Tapping/Knocking noise - Diesel Forum

VWGuy · 05-02-2005, 09:21 AM

Hey guys,

Got a few things going on with the ole truck. I've started to notice a tapping sound (it seems little too high pitched to call it a knock) from the motor. It does it usually pulling away from a stop sign, and goes away at around 1500 rpms (give or take a little). Also, and this started about the same time, first thing in the morning shakes pretty bad, and blows a bunch of blueish smoke out the exhaust. The smoke goes away after a few minutes or so, but the shaking comes and goes througout the day at stoplights and low rpms. Sometimes it will idle smooth, and sometimes it will shake. It did this a few months ago (the shakin, not the smokin), and I replaced all the injectors and it ran perfect, I mean like a new motor, for about a week. My main concern is the tapping right now, even though they are probably related, I'm just afraid if its coming from the bottom end (bearings), or would that be a deeper knock. Any suggestions?
Thanks, Ben.

Paperboy · 05-02-2005, 11:22 AM

Sounds like you may have an air leak in your fuel system. Air in the lines will cause the stumble, blue smoke, and the knocking sound as the air will alter the injection timing until it is passed...

How full was the fuel tank? When you replaced injectors, did u replace return lines as well? Have u messed with the water seperator?

Good luck. ~Vince

VWGuy · 05-03-2005, 07:27 AM

Thanks. I was hoping it would be something along those lines. I was leaking fuel pretty bad after I replaced the injectors, and it ran like this, found the leak and it went away for about a week, but this time I don't see it leaking fuel anywhere. I guess you can still have an air leak and not be leaking fuel?