Hey guys, I've used this forum once before and got great results and I'm in dire need of help again. I picked up a 1993 7.3 idi today for $1200 bucks. Clean truck, 4x4, ac and heat and 5speed tranny all works amazing. But the motor has this knock. It sounds between a lower end knock and a tap. Truck has 300,000 on the odometer. I adjusted the timing, it was 1/8 of an inch retarded. Now it's dead on with the stock alignment. Truck runs stronger now but still has that knock. Then I started it, and cracked each injector line open to see if the knocking would change or stop. Still the knock was there. All injectors were getting fuel as well. Truck runs somewhat strong but could be Better. I don't know what to do now, previous owner told me that all 8 injectors were replaced. And they all look new. The far left injector on the passenger side in the very back had air bubbles coming out of it while I was cracking each injector line. Coming out between the injector and the block. Also there is white/grey smoke upon hitting the throttle. I don't know what to do about the knocking now. I was thinking of taking off the injectors and cleaning them out and seeing if that would help. Is it a bad injector pump? I need some help fast. I'm $1200 in the hole if this motor is shot!!

 

It is hard to say without hearing it myself, but from what you describe there is a good chance it is an injector knock. When installing new injectors, if the slightest bit of dirt gets into the injector it can cause them to stick.
I had an injector stick on my 6.9 and was not able to really hear much of a difference in the engine when the injector lines were cracked. If you have access to a pop tester your best bet is to check each injector. I cleaned and re-shimmed my injectors and the engine ran like new, started easier, and gained noticeable power. I used a friends pop tester (he works on Mercedes diesels) and shimmed mine to 2300 psi.
I had several injectors that popped low pressure, and a couple that were leaky when I checked mine. CLEANLINESS IS KEY!! The tiniest bit of dirt will cause problems. I had one injector apart 4 times before it popped correctly.

If you do not have access to a pop tester I would recommend checking at R&D idi performance for a new set.

Do not buy cheap injectors. They are not worth the time. A friend bought pensacola injectors he ended up with 5 different codes and 2 injectors were stanadyne bodies with Delphi tips. We pop tested them and the pressure varied by almost 500 psi.

Edit: I just caught that the bubbles were between the injector body and block. You are going to need new copper washers to seal the injectors. You may be able to seal it by torquing the injector, but if it has been running like that for a while it will have eroded channel through the copper.

 

It also sounds like your timing is off. You cannot adjust using the marks they can vary a great deal. They are primarily there as a reference to start. It may be beneficial to you to have it timed with a timing meter. Most shops do not have the equipment for this so your best bet is to try to find someone locally that may have one that you can use.

 

sounds like a good deal (even if it needs a used idi swapped in.) with it that bad,you may be able to find the bad injector simply by feeling the hard lines.a real bad one will make the hard line much hotter.try that.you can also use a long screwdriver.touch the flat end up against the injector and place your ear on the handle.you'll hear a nice sharp "click" on properly working injector.
it's funny cus i just shared this link,but you can always use your multimeter to find a bad injector too;
https://www.ford-trucks.com/forums/5...he-engine.html

 

You've got a 5-speed, so the injector/rod knock test is easy - Get up to speed, find a nice private long downhill stretch and, with the truck in gear and engine turning ~1600 RPM turn off the key(or even just let up on the accelerator totally). You should either hear the knock go away, or still be there.
If it goes away, it's injectors. If not, it's something else.

That being said, it'll probably keep running either way. According to my local engine rebuilder, these motors will run near forever, getting looser and sloppier all the while.
My truck had a slight knock/tick, and it ran a good 20K before I decided I wanted to rebuild it due to lack of power; it was just fine.
I have another motor with a really bad knocking noise; ran it for a good 1500 miles with no issues(aside from the annoying noise) before I got my newly rebuilt motor for the truck in question... and no, these were not fuel knocks.


Timing wise, advance it a bit. You should be able to play with it and find a nice sweet spot where it has good power and little to no smoke(and the smoke should be black, not gray).
For 'perfect' timing, you need a tool; you can get 'good enough' by ear with some testing.

 

X2, it sounds like a nice truck for the money so even if you have to swap in another motor it'd be worth it and you'd still be money ahead.