1986 240 DL Ignition control module vacuum hose

[mhgreen]

Hello all.

B230f, Automatic trans

There is a vacuum hose that goes from the ignition control module to the intake manifold. At the intake manifold the vacuum hose connects onto a nipple on a bolt that screws into the manifold. At the ignition control module, the hose connects to a nipple on the bottom part of the module facing the front of the car. What is the function of this vacuum connection?


Matt

[lummert]

Vacuum controlled timing advance?

[mhgreen]

Vacuum controlled timing advance?

I'll have to research this unless you'd be willing to explain.

[93Regina]

Vacuum controlled timing advance?

....willing to explain.

As the engine increases in RPM, for a given load, the timing must be advanced since it takes so long for combustion to ignite. If timing is advanced too much, denotation will happen; if timing is decreased, less power and less mpg.

It takes a timing light to evaluate if advance is working or not, and iirc, the vacuum timing advance will not start working until after 1,000. There is also a "mechanical advance" as based upon engine's RPM.

So, timing advance is part RPM based, and part vacuum based on your Volvo.

Here's what a LH 2.2 curve looks like

[93Regina]

Taking a look at LH 2.2 ignition curves

[mhgreen]

Good information. Just trying to learn what everything is. Thanks for the guidance


Matt