1986 300sdl , At idle smokes fuel smoke and loud knock with and intermitent stumble or dead hard miss. At speed smooth but can still feel a faint intermitent miss (da...da.da.....da...da....da..da)

I found by cracking the injector lines when #6 was cracked open the knock went away and she idles smooth.

So I got one new injector... same thing same cylinder, no change.

Any other simple points to look for or is it pull the head time??

Thanx,
Dave

You have to be careful deciding what to do in my opinion. You have no positive indicator that it is the engine or the number six injector pump element is out of sequencial timing.Or even some other possibilities. You could start by doing a compression check and if engine is fairly equal move on to a milli volt test to see what kind of heat that cylinder is running at in comparison to the others. Of course check the cam lobes.
If it turns out to be running a lot hotter than your other cylinders with guidance you might try a correction. If the cylinder is running colder it opens up a few more possibilities.
It almost sounds like the number six element is advanced in timing to me. Or something is causing that effect. You might want to recheck the replacement injector by swapping number five and six injectors before anything.
Even if it where the pump things are pretty good as that element is not worn out or it could not do this. It would be late injecting with no knock. One concern I have is your description. It almost sounds like you are describing a knock and a periodic miss. Almost like two separate problems. Since I am not a working mechanic I have to leave it to others to interpret. Anyways just my thoughts and opinions.

Did this issue develop slowly over time.........or was it a sudden event?

Although the IP might be the culprit........generally, it would simply not provide the quantity of fuel desired.........and the power in that cylinder would be lower then the other cylinders. The characteristic injection knock would more likely be injector or prechamber related.

If the prechamber is damaged in any way........or the holes are clogged.......such a symptom is possible.

I wouldn't be pulling the head without a compression test and a prechamber removal first.

One more thing also. No more high speed running with this condition. It could damage a piston. Low speed even is not really a good ideal either.
Edit: a lot may depend if you aquired the car with this condition as well. Your low post number tends to make it a possibility.

Delivery valve?

i agree do not do high speed. modern combustion engines are not designed to have an explosion, inside of the combustion chamber. its supposed to just burn and have the expanding gasses push the pistion down. but when you hear that knock its injecting too soon. and the diesel is exploding in the cylinder pushing against the pistion with extreme pressure. if you do it enough it will weaken the pstion and eventually put a hole right in the top of it. then again low speed running will wash the cylinder walls with diesel of that piston and will ruin the rings very quickly.

__________________
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?

As long as they would add one additional commandment for you to keep thy religion to thyself.
George Carlin (Wonder where he is now..)

1981 240d (engine donor 1983 240d) recently rebuilt engine hurray! - No more.. fought a tree and the tree won.

pearl black 1983 240d 4speed (Converted!@$$%) atleast the tranny was rebuilt.

Thanx,
This is ceratinly a proactive board.
I am goin da pull the injector check the chamber and swap it with #5.

Don't worry I ain't gone more stuff yet to come.

I have 2 of these beasts. an 84 300cd, she is old reliable, and a 86 300sdl nice big car that my ex sis in law gave me. They didn't give the ex the time of day.

I want to get the sdl up to snuff to haul kayaks and pop-up camper for camping dates with ALL my new girl friends.

BTW guys there are ALOT of good looking chicks 47 to 52 with money that love the outdoors that need us!!!!

Women are tired of "Metrosexuals" they want regular guys.

Runnin the Milk route,
Dave

Dave, have you noticed any fuel leaking, or wet injectors? Also when you swapped the injector did you not the condition of the heat shield? did you have the injector "POP" tested? I too have experienced the miss and raw diesel smoke but need more information to assist.

__________________
Dean

Got her all taken care of.
Runs awesome and quiet.
Ended up being bent connecting rod in #6
Talked to previous owner they drove it for 4 years knocking and just thought that is how Diesels run.
Now no smoke on start-up and .
Found used rod, had head ck'd,

Thanx for all responses

Dave

More details please.

We're quite interested whenever a rod is found to be bent on this engine.

How did you diagnose this?

What drew you toward investigation of such a condition? It's relatively rare on that engine. Compression test?

What did the rod look like? Bent transverse to the engine axis.........or longitudinal to it? How much was the bend?

Did the bent rod cause excess cylinder wear in one axis?

What's the oil consumption?

Any and all details appreciated..........

TKS.

What I found,

Motor had loud diesel nail at idle

Knew I had low comp on #6 she read 240psi.

Could have been several things but I knew the head had to come off.

Was expecting to see blown head gasket or a valve problem.

Yet there it was #6 piston about 1/8" lower than #1.

Pulled the motor up at an angle just enough to drop the pan, pushed out #6 piston and thar she was "banana rod". Bearing was perfect, cylinder not a mark in her. Bend was in line with rotation. Not kinked sideways.

Shoved a used rod and piston assmy. machine shop ck'd head was perfect they did touch up the valves since they were out. Put it all back.

Runs awesome, no smoke at start, sounds like a Singer Sewing machine at idle, no oil use yet it never did use oil,

Previous owner drove this car abput 200k with this condition. Tough!!!

Been commutting 100 miles a day for several weeks now awesome mileage and runs cooler.

Now she is worth the needed paint job.

Dave

Excellent work. A bent rod is the last thing we typically think of on these engines. They are common to the later 603.970 and .971 engines, but, this is only the second one that I've heard of on the forum.

Good luck in the future with it.

Great story with a happy ending. I know what you mean by that sewing machine sound at idle. I can't get enough of it from my OM606. It's better than music. The TDI sounds good too, but not as nice. It's more like an air compressor.

__________________
2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

'Heck with the cars, where are all these 42-52 year old women with money that need us?

Stop by any college. You'll find them