E300D Rough and Smokey on start up

[D1ngbat]

I have a E300D 606 engine 1996 N 265000 miles.
On start up it seems to be missing one or more cylinders creating engine rocking and plenty of smoke.
I have had the injectors and glow plugs replaced and far short of taking the head off Iam not sure how to proceed. Needless to say once the engine is hot it runs sweet. Could it be carbon build up? Any ideas, cheers

 

[television]

Welcome Dingbat,, is the car easy to start, or is there much cranking

 

[D1ngbat]

No problems at all starting

 

[television]

OK wait till one of the diesel guys come on

 

[simon_wall69]

I assume that the glow plug light is going out. Could there be a compression issue?

The smoke is just the unburnt fuel in the cat from not running on all cylinders. I would think if there is excessive carbon then the problem would not just be when cold. Mine had a problem with a misfire from excessive carbon and it was cured with an Italian tune up and an injection treatment. Did 3,000 miles around Europe over Christmas without a problem afterwards.

 

[D1ngbat]

My engineer tells me that compression is fine and the glow plug light does go out

 

[Number_Cruncher]

>>My engineer tells me that compression is fine

Mechanic - probably, technician - possibly, but, engineer, most unlikely! An engineer might have designed or developed the car, but is very unlikely to be fixing it for you!

However, if the compression is good, there are a couple of things to check;

1) that the coolant temperature sensor for the glow plug controller is working (the wiring to this sensor can degrade and short out)

2) that ALL the low pressure diesel pipes have either been replaced, or at the very least had new O rings fitted. The O ring seal on the fuel pre-filter is also frequently a problem. The injector leak off pipes also become brittle and leak - if they haven't been replaced during the last year or two, it's worth putting new ones on.

 

[D1ngbat]

Thanks for information, buy the way, Mechanic, Technician or Engineer all the same to me around £40/hour

 

[HERBIEMERCMAN]

e300 poor cold starting.

hi dingbat, i have a boat with two of these engines marinised. when i start them from cold i get exactly what you are describing, despite having new inj/glow plugs,a friend of mine who is the manager of "merlin" diesels, (top notch company) in preston, lancs, that cause in my situation is engine oil seaping passed the valve guides into the combustion area, some cylinders will be worse than others, hence the rockin and rollin. engine oil mixed with the diesel fuel is hard to burn and you get lots of smoke for two or three minutes.once warm everything ok. oil consumption is not noticeable, we are talking about a very small amount. best of luck. herbiemercman.

 

[meatballs]

It could possibly have an air leak on the pump or on one of the fuel lines,Ive had this happen to me before on an old/high mileage diesel car.A fuel pump repair kit cured it (throttle spindle was worn - if you moved it side to side it reved slightly).Whilst parked overnight,air was drawn in and made it run lumpy for a while on start up.

 

[Number_Cruncher]

Re-reading my post, it's clear that I didn't put anywhere near enough emphasis on the problem of the low pressure pipe and pre-filter O rings - these are absolutely notorious for leaking air and causing starting problems on these engines, and should all be replaced as a matter of course.

If the car is a W210, there's also a hidden O ring behind the shut off valve which is bolted onto the side of the injector pump - this needs to be changed too.

If you plan on using any spurious types of fuel rather than pump diesel, it's also worth considering replacing these O rings with Viton type O rings which are more resistant to the nasty DIY fuels than the standard type.

 

[Parrot of Doom]

Crack open the glow plug relay unit (should be right side of engine bay near the windscreen) and check the fuses are intact:

 

[Bolide]

A laser / infra-red thermometer will let you watch the exhaust gas temps as the engine warms up - that might clue you in a bit. You could also run the glow plugs for two cycles without starting the engine and measure the head temps by cylinder. Obviously if it's not burning the fuel the exhaust temp will stay low so measuring the temp on glow plugs only will tell you whether it's related to glow plugs or not

I'd be interested to know which cylinders are misfiring. The 606 suffers from valve seat recession on cylinders #5 & 6 (rearmost cylinders) so I would not be at all surprised if #1 was slow to come up to temperature

If you have the head off at any point budget for a couple of inlet valves and an exhaust valve - they're sodium-filled but not outrageously expensive. Also have the head planed and the valves ground in

At that mileage I'd assume moderate VSR and expect a top-end rebuild would bring a lot of life back into the engine. As they lose compression they go very flat

Nick Froome
www.w124.co.uk

 

[Number_Cruncher]

>>cylinders #1 & 2

It was the inlets on 5 and 6 on mine, and it needed new seats as well as valves!

 

[Bolide]

>>cylinders #1 & 2

It was the inlets on 5 and 6 on mine

Is 5 & 6 the front or back of the engine? Never can remember

Nick Froome
www.w124.co.uk

 

[Number_Cruncher]

Usual practice for inline engines is to number from the front, so, it was the rearmost 2 cylinders which gave me trouble.

To complicate matters, many French inline engines are numbered from the flywheel end, i.e., the reverse of normal practice (Gallic charm?!!) and on V engines of any make, the numbering scheme is made up as they go along!

 

[Bolide]

In which case all the valve problems I have seen have been on #5 & 6 and I'll edit my original post accordingly

It's the back two under the bulkhead that always seem to have VSR

Nick Froome
www.w124.co.uk

 

[Number_Cruncher]

>>It's the back two under the bulkhead that always seem to have VSR

I think these cylinders towards the rear of the engine tend to run hotter than those at the front.

The inlet valves are also very poorly lubricated, and in this respect, I think that keeping the small holes in the crankcase ventilation rubber elbows in the inlet manifold clear is important, to allow some lubrication via the oil mist in the crankcase fumes. Very little oil is burnt via the valve guides as you'll have seen when you look at the backs of the valves.

Some good info here:

http://www.shef.ac.uk/mecheng/tribology/research/projects/resvalve.htm

 

[D1ngbat]

Thanks, Number Cruncher and Bolide some really useful stuff there. I think the troublesome cylinder is No 6 but I am told it doesn't loose compression. With the manifold off (small amount visible) there is quiet a bit of Carbon Build up. The car is going in tomorrow and I am loathed to take the head off. The rocking at idle and smoke vanishes at 40 degrees and even in this cold weather I can live with it. However, if taking the head off is the only course of action then maybe I will dip into my pockets and get the engine re-conditioned, any suggestions?

 

[Number_Cruncher]

If the compression figures are good, then, there's no reason to take the head off. It's not a trivial task!

However, I didn't do a compression test to find the problem I had - it was more obvious! After replacing some leaking fuel pipe O rings for which I had removed the inlet manifold, I plugged the exposed vacuum pipe ends and started the engine to check for leaks. The exhaust smoke chuffing back out of the inlet ports on cylinder 6 told me all I needed to know!

For the fault you've described, a really carefull and pedantic checking and replacement of the low pressure fuel pipe, pre-filter, and (if applicable) shut off valve O rings is the place to start - they're quick and cheap to do, as opposed to taking the head off, which is difficult and expensive!