Installing a Vacuum Gauge in a Volvo 240

In my quest for fuel economy – and in the interest of having more gauges and fancy lights in my car – I installed a vacuum gauge. Since I drive a car made well prior to the advent of ODB-II I am left out of all the fun electronic things one can plug in that way I must instead resort to old-school mechanical-type things, like a vacuum gauge.

I though I’d document it since the forum people say, essentially, you hook it into the manifold or vacuum line, you can figure it out, it’s not hard. They’re right, but I like photos. So here they are.

First, I found an inexpensive gauge on eBay, which was $16 shipped. I would have also said cheap but it turned out to be fairly well made, with all the necessary parts, and appears to be accurate. Win!

And a note on compression fittings: yes, they just go together like this and you winch them down. I wasn’t sure about it since the tubing slipped out when finger-tightened but wrench it down and it locks and seals fine.

The first (hardest) part was figuring out how to get the vacuum line through the firewall. I finally found a helpful forum post (it was too cold to just go hunt around too much) that mentioned the gasket around the throttle cable. It’s the same one that a couple of the large wiring harnesses go through and (with a bit of poking and prying with a screwdriver) the vacuum hose fit through as well.

While we’re in the engine bay, here’s how it connects to the manifold. The kit came with the handy screw-in fitting and there was an extra hole in the manifold, ready to use.

Here’s where the hose comes through the grommet on the inside, above the gas pedal. The extra tubing is loopy & confusing, but it goes through the grommet on top of those two fat black cable bundles.

From there I ran the tubing over the steering column, through a few other things, and up the trim gap by the door pillar. (Backlight wiring also came up through there.)

My super-fancy mounting bracket also takes advantage of the trim gap between the dash and the door pillar. 1/4″ luan, artfully cut, and a binder clip.

And the finished install (except for backlight wiring). I’ve done the wiring, but haven’t photographed as that taps the dash lighting circuit behind the headlight switch and is impossible to take meaningful photos of.

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