QuestionHi Howard,
This engine was running a couple of weeks ago, I was attending some other repairs, then decided to tune up the engine. Now remember this was running a few weeks ago. Car is on jack stands so did not go anywhere. I bought and replaced Dist cap, rotor, wires and plugs. After installed it would not run, would not even try to run. I put old parts back on and got same results. I checked the timing while cranking engine and timing is OK. I smell gas when I remove plugs so am assuming the engine is getting gas. I tried starter fluid but nothing. I am at a loss at what to try or why this happened. I am getting spark as the timing light works (and felt it with my finger by mistake) Any ideas?
AnswerHi Steve,
You need to remember when you have an engine that don't run that there are only three items that make an engine run. Compression, Fire and Fuel, with conditions on each.
While working in dealerships for most of four decades, I learned to block out of my mind what it might be that makes an engine not run and think first in which of the three sections the problem is in. Then run a few simple tests to show which section it is in.
The tests of the systems MUST be done in order and never vary from that order.
First is compression and just because it was good just before it would not run means nothing because every part was good just before it fails.
Run a compression test first and with the throttle OPEN. You should see 125 PSI to 170 PSI on each cylinder with little difference between cylinders. If you don't have that don't waste you time looking any further until that is corrected. And don't skip it.
Second it Fire (Ignition) and I didn't hear the tests I have to run on ignition. I often had a scope to test ignition but most people don't have access to that kind of equipment but there are other ways to test ignition. Here is a simple test that does not require any tools except a plug wrench.
Remove #1 plug and connect it to the plug wire and lay the plug on a metal part of the engine.
Now, place your thumb over the plug hole and have someone spin the starter and watch the plug spark. Each time the piston comes up on compression it will blow your thumb off of the plug hole with a "Pop" sound. At the same time the plug will spark like a "Click" sound. If it looks like the "Pop" is causing the "Click" it is close enough to being in time on that cylinder that it will run. Now, do each cylinder the same way which confirms that the firing order is correct for that engine. If you hear a "Pop- Click" or a "Click-Pop" it may be out far enough not to run. (This is a rough confirm of the firing at about the correct time but does confirm that it is firing on the compression stroke and not on the exhaust stroke as a timing light might show.
You need to note the thickness of the spark and color (not in bright sunlight) It should be thick as a pencil lead and blue in color. If it is thin as a hair and orange or yellow it is a weak spark and may not start the engine.
If BOTH of these tests have been run as I indicated then and only then can you test fuel.
This one is simple. Just spray starting fluid into the intake while trying to start the engine. If it does not start on starting fluid then you didn't do the first two system tests I outlined. If it does start on starting fluid but will not keep running unless you keep spraying starter fluid into the intake then you have a fuel problem and that requires another set of tests. Let me know and I will cover them.
Don't skip anything I covered and you can NOT fail to find the problem.
Howard
