Come On! I just need a vac line.

[86TSiGuy]

Ok, so I've re-wired my entire alcohol injection system.
All the electrical has been triple checked individually and comes out clean.

My Pressure switch, though it will activate if I blow 2psi into it, will not trip my relay and engage my pump.

Everything check's out so this must be a vac line issue and the switch is not seeing the pressure.

However I've tried three different lines from the manifold. Including the one that feeds my map sensor. Nada...

All I have left are a couple lines from the same common source on the manifold as the others, or try the wastegate can line or one of the lines from the TB.

But that doesn't seem correct. Those lines aren't receiving manifold pressure, the TB one's are getting vacuum force from before the turbo (87' T1 draw-through), and the wastegate line is being bled by the ECU.

So my question is what line would you use to read manifold pressure under boost?

[86TSiGuy]

Okay so I've replaced all my vac lines from the manifold and checked for leaks.
All good there.

But apparently my vac line still won't produce 2psi of posative pressure while the car is under wot.

My question is now this;
Is it possible to have such poor vac response and still have the car run well?
She starts and purrs no other evidence of a vac leak.
Yet the pressure switch can be blown into to create 2psi and trigger it and it still won't trigger under vac signal from the manifold.

[NAJ]

What is your boost gauge showing at WOT?

[86TSiGuy]

Solved (I think)...
The four way split in the common vac tube. (IMHO this is one of the worst engineering concepts I've ever seen) was cracked.
I guess at some point during re-wiring I must have leaned on it or whacked it with a tool handle or something. The crack is real subtle, and doesn't start to leak until positive pressure.

I tore it out and adapted down to normal 1/4" line and then ran tee's for my three lines from there.

I'm going to try again this morning. Last night I was happy to just get it started again.

[detobias]

Quote:

Originally Posted by 86TSiGuy Solved (I think)... The four way split in the common vac tube. (IMHO this is one of the worst engineering concepts I've ever seen) was cracked.

u r correct - a terrible cheap a$$ design ;
marginal when new, and after 20+ years, almost ALWAYS a source of leaks,
and often difficult to find = maddening, as u found

the first "mod" for EVERY TD should be to remove ALL the OE vac lines and replace with a vac block and new lines (dont have to fancy silicone)

u will save yurself a lot of time and frustration, and maybe even save your engine from lean meltdown ..