White smoke on over-run

My Series 3, 5mb 2.25 Diesel engine has had the injector pump timed by trial and error. It now seems about right with no knock on acceleration under load with minimal black smoke. However it white smokes a lot on the over-run. When out of gear and after the throttle has been blipped it white smokes a bit as the revs die down but has no white smoke once it reaches idle. I suspect that something is worn in the drive train to the injector pump which is causing the timing to temporarily retard but I haven’t removed the pump yet to investigate. What should I be looking for? For info the timing chain and tensioner were replaced about 400 miles ago.
Edward

I think you will find the timing needs to be super accurate spot on, near enough is not good enough, otherwise you are on a hiding to nothing.

Have an ask on the series 2 forum, some very knowledgable guys on there.
Pretty sure there are some very detailed threads on how to set the pump up, might have to ask as last time I was on there the search function was next to useless.

Edward George said:

My Series 3, 5mb 2.25 Diesel engine has had the injector pump timed by trial and error. It now seems about right with no knock on acceleration under load with minimal black smoke. However it white smokes a lot on the over-run. When out of gear and after the throttle has been blipped it white smokes a bit as the revs die down but has no white smoke once it reaches idle. I suspect that something is worn in the drive train to the injector pump which is causing the timing to temporarily retard but I haven’t removed the pump yet to investigate. What should I be looking for? For info the timing chain and tensioner were replaced about 400 miles ago.
Edward

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Many years since I have done one of those.
However, are you sure that the timing chain replacement was done properly? A tooth out, and it will still probably run, but not perfectly.
Also, from memory, wear in the drive gear from the camshaft, and the drive piece that slots into the gear, are not uncommon.
Many pumps that age may be showing internal wear as well.

Thank you Lynall and Turboman. Unfortunately it is the later pump without the internal timing marks and I don’t have the special timing tool. At well over £200 to buy I am probably stuck with trial and error small pump set-up adjustments for now. I had thought about wear in the drive gear from the camshaft and had planned to buy a new quality ETC6139 gear drive shaft and bush from Turner Engineering. Unfortunately it is out of stock and I’m not aware of anyone else who can supply a guaranteed well engineered one. Perhaps I should start by removIng the injector pump and measure the backlash and bush wear in the drive shaft currently fitted.

I should have mentioned that the injector pump was professionally reconditioned and the injectors recalibrated and tested about 400 miles ago. I didn’t fit the new timing chain and tensioner myself but the engine seems to run well enough now apart from the white smoke, so it’s hopefully not a tooth out and I won’t attempt to remove the timing cover just yet. Worth me raising with the Series 2 people as well. Someone there may well have come across this feature before.

Edward

White smoke at tick over is usually the result of retarded injection timing, or a dribbling injector causing unburnt fuel, resulting in clouds of white smoke. You said it clears once back to idle. Have you got a brake butterfly on the manifold?

tony109 said:

White smoke at tick over is usually the result of retarded injection timing, or a dribbling injector causing unburnt fuel, resulting in clouds of white smoke. You said it clears once back to idle. Have you got a brake butterfly on the manifold?

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Thanks tony109
Because it only happens on the overrun I think it is a worn gear or bush under the injection pump causing backlash and a retarded pump setting. I tried to get a replacement from Turner Engineering but they are out of stock. Not sure what you mean by a brake butterfly.

On overrun fuel should be close to cut off if not cut off completely. Butterfly is in intake to hold vaccuum for brake servo on overrun. Not fitted if you have vacuum pump.

You have the pump timing to far retarded...give it a tad more advance...only 1mm of rotation of the pump at a time...keep going till its sounds a bit harsh...then retard just a bit.
Do you also find on cold start at idle it has a bit of an uneven exhaust note...with blue smoke?

Thanks rob1miles and nickjaxe. I’d understood that on the overrun the injector pump closes fuel delivery down to an idle setting. Therefore if there is wear in the drive skew gear or its brass bush, this can cause the timing to retard until the engine reaches idle speed, causing white smoke. The Landy does not have servo brakes so unlikely to have a butterfly valve but I will check. The engine is a bit uneven at cold idle where it sometimes misses and throws out white smoke for a moment. It idles evenly when warm with no smoke. I think I will remove the pump and check the drive gear and bush, replacing if worn. Then I can replace the pump and adjust the timing as suggested.
Edward

Wear is taken up as you adjust.... is white...some people mix light blue with white....well if it is white you could have an injector prob...does it start well from cold.

You ever had any injector work done.

It starts well from cold with heater plugs. The injector pump and injectors were overhauled and recalibrated by a pump specialist a few hundred miles ago. I think what I am saying is that on the over-run the engine is performing some of the braking effort. It is no longer driving the car. So any wear in the engine driving components is being taken up. Therefore if there is wear in the drive components between the camshaft and the injector pump, the wear is taken up and this has the effect of retarding the timing until the engine reaches idle speed and the vehicle is either at a standstill or clutch depressed or in neutral. Hence the white smoke on the over-run.

It is odd that its on the over run only and not idle too as they fueling should (am I right?) be the same. The lumpy idle does suggest that getting that right may solve the over run too.

the fuel pump fitted to 2.25 should cut off fuel entirely on over-run from high rpm. it is only later 2.5 types that had ant-istall settings which trickled fuel in even at high rpm with throttle shut.

cam chain timing is critical on early diesels. i used to find exhaust peak with DTI gauge to set chain properly

Thank you rob1miles and adrianhogg.
The smoke occurs on overrun even if the engine is only revved slightly. I think I will try advancing the pump timing slightly to see if the smoke clears without the engine sounding harsh in normal running. If unsuccessful I will check for wear backlash in the pump skew drive gear. The cam chain timing will be another thing to check. Because the pump was overhauled by a specialist I have to assume for the moment that fuel shutoff settings from high revs are correct.

I would go for timing or an injector problem. Have to got access to the kit to set the injector pressures ? I've had injectors professionally overhaled and they where a disaster. Pop off pressures should be 130 bar, once I had set this correctly all my troubles went away. My professionally done ones varied from 80 to 170 bar.
Be sure to get the old sealing washers out and replaced when messing with the injectors, I use a pencil to fish them out.

Thanks divie.
Yes I have access to a pressure tester. I can check the spray pattern at the same time. I’ll get a good torch so that I can ensure all the old washers have been removed. Lots to do now so I’d better get cracking!