How to remove and replace distributor?

Here are the steps to replace/rebuild it but if you are replacing the entire thing then it is easy. You have a choice to either set the engine to TDC on number one and then set the rotor pointing at number one plug terminal on the cap, or just mark where the engine is current set and install the new distributor with the rotor set to that point on the new one and install it.

Another way that you can do this (not the best way because it can cause issues in the future if you forget you did this) is to remove the cap and find out what cylinder the rotor is pointing at on the cap and then just install the distributor and whatever the rotor is pointing at make that the same number the last one was pointing at. So in other words, if you remove the cap as it sits right now and it is pointing at number 3, then just remove it and install the new distributor and where ever that rotor is pointing just make that number 3 and then fill in the plug wires around the cap in the proper firing order. This is not the proper way to do it but for those that have not done this before, it will work.

Let us know if you have questions. Thanks

Hi,

There is a good chance the pick-up coil in the distributor is the problem. The part is really easy to replace. I will provide the directions after this info.

Now, because of the model year, there is nothing in the manuals. So, I have to try and explain what to do. However, before doing anything, turn the key to the run position and confirm there is power on the positive side of the coil. If there is no power, a new distributor won't help. At that point, we will need to go back to the ballast resister and do some checking and after that, the ignition switch.

Now, I attached a pic below to help you visualize what I'm explaining. The easiest thing I can explain is this. Place the timing mark on the crankshaft on top dead center (TDC). Remove the distributor cap and snap a pic of the rotor's position to help you remember.

Next, with the timing mark on TDC, remove the retainer on the bottom of the distributor and remove the distributor.

To install the new one can be a bit tricky. You need to keep the rotor pointing at the same place as the old one, which is at cylinder 1 spark plug wire. If you look at the pic below, I highlighted the plug wire coming from the distributor. The rotor needs to be at that point with the crank pulley at TDC.

Before installing the distributor, make sure there is an o-ring on the bottom. Otherwise, you will have an oil leak. Put a fine film of oil on the new o-ring prior to installing it.

Once the new distributor is correctly positioned, only snug the hold down assembly. It should be snug enough to hold the distributor, but loose enough that you can turn it.

Now you will need a timing light. Based on the one you have, attach it to cylinder 1 and start the engine. Looking down at the crank pulley, you will need to align the timing mark on the pulley with the 12° BTDC (before top dead center) mark on the timing chain cover. When you set the timing, make sure the vacuum advance is not connected and the vacuum hose is plugged going to the engine.

Once set, tighten the distributor, turn the engine off, and restart it. If it starts smoothly, you should be fine If it sounds odd, record the sound and upload it for me to hear. If it is set too far BTDC, it will fight the starter.

Let me know if this helps or if you have other questions. Also, if you have a chance, let me know how it turns out for you.

NOTE: The attached pic shows different styles that could have been used on your vehicle. Regardless of style, still follow the directions I provided.

Take care,

Joe

Hi,

timing won't prevent spark. It will just happen at the wrong time. Also, a voltage regulator wouldn't either. Have you checked the coil? Also, in my previous post, I mentioned the pick-up coil in the distributor. Has that been checked?

With the key in the run position, do you have voltage to the + on the coil itself?

Also, here are directions for testing the coil. The attached pics correlate with the directions.
If you follow these, it will also indicate if the pick up coil is bad.

1978 Dodge Diplomat L6-225 3.7L VIN C 1-bbl
Component Tests and General Diagnostics
Vehicle Powertrain Management Ignition System Pick-Up Coil Testing and Inspection Component Tests and General Diagnostics
COMPONENT TESTS AND GENERAL DIAGNOSTICS
Fig 4 Wiring Harness Test

pic 1

1. Connect an ohmmeter between harness connector cavities numbers 4 and 5. Resistance reading should be 150 to 900 ohms.

Fig 5 Wiring Harness Test

pic 2

2. If reading is not as specified in above step, disconnect distributor dual lead connector and connect ohmmeter between the two leads on distributor side of connector. If resistance is not between 150 and 900 ohms, replace pick-up coil.
3. Connect one ohmmeter lead to a good ground and the other lead to either connector of the distributor. If ohm meter shows a reading, the pickup coil must be replaced.

Let me know. I enjoy working with these vehicles. We'll get it figured out. Just hang in there.

Joe