QuestionQUESTION: I am getting a very weak spark. The coil has been replaced. I have 12
volts on the + terminal while it is running. Points are gapped at .016". It
will idle but when you give it gas, it wants to die. It acts like it is missing.
I think they are all missing because of the weak spark. If you pull one of
the plug wires it doesn't idle much different. The plugs have been
changed. The original plugs looked good, but all four where black.
ANSWER: Hi Curtis,
You have several items wrong that you told me. First the voltage test of the (+) side of the coil while running is a useless test. (if the wiring is original) The power comes through a resistor wire but can only be tested when not running and the negative side of the coil must be grounded when you do a voltage test on the positive side of the coil. This should show about 6 or 7 volts. All that will tell you is that the resistor is in the system. Nothing else.
How did you determine you had weak spark? "Pull one of the plug wires and it doesn't run much different"????? A "cylinder kill test" is done at idle by killing each cylinder one at a time AT IDLE and note the RPM change. They all should drop RPM about the same. This only tests to see if each cylinder is pulling it's own load. It don't tell you what is wrong.
Black plugs does tell you a little. Glossy black is a fouled plug (oil or electrical ????) Flat black is a over rich mixture (too much fuel per air)
You said "point gap" meaning this car has been modified to a pointed distributor? If so, did you replace the condenser? This car came with an electronic ignition.
When I worked in dealerships I often received cars with these kind of complaints. I had to disregard everything above and start from scratch and run the normal tests.
Compression test first, (IF And only IF) it is ok I can then proceed to set ignition timing and clean or replace the plugs. After that I can look at the carburetor. Remove the top off of the top pot and examine the diaphragm for holes or tears. If that is ok I check the needle to see that it is not damaged in any way and confirm the correct oil level in the top of the carb.
Do this, put a timing light on the coil wire not a plug wire like you are setting timing and hold the trigger down and look at the flash and rev the engine up and watch the flash to see if there are any signs of blinking. Even a slight miss fire will show.
Let me know,
Howard
---------- FOLLOW-UP ----------
QUESTION: Howard,
Thank you for your reply. Just to clarify a few things. I was checking the spark by unplugging each spark plug wire and putting it next to a ground. Instead of a strong orange spark that you can hear cracking, it was hardly visable let alone able to hear it crack.
The black spark plugs are more of a powder black or flat black.
I did find out that this is not the original engine. That's where the pointed distributor comes in. How important do you think it is that I find out what year this engine is? Can I find this out by a number on the engine?
I will be performing the tests as you have mentioned in your first response, but I don't see a point in looking at the carburator until I solve the mistery of the weak spark. The condensor has not been changed so I will be looking at that and other parts of the distrubor. The cap, points and rotor look new but I don't know if they are the correct parts. I should probably us the distributor number to get the corrects parts. This is a car that I just got (free and in great shape) from a lady that hasn't driven it in a year. It was parked at her mechanics garage for quit some time. I have already pulled the fuel tank and dumped the old fuel so I could start fresh. For some reason when I got the car, the points were set at approx 0.030". ??? I reset the points at 0.016" and advanced the timing to where it feels like it should run. I will put a timing light on it in the up coming days and perform the checks that you suggested.
Thanks,
Curtis
AnswerPowder black is Flat black and is excess fuel per amount of air (rich mixture)
You should only use the color of the spark as an indicator if you look at it inside of in a well shaded area, not out in bright light. A thick blue spark is a strong spark and an orange or yellow thin wire spark is usually a weak spark. The only way to be sure is to put it on a scope to see what the spark really is.
Sometimes the engine number can tell what year the engine was and sometimes not as the block could have been changed. Many different year distributors could be installed and often were because of faulty electronic ignition systems.
Howard
