knocking
 

My 1990 f superduty with 7.3 is knocking at 3/4 to full throttle. I know it is not a rod or lifter knock. All the clearances have been checked on those items. could it be injector knock, I'm used to diesels with common rail injection and turbo so I'm learning as I go on these non turbo engines. It also Idles at about 850-875 RPM any ideas on that also. Thanks.

A bad injector can cause a fuel knock. If you could figure out which cylinder is making the noise you could have that injector tested.

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One other possibility that has driven me crazy a couple of times is a broken piston skirt. It sort of sounds like a valve noise but is hard to locate. a mechanics stethiscope might help if that is the problem

Thanks for that bit of advice there, I know as the RPM goes up so does pressure and with pressure comes more noise, so that would make sense to me. how hard are the injectors to pull and replace. I know all about the bleeding and that, just the injector in and out itself. Thanks alot.

Like most things now it is more about getting at them than getting them out. After you have taken the injector line and return line T off they just unscrew out of the head. they are on the intake manifold side of the head so there may be wiring or brackets in the way of getting at them. The autozone website has repair manual information for free. All you have to do is register on their site and you can acces the manual online.

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