Engine cranks but will not start!

[EcToCrUsHeR]

Re: Engine cranks but will not start!

Great: you finally got spark. Depending on how you tried to start the beast, you may have fouled the plugs. Pull one, inspect it and clean them if necessary. If they are excessively wet, remove ALL the plugs and crank the engine for a few seconds to clear out any raw gas. You might even try a bit of ether: BUT DON'T OVERDO IT! The coil will give just the spark you need to jump a gap and no more. The spark will appear to be different colors under different light and/or different gaps. The darker the ambient light, the bluer it looks.

Don may be able to tell us if your system has a ballast resistor or not. That could account for the lower than normal voltage at the coil. If it doesn't, I would be paying a lot of attention to your grounds. Often overlooked and a floating ground can cause a myriad of weird issues.

Sorry NetDoc, didn't see your post last night. I'm picking up the boat again from storage today and i'll try both the voltage drop test and of course cleaning and clearing out the raw gas. I know when i pullled the plugs originally when i had the problem, the were all wet. I know my model has the EST ignition so there is no ballast resistor. If worse comes to worse, i'll just re-wired the purple 12ga wires from scratch.

 

[EcToCrUsHeR]

Re: Engine cranks but will not start!

Both. First test the battery voltage. That is base, without that, the other measurements mean nothing.

Then check when the key is in run position, after that do the cranking voltage test on the purple coil wire.

Results from the voltage test:

Original battery voltage 12.35V
Battery voltage run position 12.20V
Purple wire run position 11.5V
Purple wire cranking voltage 7.5-8.25V

I'm thinking the cranking voltage is low...

Also tried cleaning the plugs and cranking with the plugs out to clear out fuel.

 

[NetDoc]

Re: Engine cranks but will not start!

If worse comes to worse, i'll just re-wired the purple 12ga wires from scratch.

BEFORE YOU DO THAT... check your grounds. Be sure that they are 1) clean, 2) tight and 3) existent. Dirty battery terminals are some of the biggest voltage robbers. If you have those temporary ends, simply replace the entire cable or clean and replace the ends. Checking and cleaning (re-terminating) the wiring terminals should be done methodically so you won't miss anything. Start with the battery cables and once you are certain that they are good, retest the voltage drop, but THIS TIME, do it right at the battery and then on the back of the starter. If cleaning them up does not improve your cranking voltage to 9 or 10 volts, I would suspect that your battery or your starter might be the real issue.

 

[EcToCrUsHeR]

Re: Engine cranks but will not start!

BEFORE YOU DO THAT... check your grounds. Be sure that they are 1) clean, 2) tight and 3) existent. Dirty battery terminals are some of the biggest voltage robbers. If you have those temporary ends, simply replace the entire cable or clean and replace the ends. Checking and cleaning (re-terminating) the wiring terminals should be done methodically so you won't miss anything. Start with the battery cables and once you are certain that they are good, retest the voltage drop, but THIS TIME, do it right at the battery and then on the back of the starter. If cleaning them up does not improve your cranking voltage to 9 or 10 volts, I would suspect that your battery or your starter might be the real issue.

I just wanted to add that the reason the boat stopped sparking originally was because the main water hose burst and water was sprayed all over the engine including the distributor cap, coil, and ICM. The plugs are a little melted on the coil and ICM so I'm wondering if that is effecting it also. As soon as i pick up my boat again i will definitely perform a full battery test, clean all the grounds, and recheck all the wiring.

 

[Don S]

Re: Engine cranks but will not start!

The plugs are a little melted on the coil and ICM so I'm wondering if that is effecting it also.

:facepalm:

 

[EcToCrUsHeR]

Re: Engine cranks but will not start!

:facepalm:

I don't mean the spark plugs, i mean the harness connectors on the coil and ICM. Do you think that the ICM maybe got fried? What else besides grounds would cause a low cranking voltage of 7-8 volts?

 

[mikesearay270]

Re: Engine cranks but will not start!

Consider something basic that worked for me. My Merc 470 cranked all day but wouldn't fire, I couldn't get spark. I read to remove the distributor cap and run some fine grit (400-600) on the face of the points to remove carbon build-up. Sounded way to simple but it was the reason my engine would not start. Mine fired immediately after that. I'd sprung for a coil thinking it wasn't putting out enough voltage, when it didn't fix the problem I found the points suggestion and used it. I've been meaning to replace the points but then I have to set the dwell and time the engine but that's beyond my current skill and equipment level.

 

[NetDoc]

Re: Engine cranks but will not start!

I'd sprung for a coil thinking it wasn't putting out enough voltage, when it didn't fix the problem

In automotive, we called this the bucket approach. Rather than learn/diagnose a system, people tend to throw parts at it until something changes. Buying a bucket of parts can be a rather expensive learning experience. It would be better to spend the time and test the individual items. This can be done easily with a DVOM (Digital Volt Ohm Meter). If the points are corroded, they will have resistance when closed. The condenser should have infinite resistance and there should be a lot of resistance between the contacts of the coil as well as between the high tension contact and the frame, but it should not be infinite. Be sure to remove the wires BEFORE you test these things individually. As for grounds and positive voltage contacts, inspect them for corrosion and resistance as well. Sometimes simply cracking a bolt loose and re-tightening, removing and replacing a terminal will restore its integrity. White powdery crap or verdigris (green corrosion) is often a sign of the real culprit. Clean, replace and/or re-terminate as you see fit.