How to replace an engine distributor
An engine distributor is the key component of a vehicle’s ignition system. Most vehicles manufactured prior to 1985 have standard mechanically controlled distributors. Many later model-year vehicles are equipped with computer-controlled distributors, or in some cases, crankshaft-triggered distributor-less ignition systems. These later designs are highly integrated into the engine’s computer-controlled management system, and there is very little a do-it-yourselfer can do with them.
If you are the owner of an older vehicle and are interested in improving the performance and reliability of your engine, you should consider replacing your current engine distributor with a new or rebuilt unit. This DIY article will take you through the steps of replacing a standard, non-computer-controlled distributor with an electronically triggered (points-less) distributor. (Rebuilding your distributor is an advanced project that requires specialized tools; it is beyond the scope of this DIY project.)
Park your vehicle inside the garage or outside in a well-lighted level area. Locate the distributor under the hood in the engine compartment. Here are some hints on what to look for:
- The distributor has a plastic cap with the spark plug wires coming out of it (there should be one wire for each cylinder of the engine).
- It also has a center wire that goes to the ignition coil, which is a metal can-shaped component about 2-3 inches in diameter and about 6 inches tall.
- Most distributors are located on the top of V6 and V8 engines, and are to one side of inline four- and six-cylinder engines.
You may also want to check your owner’s manual, since there is likely to be a diagram of the engine compartment noting the placement of the distributor.
Once you have located your car’s distributor, take a good look at how it is attached to the engine. There should be a clamp with a bolt or screw that prevents the distributor from rotating. This bolt may also hold the distributor to the engine, or there may be a separate set of bolts that hold the distributor to the engine. Make sure that you can reach these bolts with either socket or combination wrenches.
To perform this DIY project, you will need to use a timing light to set the timing of your engine once the new/rebuilt distributor is installed. In order to do that, you must find the timing specifications/instructions that are specific to your vehicle. For most newer vehicles, these specs are on a sticker located in the engine compartment. You can also check in a repair manual or go to several online sources for your vehicle. Follow the instructions that come with the timing light, and practice finding the timing mark as specified for your vehicle.
Point of no return
If you cannot find these specifications or you cannot locate the timing marks with a timing light, you cannot perform this project. Take your vehicle to a trusted technician to perform this distributor replacement.
- Combination wrenches
- Socket wrenches (generally 3/8- to 3/4-inch)
- Timing light
- Flat-bladed and Phillips screwdrivers
- Allen keys
- Rebuilt or new electronically triggered distributor, and a new cap and rotor (if not supplied with the distributor). These should be available at your vehicle’s dealership or, for popular models, at auto parts stores. Older vehicles may have specific online sources for rebuilt distributors.
- Repair manual or other source for ignition specifications for your vehicle
If they have not been replaced recently, it may be wise to change the spark plug wires at this time.
Note: Your purchase of an electronically triggered distributor eliminates the points assembly in your distributor, so you do not have to deal with dwell adjustment or setting points.
Park your car (inside the garage or outside) with plenty of space to work around each side of the engine compartment.
- Step 1: Disconnect the distributor cap from the distributor. The cap may be held in place with clamps that can be removed by hand, or you may need some basic hand tools. For example, some caps are held in place with screws. Note that many older GM vehicles have a screw fastener that only requires a quarter turn of the screwdriver to release the cap.
- Step 2: Make a diagram of where all of the electrical wires are located, and mark the wires using masking tape so that you can replace them in the same location on the new distributor.
- Step 3: Remove all electrical wires that are attached to the distributor.
- Step 4: Before removing the old distributor, you will need to scribe two marks, which will help you install the new distributor with the same orientation. One mark should be made to match the distributor housing (outside body) to the engine mounting point. Pick a point on the outside of the distributor housing that is accessible and that you can reproduce (in the same spot) on the new distributor. The second mark should be made on the inside of the distributor housing to indicate the position of the rotor within the distributor. Think of the rotor as the hour hand of a clock. The rotor on the new distributor will need to be in the same position when you install it. This is important because if you do not mark these points properly, you probably will not be able to start the engine with the new distributor installed.
- Step 5: Take the new distributor out of the box and mark the outside housing in the same place as on the old distributor. In addition, try to orient the rotor in the same position. Take a good look at the housing and shaft components that will not be visible when the distributor is in place. Note that the distributor shaft is rotated via a gear or slot at the end of the shaft. You will need to install this shaft aligned in the exact same way as the old unit. A little time and patience now will make things much easier when you go to start the engine!
- Step 6: Remove the bolts or screws that hold the distributor housing to the engine. Now gently pull the distributor housing out of the engine. Look carefully at the rotor, since its position may rotate as you pull the distributor out. This is normal. If the rotor arm rotates slightly while you are pulling out the old distributor, note the final position of the rotor and use it as your starting point when you install the new distributor. In other words, the installed distributor must place the rotor in the same location as you marked in step 4. Be as precise as possible with this.
- Step 7: Transfer your marks from the old unit to the new replacement distributor. Install the new distributor on the engine, making sure that the distributor rotor and housing are in the same location as the old unit.
- Step 8: Re-install the fasteners that hold the distributor to the engine. Do not fully tighten these yet; snug them down until you cannot rotate the distributor and then loosen them just enough so you can rotate the distributor by hand with a little bit of effort. Again, make sure that all the marks are re-aligned (or if specific instructions are supplied with the new distributor, follow them).
- Step 9: Reconnect all of the electrical wires as noted in your diagram, and replace the distributor cap and spark plug wires.
- Step 10: Now comes the proof of the pudding! Double-check all the connections and start the engine. If the engine will not start but sounds like it wants to, rotate the distributor away from your mark a small amount (just the width of your mark) and try to start the engine again. If it seems to have a harder time starting, rotate the distributor in the opposite direction, again slightly past the original mark. If the engine sounds like it wants to start but still will not catch, continue slight rotations of the distributor until the engine starts and runs.
- Step 11: Once the engine is running, let it warm up enough that it will idle smoothly. Then stop the engine and put a timing light on the No. 1 spark plug. Restart the engine.
- Step 12: Use the timing light and set the timing by following the instructions that are specific to your vehicle. You adjust the timing mark by rotating the distributor housing by very small amounts. When you have adjusted the timing to the correct mark, tighten the distributor clamp fasteners.
- Step 13: Take the vehicle out for a test drive. Make note of the vehicle’s response under acceleration and varying engine loads. You may be pleasantly surprised at the improvement.
Clean and return all of your tools to their appropriate places. Return the old engine distributor to the auto parts store if there is a core refund, or dispose of it properly.