91 350SDL Surging

If it were only the injection pump!

These 3.5L diesels have a long and sorry history of bending their connecting rods - probably metal fatigue. The #1 and #4 pistons are usually affected and are no longer square to their cylinders causing the cylinder walls to be scored. The engine surges, burps, grunts, begins to burn oil and finally is no longer reliable. This will not be cheap to fix, sorry.

Many of these 3.5L have been rebuilt and replaced at considerable expense to owners. You'll find more information from a Google search. also see:

Re: 91 350SDL Surging You may want to look into cap,ignition wire,plug and air filter first.good luck

Let's not go overboard here, just because it's 603 engine, and a 91 350SDL this guy thinks every tweak and rattle on 603 is the known engine problem. This person was explaining a surging, not the symptoms with bend rods and scored cylinder walls!, I'm sure his question would have been more precise. I have a 93 SD and recently rebuild the cylinder, had I blieved all the other mechanics I would have had to replace the engine. I was burning oil and after I replaced the valve guides and seals my problem stopped. I absolutly love my SD. I suggest you find a MB shop that properly diagnoses your vacuum related engine surge. The problem could be several vacuum connections I can think of, just make sure you find an independent shop that doesn't wanna rebuild your engine everytime it tweaks or rattles.

Most certainly that always made my Diesel run better, although if you grind those parts up they fit into the tank easier. Martin Autobahn Auto

You're not supposed to put them in the tank! You are supposed to hang them on the mirror as a voodoo totem.

Speaking of plugs......tried the Platinum plugs in my diesel. I found the performance declined, so I went back to the regular plugs. Thought it might be a bad cap......it wasn't........ ;)

You need to try the ones with four electrodes, that really helps!