Car is 350SDL 6 cylinder diesel with intermittent rough idle and serious injector knock when cold (sounds like one cylinder). Do the pressure valves in top of the fuel injector pump ever need replacing? Can replacing the seals around them cause failure? I didn't have the problem until a shop replaced the seals.

Thank you.

EZ:

I got my 300D for $5000 because someone appearantly replaced the 0-rings on the pressure valve holders and didn't torque them down properly. Serious injector knock on #4, with #2 and #3 noisy too -- plenty of fuel delivered with the injector cap nuts loose, new nozzles, OK compression (very low on #4). Very rough idle, poor power until the turbo came up, but no smoke and good milage, ran fine in the highway, didn't use any oil (still doesn't).

Seals and o-rings cost me about $8.15, only took about an hour to change them. Fixed the rough idle (very rough, since #4 didn't fire at all most of the time).

I don't think you will go wrong -- very easy. Remove injector lines completely. Remove the locking rings around the pressure valve holders, then unscrew then one at a time (need a special splined socket, $30 or so from Snap-on or maybe you can borrow one, I did), lift the seal off the top of the pressure valve, replace o-ring (if yours are new, don't bother), then reinstall the spring and holder. Torque to 25 ft/lbs three times -- the seals give quite a bit, and if you don't get them compressed....... Reinstall lock rings and injector lines, leaving the cap nuts on the injectors loose. Crank at full throttle until all the air is out of the lines, then tighten the cap nuts and crank til it starts.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!