Trying to help my buddy with his 390.

He drives it once every few months- always runs great.
The last couple of times, he had to really fight to get it started (lacquer thinner, starting fluid, etc). After it started, it ran fine.

The next time he tried- absolutely nothing. The engine will not even sputter.
We've verified a nice fat blue spark (courtesy of a MSD box). The rotor is spinning, so the timing chain isn't broken.

He wants to tear it down, but I think we're missing something simple.

With it not even coughing/sputtering, it seems like an electrical issue, but we've checked that. Could a jumped timing chain do this?

 

Checked the ignition switch? How about the ballast resistor wire - you'll have a nice spark in 'start' (12VDC) but if it's burned out/gone, in 'run' you won't get the 6 -8 VDC to keep it running.

Brain box (ECM) and connections? ( don't know much about the MSD stuff.....same thing?)

Too much play in the timing chain? - check rotor movement with crank movement. Ignition module? The timing OK?

 

May be a loss of compression. Try a Little oil
in the cylinders to bring the compression up a bit.
Not to much or it may foul the plugs. I am thinking
the rigs are stuck from sitting and not ran much.

Do a compression check wet and dry. Cant hurt
and can tell you a lot about your engine.

 

This is what my buddy is thinking. But even if the rings did stick, wouldn't there be enough compression for the motor to cough/sputter/backfire...anything at all?

i mean- this thing is DEAD. no signs of life whatsoever.

 

The cylinders may be washed down from the use of starting fluid.
And it may well not even fire on start fluid if this is the case.
Just try a little oil down the plug holes and it may start right up
Better yet do a compression check and know for sure.

 

Very possible a worn timing chain/gears could jump. Turn the engine over by hand until the timing mark lines up on the compression stroke of #1 cylinder, then check the position of the rotor to see if it is pointing to the #1 on the cap.

 

Many years ago I had a guy at work who drove a 80's full size Bronco and that happened to him. Ended up having to do a ring job. I was blown away at that as I had never heard of it happening before....

 

I would think you'd get a fart out of at least one cylinder.....What do the plugs look like?
Try the 'ol finger compression test as suggested...you said you have spark.....fuel? Compression test/leak down. Have many mice ( meeses?) gnawing away at the electrical lines? Corrosion on the +/- battery and starter?

 

Is the fat blue spark coming from the coil wire or spark plug wires?

 

Don't think for a minute that the MSD box is good.......just because you are getting spark because it is a multi-discharge unit it can fail under load

 

With nothing was said about the mileage on the engine, so with it having spark and gas I'd do what hiball3985 said ^^^