Overview: How to change the distributor cap and rotor on a 1997 Volvo 850 GLT.
This job requires removal of the battery and then the bottom half of the air filter box in order to reach the bottom screw on the distributor cap. Including taking the photos, the whole job of removal and replacement took 2 hours (first time).
1) Common tools: a standard screwdriver for the distributor cap screws and a wrench or socket to disconnect the battery terminals.
Less common tools: You will need a 3mm hex key (pictured below left) for the rotor and a slim ratcheting driver with Torx bit (pictured below right) for the vacuum switch.
2) Remove the battery. (Note you will have to re-type the code for your radio after reconnecting the battery.)
3) Disconnect and remove the flexible air intake tube, seen above. This tube attaches to the bottom half of the airbox and the front of the car near the radiators. It doesn’t have clamps (at least mine doesn’t).
it just pulls off at each end.
4) Disconnect the ignition wire running from the coil to the distributor cap. It is held by two clamps built into the airbox. This will allow the airbox top to be lifted up and out of the way. The wire can be seen in the picture below.
5) Disconnect and remove the two Torx screws holding the vacuum switch to the side of the airbox nearest the distributor cap. It’s a tight fit. Note: there is no need to disconnect the three vacuum hoses from the switch. The picture below is taken from directly above and shows a slim ratchet in place for loosening the two Torx screws.
6) The picture below shows the vacuum switch after unscrewing and removing the two Torx screws. In this picture the electrical cable was disconnected (connector visible at bottom), but after doing the job I realize that it was not necessary.
7) Disconnect the metal clips that hold the top of the airbox in place and remove the bottom half of the airbox from the car. Remove the air filter at this time. Next, remove the bottom half of the airbox. This can be done by pressing down on the two clips at the corners near the engine and lifting up and pushing towards the center of the car. The third pin at the side of the box near the wheel will disengage out of a rubber bushing and allow the bottom half of the airbox to pull out.
The picture below shows the top of the distributor cap (still covered with ignition wires) and the disconnected vacuum switch. With the bottom half of the airbox out of the way, there is now enough room under the top of the airbox to reach the bottom screw holding the distributor cap in place.
9) After unscrewing the distributor cap, label and remove the ignition wires and pull the distributor cap out. I took the precaution of marking the old distributor cap with labels for each ignition wire and used this later to guide installation of the new cap. In the picture below, the cap has been loosened and pulled away and the shield has been lifted out to expose the rotor and the three hex bolts holding it in place.
10) Unscrew the three bolts with a 3mm hex key. After removal, the distributor will look as shown below. Install a new rotor. There is a built-in alignment notch to guide the new rotor into the correct rotary position.
11) Install the shield over the rotor. It has an o-ring near the outer edge and simply fits over the rotor. Then install the new distributor cap. In the picture below you can see the standard screwdriver engaged in the slot of the bottom screw on the new distributor cap. Very poor visibility and access but it can be done!
12) Reattach the ignition wires in the correct order.
13) Reinstall the bottom half of the airbox. Reinstall the air filter. Reattach the airbox clamps.
14) Reattach the vacuum switch.
15) Reattach the flexible air intake tube.
16) Reattach the coil ignition wire to the top of the airbox.
17) Reinstall the battery.
Parts inspection: After doing the job I took a closer look at my old cap and rotor. The date of the rotor was stamped up inside the shaft… it said 96 (my car is a ‘
97 with 113K miles). I figure these are the original cap and rotor. The engine had no misfiring or ignition symptoms, but I figured it was prudent to change these parts.
Cap: Heavy build up on the five edge contacts. Some deposits on the sidewall of the cap. No cracks in the sidewall.
Rotor: some peeling and flaking of the epoxy around the edges of the tip. Some deposits on the metal.