proper order of engine analysis

47topless

47topless

Well-known member
My recently purchased 1947 Ford, with stock V8, is not running very well. It starts immediately but seems confused under load. The only thing I have done is change the spark plugs. There was some improvement, but just a little.
Is there a proper "order of elimination" when diagnosing a poor running engine?
Should I start with a compression test to establish a baseline?
Thank you.
Phil
 
Vacuum gauge IMO to start with
 

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Check the vacuum advance unit for integrity. Not necessarily the proper order of troubleshooting, but that was the cause of a similar issue on my recently acquired '50.
 
I would start with a compression test, since you seem to be able to handle that yourself. The ignition? Unless you have the tools and experience in working with these, it is best to send it out someplace to have it checked, repaired (if necessary), and the timing set. Also, you can do a simple check by looking down the carburetor and see if it has a healthy squirt of gas from the accelerator discharge nozzles. There can be many things that can go wrong with these carburetors (leaky needle, leaking power valve, bad float setting, just plain dirty etc.). If you have the skill, you can go through the carburetor yourself, if not there are guys out there that are wizards with these and won't break the bank. A compression test would be a good first step, if only to ensure that there are no serious problems with the engine.
 
I would suggest that some description of the problem in more understandable terms might help in suggestions of troubleshooting.

It seeming confused is too woolly a description.
 
Thank you all for your responses. I guess there is no set order, for the process of elimination, in diagnosing a poor running engine, but a great starting point is a vacuum test. A compression test will provide some useful clues as well. Tools for solving the mystery of a stuttering engine.
Please stay tuned.
Thanks again,
Phil
 
Phil, when doing the compression test, hold the throttle plate open
on the carb so some air can be sucked into the cylinders to give you
the best chance at getting an accurate compression reading. ;)





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Phil, do you have another car with similar components? It is sometimes a reasonable thing to do to swap some components to see if the problem goes away.

I had a problem where the car would misfire while accelerating. It would get progressively worse until it wouldn't go at all. It would drive when cooled down.

In my case it was a bad distributor cap one time and a bad rotor arm another. So if your stuttering falls into the getting steadily worse category, it may be like that.

You might try a known good condenser that works well in another car.
You might try cleaning the points. (Easier with distributor off)

Not sure what a compression test will tell you but no harm in doing it.

Let us know what you find.
 
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