silly vacuum question

[1990LTD]

What is over near the battery that draws manifold vacuum? It's actually really close to the battery.


The vac line goes in to what looks like some kind of solenoid that has two other sets of wires running to it. It's dark or else I'd take a picture of it but I wouldn't imagine there's much over there drawing vacuum?

[87gtVIC]

Charcoal canister?

[91waggin]

Charcoal canister holds fuel vapors under the battery. ECM opens solenoid, and engine draws fuel vapor from the canister into the intake. If it works, leave it alone.

[1990LTD]

In my haste (well, I haven't slept in a couple of days) I reinstalled everything, hooked everything back up...except the charcoal canister and a curious device with one vac port and one wire harness, sitting up on my firewall. Went to start the car.....nothin. Hooked up the thing up on the firewall and the car works dandy. After that I noticed that I forgot about the charcoal canister too

[91waggin]

and a curious device with one vac port and one wire harness, sitting up on my firewall.

That would be your MAP sensor. VEERY important to the fuel injection system if you don't have Mass Air.

[1990LTD]

That would be your MAP sensor. VEERY important to the fuel injection system if you don't have Mass Air.

yeah without that guy it would start, rev, die. start, rev, die.

[gadget73]

yeah it won't go without the MAP. If you ever want to see how funky it can run, pull that vacuum hose off the MAP while the motor is running. It does interesting things.

[1990LTD]

i'll bet. it ran pretty strangely when i had the map unplugged and gave it gas to start it. i don't really know how to describe it

[1990LTD]

what will disconnecting that line to the charcoal canister do? is it the type of thing that just won't run if it has no vacuum?

[86VickyLX]

For one, vacuum leaks, two, you'll smell gas vapors, 3 the computer won't allow these vapors to be pulled into the engine, causing it to use more fuel via injectors.

[91waggin]

^^^what he said

[1990LTD]

I plugged the vac line and stuck the end of the existing one coming off of the canister into one of the screw holes in the fender so it's venting outside the engine bay. I'll get some new hose and hook it back up soon.