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Re: [T3] 72 square, rough idle, #1 missing?

On 6 Mar 2002, at 11:31, Drake . wrote:

> This is a re-do of my first post to the T3 list, looks like my original 
> message didnt get through from my home account for some reason.

You're right, I don't think we've seen this message before, but this one came 
thru just fine.

> I have a (just purchased for my wife) '72 squareback (FI, M/T) that I have 
> just finished installing a rebuilt longblock. Also installled points, 
> condenser, cap, rotor, plugs, plug wires, clutch.
> The car runs rough, especially at idle. When accelerating, its seems to 
> smooth out. The motor does not decel quickly either, though since this is my 
> first T3, much less one with FI I dont know if this is the norm or not.

> First issue: I have set the timing, however in the manual it states to pull 
> the vacuum retard hose off the dist etc. When I pull the hose off there is 
> no change in idle, nor can I feel any vacuum in the hose. The hose is 
> connected via a "tee" to the air distribution manifold at a 1/4" port on the 
> left side. I can not feel any vacuum there either. I squirted some Chemtool 
> in the port, and saw that it did get into the throttle body. The other side 
> of the "tee" goes to a valve? (I dont have my manual in front of me so I am 
> not sure of the appropriate name) next to the air pressure sensor on the 
> left side of the engine compartment. This device has to larger ports on it 
> as well, one connects to the air cleaner. I am not sure at the moment where 
> the other goes.

Do you have the Bentley manual? This is the only manual that I know of that 
covers the timing of the unique 72 correctly. The original vacuum hoses are 
complicated. There should be 2 hoses to the dist. The green one is the 
retard, is slightly larger, and is connected to the side of the vacuum can that 
faces the distributor.

Is this what you have? I think the retard hose should go directly to the intake 
air dist., no Tees or valves. There may be a diagram in the Bentley 
somewhere, or check the owner's manual if you have it. The advance hose 
should go to that valve on the left side of the engine, although that valve can 
be bypassed to simplify things.

> Second Issue: I have pulled the plug wires one by one with the engine 
> running. #1 no discernable change, #2 and #3 seem to be firing correctly, #4 
> there is a small change. I then proceeded to the fuel injector plugs, same 
> results as with the plug wires. This lead me to beleive that I had a plugged 
> #1 injector, or something with the injector circuit for #1 and #4. I then 
> pulled injectors #1 and #2, and with the key on (after adjusting the 
> throttle switch) opened the throttle. I visually observed #1 squirting fuel, 
> so its not plugged.

All you really know is that #1 & 4 are weak, but don't fall into the trap of 
assuming that the fault MUST BE with the fuel system. There are THREE 
possibilities: fuel, spark, compression. You can verify spark by the use of an 
inductive timing light around THAT SP wire, but that is only certain if the SPs 
are known good and the wire/connector are good also. 

> As a side note here, I repeatedly opened the throttle while having only one 
> injector plugged in at a time, and for some reason only #1 and #3 fire. 
> Injectors #2 and #4 will fire if I plug the wires for #1 and #3 into them. 
> Since this is the accelerator pump function, I would have thought that all 4 
> injectors should fire during this operation. Is this the case?

1 & 4 fire together when the distributor is in one position, then 2 & 3 fire 
together in the other half of the dist rotation. Others here have reported that 
there is an intermediate position where NO injectors fire.

> I then checked continuity of the injector breaker points in the dist. Middle 
> to one side checked good, then had my wife bump the engine around until I 
> got continuity on the other connector.

Did the resistance come down to near zero (less than 5 Ohms?)

> I then re-assembled everything and started up the engine again to realign my 
> brain with the problem :) Again pulling #1 off the dist cause no real 
> difference in the way the engine runs. #4 is questionable, but idle does 
> pickup when the wire is plugged back in. I also swapped the plug wires for 
> #1 and #2 to verify the wire, its good. This evening I will be checking all 
> of the valves, performing a compressions test, and ensuring that there is 
> spark through the plug on #1.

The spark and compression tests are the right next steps. You have normal 
gap (.027-.028") on the SPs?

Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA

List info at http://www.vwtype3.org/list or mailto:help@vwtype3.org

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