1996 Passat 5th injector disable/removal
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Introduction

The 1996 was the first year for the VW TDI in North America.  There were diesels in previous years but not with the turbo, intercooled, electronically controlled injection pump that distinguishes the TDI from earlier diesels.  It also had a 5th fuel injector unique only to the 1996 Passat TDI.  This 5th fuel injector injects diesel fuel after the turbo exhaust side and before the catalytic converter.  The purpose was to clean the emissions by heating up the cat but it did not work very well and makes the car smoke more.  See 1000q: mk3 jetta and passat differences to see a detailed list of differences, interchangeable parts, model year differences, etc.

The 1996 also had a technical service bulletin (not a recall) that replaces the fuel injectors and ECU (ECM, computer).  Since it was not a recall, it was not done to all 96 TDIs.  It is recommended to remove the 5th fuel injector to reduce smoke and reduce wasted fuel.  There will be little if any increase in emissions since removing the 5th fuel injector will reduce smoke/emissions.

Here are some pictures showing a 1996 and 1997 passat.  The 96 as an extra fuel line branching off to the 5th injector, the 97 does not.  If you follow the extra fuel line in the 96, it goes to a solenoid, then to a fitting on the exhaust.

The 1996 passat line is below left and outlined in red - note the T.  The 1997 passat fuel line is below right - the line has no T.  In the 1997, both lines go directly from the fuel filter to the injection pump.

Parts

1997 passat fuel line to replace the old line.  I recommend an OEM line rather than making your own because of fitment issues.  Do NOT use standard rubber or vinyl hosing because the line will come into contact with diesel fuel and heat.
paper towel to catch any fuel spills
screwdriver
rubber or vinyl gloves to protect your hand from diesel fuel

Procedure

Unscrew the clamps on the old T shaped fuel line and replace with the new fuel line.  If you have a choice, try to get a clear line since it lets you see any bubbles.  I would avoid using a screw, JB weld, or gasket maker to plug the old line here since it gets exposed to fuel.  You do not want any possible source of exposed fuel in the engine bay since this is a fire hazard.

Try to get any fuel that may be in the old fuel lines out.  You could remove the 5th injector, but then you would have to make a plug to seal the old hole and it is probably rusted in place anyways.

Put the new line on and tighten all clamps. Start the car and check for any evidence or presence of fuel leaks, fuel odors or vapors, or abnormal engine performance. 

Below is a picture showing the fitting on the exhaust.  If you want to remove the solenoid and line it won't set a check engine light or make any difference in running.  The issue is that you have to make sure that the fuel line is disabled as mentioned above and that there are no exhaust leaks.  You can weld over the fitting or remove the union and stuff a ball bearing in there and then replace the union over it.

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