a 1985 2l-t vacuum question

[roversnomore]

hello all, i and reviving a rwd 85 turbo diesel. does anyone know why there is a vacuum line running to the injection pump? there is a the boost sensor and below that is a vacuum line, seemingly to the other side of the diaphragm... any ideas?

thanks.

 

[gnob]

my 3l uses it for AC idle bump

 

[roversnomore]

my 2l-t does not have the high idle system. i wonder if it is a high altitude compensation.

 

[gnob]

there's a fsm in resources. you could dig through there

 

[roversnomore]

yeah, i have done that and found no description. i will keep looking. thanks for the help.

 

[gnob]

...

 

[Eurasiaoverland]

A photo of what you are trying to describe would be helpful.

 

[roversnomore]

i will take a picture and maybe a video tomorrow.

for now, here is a diagram. you can see the vacuum line coming from the vacuum pump to the HAC and on to the injection pump.

 

[Eurasiaoverland]

It seems for CA emissions the engine has both a boost compensator on the injection pump, and a high altitude compensator. I have never seen this before, but I assume it is to adjust off-boost fuelling at altitude. I am not sure why it seems to be linked to the EGR via a BVSV (bimetallic vacuum switching valve).

So you have a line from the intake manifold to increase fuelling on boost, and a line from the HAC to the other side of the boost compensator to reduce fuelling off boost at altitude.

Interested to see a picture of this.

 

[roversnomore]

this tracks, there is an entry in my FSM stating that "The HAC valve maintains vacuum from the vacuum pump at a consistent value in spite of atmospheric pressure change. "

here is a picture of my current plumbing.
i have removed my EGR system as the EVRV ecu-cotrolled valve was chewed up by mice.

 

[roversnomore]

and sadly, there is a metallic tapping sound that I don't think belongs...