81 Rabbit #3 line issue

[81dubdiesel]

Hey, guys!
New guy to the forum here! Let me start of by telling you a little about myself. My name is Nick and I have been around Volkswagens my whole life. (Mostly air cooled) I got the chance to buy my 1981 Rabbit Diesel LS with 80,000 original miles for a great deal and decided to jump on it. I have had the car for about 6-7 months now and haven't had any huge issues with it until now.

Now to the issues. Starting about 3 months ago I have been breaking my #3 injector line. I have replcaced it three times now. The last time it cracked I knew there must be an issue with something. I read that I'm either missing a bolt on the injector pump, 'missing a bracket or a motor mount is bad, as those are the usual suspects. I compared my car with my buddies 80 diesel L and saw that I am, in fact, missing the bolt on the drivers side of the pump under the injector lines and I'm missing the bracket that holds all 4 lines together. I still have the two up top though. That's the first main issue. The second is that I went to put the new line on my car so I could move it out of the driveway while I waited for my new bracket to come in. I put the line on and now when I rev the car it makes a horrendous knocking noise but it sounds fine at idle. I did some research and found out it is a noise called "nailing." Correct me if I'm wrong. Now my question is what would cause this? The only thing I did was replace the number 3 line. Did some dirt get in the line and maybe clog the injector?

Thanks for your help. I look forward to using this forum and connecting with diesel lovers around the world.

-Nick

[TylerDurden]

Ja, sounds like an injector is fouled. I'd try loosening the injector nuts sequentially and confirming the problem location, then I'd try swapping with another to confirm the issue follows the injector.

If you make/rent/borrow an injector pop-tester, you can check break pressures and spray pattern. Or, take to a shop and pay a couple bucks.

[81dubdiesel]

It's definitely #3 injector. Loosened that line up and gave it a rev and the knock was gone.

[Fatmobile]

You probably got a small piece of stuff in the injector.
I got a piece of paint in one when I was swapping lines and it knocked. I took it apart and cleaned it up, then it worked fine again.

What direction are you counting from? It's usually the #2 injector line that causes grief.
The missing bolt is supposed to have a conical nut that jambs/centers in the bracket. A little harder to find than the bolt.

[82vdub]

The conical device has been missing now from ole 82 for a while. I used a bolt and nut and have been running it this way for about 5 years without any problems.