Hi
I just changed the engine and trans mounts on my 1985 300td. Now when I start it (starts right up)- it idles smoothly but after a few minutes begins to miss on one or more cylinders and starts shaking. I then changed out both fuel filters and bled the system. This didn't improve anything. The clear pre-filter has an air bubble in it but the air doesn't seem to be going anywhere.

All ideas welcome.

Joseph

So far it sounds like an Air Leak. When you changed the Plastic Primary Filter did you also change the Fuel Hoses there.
I found on mine that the old Hoses were hard enough that even after I tightened the clamps I could twist the Plastic Filter by hand.
Other thoughts
If before you did the Motor Mount change your Fuel Hoses going to the Fuel Supply Pump were sort of tight; raising the Engine up could have pulled them tighter and maybe done something to the plastic tube that the rubber hoses attach to.

Another source of an air leak can be the Hand Primer. If you have the old style Aluminum tube one with the hard plastic Knob besure to push it all the way to the bottom and turn the Knob clockwise and tighten it in the down position. This is supposed to seal it at the bottom.

It is normal to have a bubble in the Plastic Filter.

You did not say if the miss goes away after you run the car at higher speeds or not?

Run the car with out the Fuel Tank Cap on to see if it is a tank venting problem.

Swap the Fuel Inlet hose with the Fuel Outlet hose. This will bypass the Fuel Tank Screen. If your car works better when you do this the Tank screen may be plugged.(I think you need at least 1/2 tank of fuel for this to work.)

When was the last time the Valves were adjusted?

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84 300D, 82 Volvo 244Gl Diesel

I presume this happened after the mounts? the small bubble in the clear filter is normal. With the engine running, crack open each hard line at the injector letting the fuel drip and the engine should drop a cylinder just like removing a plug wire from a running gas rig. As each injector hard line is opened the miss or roughness should feel the same. If, after cracking one open and the result is less than the others, then that injector is either dirty or the injector pump is the culprit. Do this after you have looked at what DIESEL911 recommends.

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81 300CD (sold) 1972 280 SEL 4.5 (sold) 1966 250 S 4 spd (sold) 1974 450 SL (sold) 86 BMW 325ES (sold), 1973 280C (sold) 1988 300 SE.

1984 300D TURBO 149K
INSTALL A NEW FM-100 STANADYNE WATER FILTER UNIT AND FILL FILTER WITH DIESEL PURGE, LEAK AT THE FUEL HOSE OUT, CUT 2 INCHES OFF END REINSTALL HOSE AN NO MORE AIR IN PRIMARY FILTER, HAD BLACK FUNGUS IN PRIMARY FILTER, USE BIOBOR FROM A BOAT SUPPLY, WITH FULL FUEL TANK THE FILTER IS NOW CLEAN AND GOOD POWER, USE A 5 MICRON FILTER ITS $80.00 UNIT ASSY. INSTALL NEXT TO WINDOW WASHER WATER TANK
ENGINE IDLE IS OK AFTER REPAIR AIR LEAK.

Thanks Guys

I did change out the hoses with the filters and it has the new style pump. I couldn't find any damage to the plastic lines. I did a valve adjustment not long ago but I suppose its possible that I didn't lock the adjustment nuts well enough. I put a can of Sea Foam in the fuel tank in hopes it might help with moisture or unstick something but it really has not been run enough to have a chance to work. Seems to run smoother at higher RPMs but goes sour and soon as it returns to idle. From what I can see, the fuel is flowing into the clear filter at a good clip and looks perfectly clean. Opening the gas cap doesn't do anything.

I guess its time to try cracking the injector hard lines to see what I can discover.

Q: If I've I've got a dirty injector or two - is there a way for me to clean them?

All suggestions appreciated

Joseph

Are you using only Diesel Fuel?

I have seen Injector Spray Nozzles that the Pintel inside of the Spray Nozzle would hang up due to haveing had water that rusted them or dirt passing through them.
Sometimes the problem Injectors will stick when you Pop Test them but not always.
When you take them apart you can see score marks on the side of the Pintel.
Were I worked we had an Electric Motor with a small Drill Chuck on it; we would put the Pintel in the Chuck; put some extremely fine lapping compound on some Toilet paper; spin the pintle and polish up the sides.
After the Injector was assembled it would be retested.

But, you would think that if an Injector was having a problem it would also have the same problem when the Engine is still cold.

There is some threads from Members who have done a Purge to clean out from the Fuel Supply Pump to the Injectors.

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84 300D, 82 Volvo 244Gl Diesel

Hi & Thanks for the prompt response.

I only use pump diesel fuel.

I too am confused as to why it starts out running smooth and then turns sour. Is that something air in the fuel would do? Or perhaps some malfunction of the IP?

I don't want to just start throwing money at it without understanding the problem.

How do you feel about a Diesel Purge or Italian tuneup for something like this?

Other Ideas?

Regards,

Joseph

Search for Surfblau's post: "300TD Hot Idle Shaking - apparently solved" for a list of common places to start resolving this problem. I'm having a similar problem and am going to start with Diesel Purge, which seems to be what everyone is recommending. Then the governer screw/rack damper screw. Sometimes BioD will run smoother in my case and might be worth a shot for you...not sure why, but someone on this post prob does. It could be bad compression too...I think compression should be about 150 and if it's less than 75% of that it will make the engine shake excessively.

150 sounds like a gasser,, diesels should run 350

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1981 240D 143k 4 spd manual -SOLD

2004 VW Jetta TDI 5 speed 300k -still driven daily

After I changed out my motor mounts on my 1985 300td I had a problem that the engine would idle well cold and then start to miss and shake as it warmed up. Following advice from members, I changed out the fuel filters & fuel lines, cracked the injector lines to verify that all the cylinders were working and did a diesel purge. None of which helped.

But another member suggestion did the trick - screwing the rack damper bolt in -now she just purrs and purrs.

I never would have found the problen without the help of the forum.

Thanks!

Joseph

Screwing it all the way in will cut your full power potential and can cause hard starts and stalling in colder temperatures. The ideal way to tune out the shaking is to both adjust the idle speed and the rack damper to a perfect sweet spot. It took me 40 minutes under the hood of my SD to find that spot....but right around 750ish rpm with the rack damper out a couple turns, it runs absolutely smoothly, 0 shake at all. Well worth having my face by a hot idling engine for 40 minutes.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Where is the racker damp bolt located?

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85 300D 180k

Lower rear of the injector pump, by the oil filter

How long is a few minutes? Sure its not happening with the GP cut off?

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1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42