[T3] Vacuum Leak

[Adriel Rowley]

----------------------------------------
> From: jadney at vwtype3.org
> To: type3 at vwtype3.org
> Date: Sat, 8 Jan 2011 21:25:50 -0600
> Subject: Re: [T3] Vacuum Leak
>
> On 8 Jan 2011 at 18:02, Adriel Rowley wrote:
>
> > > From: jadney at vwtype3.org
>
> > > I've not seen good results from rebuilt injectors. My impression is
> > > that they don't always meter out the correct amount of fuel. New or
> > > used bosch 007s are what you want. Keep in mind that if the plug is
> > > fouling, the problem may not be too much gas, it may be too little
> > > compression or too much oil leaking past the rings.
> > >
> > Well, will see if that is the case.  Bob's test should show this, and if
> > the injector is not spraying what appears to be the same, might have a
> > spare injector.  There are no knew ones, as far as I know.  Oh, and the
> > rebuild is for the seals and maybe the valve; the windings are still the
> > same.
>
> I don't think you can tell much from the appearance of the spray. If
> it looks bad, then it IS bad, but if it looks good, then it may still
> be bad. A good looking spray cone can still contain 50% too much or
> too little gas.
>
I will check around and see if my egg donor has a measuring cup: that way I 
can measure out put.

> > Well, will see if that is the case.  Bob's test should show this, and if
> > the injector is not spraying what appears to be the same, might have a
> > spare injector.  There are no knew ones, as far as I know.  Oh, and the
> > rebuild is for the seals and maybe the valve; the windings are still the
> > same.
>
> If some of your injectors have been rebuilt, then I would be
> suspicious of them. I've fixed cars that ran poorly just by replacing
> "rebuilt" injectors with correct Bosch injectors. I have a suspicion
> that in the rebuild process the rebuilders are not always careful
> about which nozzles they install in which injectors. Bosch made
> different injectors for a reason.
>
Yes, I understand where you are coming from, just not FULLY convinced. ;)  
She did run alright with them on the last engine.

> > > I also install the seal on the nose of the injector first. Then you
> > > have to make sure that it seats nicely in the manifold when you
> > > install it.
>
> > How?  Not real easy, especially with the fuel line fighting one the
> > whole way.  The F.I. hose seems to be stiffer than the other low
> > pressure fuel hose (F.I. hose not my doing nor approved, especially
> > considering it is 7mm).
>
> Use 5/16" fuel line and don't try to connect all the hoses before you
> insert the injectors (assuming you have it all apart at that point.)
> If you've just pulled them out to check the spray pattern, then the
> hose should not be fighting you if you're just putting it back where
> it came from.
>
I do not disconnect the hoses: too much to bother with, and stresses the 
rubber.  What I mean is the hose assembly wants to go in any place but 
where the injectors need to be: get the injectors in place, then the hoses 
relax and pull the injectors out of the runners.  Now that I think on it,
just might be the hoses are a tad short.  Guess this is why we need to 
think things with others. ;)

As for 5/16" fuel line, that is what I use, when I need to replace the hose.
So far, the 7mm is still good, so why replace it when it was so expensive in 
the first place? ;)

> > > > Where is the vacuum leak?
> > >
> > > ??? You're the one who reported finding it. You tell us.
> > >
> > What I mean is, you say it is not the injector seal, so what else could
> > it be?  The spray was general, so only know what general area, and I am
> > under the impression stock F.I. gaskets do not leak.  That seems to
> > eliminate the possibilities...
>
> I don't think there is a vacuum leak. Any gasket CAN leak if it's not
> installed properly. Surfaces have to be clean and nuts have to be
> tight, etc.
>
Then why did the ether gas change R.P.M.?

Will check cleanliness, as sometimes that is an issue of mine, especially
considering where the final assembly took place. ;)

> The most common place for leaks is at the joints between the IAD and
> the intake runners. Those can usually be cured by loosening all THREE
> parts and letting them find their own best position. This can be
> difficult if the connecting hoses have already been bent and
> distorted. I sometimes have to straighten intake runners that have
> been bent out of parallel and rotate hoses which have an offset to
> them due to being installed poorly before I got to them.
>
Remember I made the mistake of using R.T.V. at the I.A.D. and the 
runners?  I did check those for leaks, and they are good.  I see now 
how if the runner is pulled short, it could cause the runner to not sit 
proper on the head.

> OTOH, leaks at those joints are rather unimportant, because they
> basically leak right into the IAD, where the pressure is measured, so
> a leak there is very little different from opening the throttle
> slightly more. It might make a noticable difference at idle, but
> nowhere else.
>
I cannot go below 1200R.P.M. despite everything to lean it out and 
starve it.  Makes it not the most fun to drive, as the shift points are 
off.

> But start by checking the compression on the cylinder that is
> fouling.
>
I will check the two, and see how they compare, especially since this
is a new engine.


Thank you so very much!
Adriel