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Car Forum / Mercedes-Benz Cars / February 2008injectors & nozzles
Hi all, I finally got around to checking the compression on my 1984 300SD. 400 in all cylinders with 100 or 125 on the first crank for all of 'em. I guess that's pretty good. The engine has 215K on it. When I pulled the injectors out a couple of them had a lot of black soot around the nozzle. I gently ran my finger across the tip as I was told that if it snags your finger it's time for a new nozzle. They all seemed fine for that test. I've been running biodiesel in it for a couple of months now and will be switching over to waste veggie oil soon. Should I leave well enough alone or should I change out the nozzles at some time as preventative maintenance? Thank to all, Jeff If it starts well, doesn't knock when cold and runs smoothly leave it alone. One can always change the nozzles ... later.  Signature© 2008 T.G.Lambach. Publication in any form requires prior written permission. WVO takes much more effort to get a fine mist spray pattern than diesel fuel... and for your car, the rebuilt injectors are dirt cheap... $35 each! and you need only 5 of them. Change it out. Don't forget new heat washers. 100 PSI? On the 1st stroke is not enough. Unlike an ignition spark gasoline engine, a diesel fires on compression. That 1st stroke of compression is what fires it off. 5 or 6 strokes added together does not mean squat. Minimum compression is 16 bar. 1 bar or 1 atmoshere rounded up in PSI is 15. 15 x 16 = 240 PSI. > Hi all, > I finally got around to checking the compression on my 1984 300SD. [quoted text clipped - 15 lines] > Thank to all, > Jeff So, then, a new engines should read 400psi on the first stroke? Also, I did the test on a cold engine that had sat overnight. Was that the right way to do it? Thanks, Jeff You start your car after it sits overnight...... Same cold 1st compression stroke that makes it run. > So, then, a new engines should read 400psi on the first stroke? > [quoted text clipped - 4 lines] > Thanks, > Jeff I thought the compression reading is taken at the third compression... third jump... not first jump. Then again, this was for gas engine... > I thought the compression reading is taken at the third compression... third > jump... not first jump. Then again, this was for gas engine... I'm sure it was up to 300psi by the third stroke and they all topped out at 400psi. In any event, the car starts fine when it's cold, doesn't blow any smoke and doesn't burn or leak any oil and seems to run real smooth--so I'm happy with it so far. Jeff |
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