It is a very small item for such a large chunk of kit. Do not do this unless a seal leaks or you get water in the governor. If you do observe absolute cleanliness, a speck of grit can jamb the governor valve, as can water globs.

[ALEX4777]

thanks for clarification! We'll give it a try next weekend and keep you updated about my progress.

[ALEX4777]

One more question.

Can the idle problem have to do with the timing of the pump? We forgot to mark the exact position of the pump before removing is, but we think we've aprox replaced it on the same place (based on the print of the previous gasket). Anyway it is running, so i guess it will not be very far away from the exact timing.

Does any-one know the effect the timing is too far advanced or retarded?. (I do not have any special tools for exact timing as described in the manual, so i'am looking for a more practical solution if exact timing is critical).

[Tony Brooks]

The main effect of timing being a little way out is smoke, whiteish or blackish depending upon which way it is out.

 

The pump fits against a triangular adapter plate that is screwed onto the block. On one of the top corners (the front one I think) you should find a little metal pointer retained by two small set screws. When you fit the pump you should align a line scribed on the mating corner of the pump flange with the pointer. You only need the tool if you need to set the pointer or check its position. Over the years wear in the pump drive and timing chain will cause the pointer to be in the wrong position but if the engine starts well from cold and does not smoke more then BMCs typically do for a short while after the first start of the day do not worry about it.

 

Basically the tool takes the slack out of the timing and pump drive gear. If the engine is smoking after half an hours running and hot you could try slackening the three pump mounting nuts and twisting the pump a little to see if the smoke clears. Otherwise leave it alone.

 

The symptoms still indicate the idle damper.

[ALEX4777]

Hi Tony,

 

This weekend I'am going to give it a try with the governor idle stabilisation damper (if weather allows). I will let you know.

 

Regarding the timing, do you know which way to turn the dieselpump if white or blacksmoke appears. Clockwise or counter? and only for my curiosity. does white smoke means? too early or to late injection?

[Tony Brooks]

Hi Tony,

 

This weekend I'am going to give it a try with the governor idle stabilisation damper (if weather allows). I will let you know.

 

Regarding the timing, do you know which way to turn the dieselpump if white or blacksmoke appears. Clockwise or counter? and only for my curiosity. does white smoke means? too early or to late injection?

 

I knew once but have forgotten. I think white is vaporised fuel so will possibly indicate retarded injection. I am sure another member will be along soon to correct me.

[ALEX4777]

Hi Tony, unfortunately turning the governorbolt nr2 in and out did not had any improvement. on theidling problem. it take about 1 minutes to achieve high idling speed. It seems that is stepwise falls further back to normal idling, which allows changing gear.and then some later it drops below idling speed and the engine stops. moving the throttle, the engine pick up immeadiatly, but going down to idle is the problem. I think something inside is very slowly coming back to its idling position. (the governor?). I've turned the bolt nr 2 ( see picture) + and - 2 full turn but no effect at all. Now it's leaking a little round that screw tread of the bold and I don't dare to tighten the locknut any more, because it doesn't feel very good. I almost removed the governor assembly on top of the pump to have a look, but I didnot because I'am reluctant and do not know what might fall out. Removing the pump I try to avoid because is a lot of work because there's very little access. Any further advise Or tip is welcome.

Edited May 2, 2014 by ALEX4777

[Tony Brooks]

Nothing will fall out although a part will "dangle" as long as you do not remove the throttle and stop lever & shafts.

 

It just might be a bit of water/dirt/bug in the governor valve.

 

Make sure the non-return valve in the filter head (by the arrow going back into the filter) is not clogged up.

 

Carefully unscrew the LARGE hexagon union where the feed pipe attaches to the injector pump (observe cleanliness and watch out of the possibility of spring loaded parts) and make sure the nylon strainer below it is clean.

 

Both of these things are related to the fact that hydraulically governed pumps rev the engine when starved of fuel so it could be something else on the system.

[ALEX4777]

Hi Tony, I found your webside and was reading the articles about the DPA pump.(excelent article for newbees like me!!!). One thing surpricing me when I was yesterday at my boat. when the engine is off and I openend the ventscrew on the side of the Diesel HP pump, diesel was flowing out in a big stream. (without running the enginine nor priming the lift pump). Looking at the diagram of the metering valve, it think this should not happen so there's something wrong at the metering valve. What do you think? Is my conclusion correct. might this has to do with the cause of the problem?

[Tony Brooks]

Hi Tony, I found your webside and was reading the articles about the DPA pump.(excelent article for newbees like me!!!). One thing surpricing me when I was yesterday at my boat. when the engine is off and I openend the ventscrew on the side of the Diesel HP pump, diesel was flowing out in a big stream. (without running the enginine nor priming the lift pump). Looking at the diagram of the metering valve, it think this should not happen so there's something wrong at the metering valve. What do you think? Is my conclusion correct. might this has to do with the cause of the problem?

 

 

The metering valve/governor valve is "downstream" of the pump body and thus that bleed screw so it has no bearing on the fuel flow..

 

If the flow soon stopped then the cause was the lift pump spring pushing the diaphragm up. When the injector pump is "full" of fuel the volume of fuel in the lift pump holds the diaphragm down while the engine still waggles the drive mechanism up and down. When fuel is released from the system the spring under the diaphragm pushes the diaphragm up and delivers fuel, even on a stationary engine. If this is the cause it seem the 5/8AF (I think) banjo bolt holding the leak off pipe to the engine filter head has either been replaced by an ordinary bolt or the 0.5mm hole in the side of the bolt is blocked.

 

The other possibility is that the fuel level in the tank is higher than the bleed screw so fuel is flowing by gravity, that would go on until the level were the same.

 

I suppose someone may have fitted an electric lift pump that was energised at the time.

[ALEX4777]

sorry I mean the regulating valve. according to the diagram explaining the function of it in your article, i thought, for a not running engine, the transfer pump and the regulating valve together block the way for free fuel flow, but may-be I misinterpret the diagrams hoping to find a theoretical cause for the problem.

I'am not sure if this has been the case before, but may-be it has to do with the position of the engine/liftpump valves.

By the way the flow did not stop from the bleed and the position of the fuel tank is indeed higher then the bleedscrew.

 

(I appreciate your time explaining me the wonderfull world of BMC diesel very much!)

[RLWP]

The transfer pump won't prevent the flow as the valves both allow fuel to flow in the forward direction

 

Richard

Edited May 3, 2014 by RLWP

[Tony Brooks]

The regulating valve is designed so fuel pressure with a stationary engine can push it open, otherwise it would not let fuel through to allow bleeding. In those circumstances the regulating valve bypasses the transfer pump - see the illustration in the DPA sectino of the BT Notes on my website.