Problems Starting Warm Engine - Suggestions?

[88 Supra Comp]

Having problems starting my engine when it is warmed-up.

Have an 88 Supra Comp with Ford 351, has the following:

MSD Ignitioin, Petronix Coil, Edelbrock 600 CFM Carb, Holly Electric Fuel Pump, Bosch Starter, Plugs & Wires.

Starts like a champ when it is cold......needs to warm up for a couple of minutes, then idles great. Problem is once you for a while and shut her off, she starts really hard. Then yesterday....I was running at kneeboard speed with the kids for a while, backed off plane, and she died and would not start at all. Ended up getting towed in, and then while waiting on my friend to get the trailer (had been about 25 minutes) tried to start at the dock, and started fine???

Talked to a local inboard dealer and they said thought that it was the electric choke that may be out of adjustment. Told me when hot to turn the key on for about 25 - 30 seconds then try to start, said the electric choke would then open up???? Have not tried this yet, but have no idea if this would be it?

Another friend said it may be vapor locking......but the dealer said engines should not vapor lock unless over 200 degrees.

Anyone have any thoughts/advice??? Supposed to leave for Lake Cumberland, KY next week, and am now worried how it will run?

[Salty87]

can you elaborate on starts really hard....wouldn't start at all...

the starter was spinning? clicks from solenoid?

do you have a voltmeter? have you checked your cables/connections? ever notice any of them getting really hot when it won't start?

how old is the coil?

one more...last time you checked the timing?

[DKJBama92Mariah]

Just to clarify your staring problem. Is your starter having a problem turning the motor over, or is it kicking it over good, but the engine just isnt firing.

How long to you leave it off before restarting? The electric choke uses a heated coil element to open. It is energized whenever the ignition is on. Once you cut off the boat, it will take several minutes for it to cool down and close the choke.

I have two guesses for the culprit:

(1) The engine could be flooding with fuel. This happened to me the other day. Its the only time it has ever happened so it caught me off guard. It happened after about a 15 minute run at high cruising speed. The boat sat about 20 mins and wouldnt crank. If this is the case, DONT pump the throttle, it will only make matters worse. Pull the knob on the morse throttle out to put the boat in neutral. Move the throttle ALL the way back to wide open throttle, hold it there, and then crank the engine over. This will clear the excess fuel from the cylinders and the boat should fire within 10 seconds or so if this is the problem.

(2) If its not fuel, then its gotta be a spark problem. It can get pretty hot under the engine hatch and cause some problems. Electrical resistance increases as temperature increases. If you have a weak component anywhere in the ignition system, this increase in resistance could be just enough to keep you from getting a spark. I would take a voltmeter and check the voltage at the coil lead wire.

WARNING: I hope all these electrical components you have (MSD, Coil, Fuel pump, starter) are marine grade units. Marine parts are different in that they are shielded so they do not produce sparks that could ignite fuel vapors. Its not worth saving a few bucks to risk turning your boat into hiroshima and risking death or injury to your loved ones. Also, if you do have a fire and your insurance company finds out you had non-USCG approved parts on the boat, they will deny the claim. The reason i ask is that i have not heard of a MSD marine ignition. If the stuff is not marine grade; replace it with proper parts, end of story. I would suggest an electronic igntion distributor and coil from discount inboard marine at www.skidim.com.

On the other hand, if the starter is having trouble turning to motor over, then you most definitely have a heat-soak issue in your starting system. If the started or solenoid are worn, and they get hot enough; they just dont have the power to kick the motor over.

Good luck and reply back with some more specifics and maybe we can help track this thing down.

Cheers,
DKJ

[88 Supra Comp]

Wow, thanks for all the respones. Let me see if I can add more clarification:

I'll have to check on the Marine MSD, I thought it was, but you raise a good point.

For the problem.......it turns over fine....starter is new, and spins it withouut fail...just no spark.

It starts hard after hot unless off for probably 1/2 hour or more, was off for about about 20 - 25 minutes yesterday while getting towed in, and although started at doc, was hard to start.

I tried a combination of throttle positions.......both pumping, and about 1/2 throttle. Did not try wide open. (Also does it matter which direction wide open, ie....forrward direction, or reverse direction? Obviously with the "button" out in neutral position it will only go "so far" forward till throttle bar hits button)

My concern was that as much as I cranked.....I never really smelled fule, like it was being flooded.

As for other parts......pretty sure the carb is marine, and thought the fuel pump is as well, but will check.

Thanks to all for help!

[DKJBama92Mariah]

To clear a flood, push the throttle all the way BACK.

It sounds kind of like vapor lock, but it just doesnt "feel" like it. See this tech article on a landrover site. http://www.landroverclub.net/Club/HTML/SIII_vaporlock.htm

Since you have an electric fuel pump, vapor lock should not be much of a problem b/c the pump creates positive pressure thus increasing the boiling point of the fuel. As opposed to a mechanical fuel pump which is "sucking" fuel from the tank to the engine creating negative pressure. There is a way to check for vapor lock. When you are experiencing the condition, pull the flame arrestor off the carb and look down the throat. Have an assisstant pump the throttle all the way ot wide open once without cranking the engine. You should see and hear some fuel squirt into the carb throat from the accellerator pump in the carb. If no fuel comes out, then the carb isnt getting any gas and i would suspect vapor lock.

Just out of curiosity, how is the electirc fuel pump hooked up to a carb? Is there a return line running back to the tank to get rid of the excess fuel? I'm just not really familiar with electric fuel pumps on carb applications.

Now... We still have the two more potential causes: flooding and lack of spark.

When you cut the engine when it is hot. The evaporating fuel could theoretically push the fuel in the bowls out either the jets or the overflow tubes. You could stiull be flooded and not smell fuel because in our engines (unlike a car engine) the exhaust has to go UP the manifold before it goes out. Therefore, the fuel wont come out of the exhaust until you get the boat to fire. Next time it happens, try the wide open throttle trick and see if that works. If it doesnt, then you've pretty much eliminated flooding as the source of your problem.

If thats not it, then all that is left is spark. Like a said earlier, heat is the enemy of the flow of electricity, and any of your ignition components coudl be getting too hot and causing your problem. How old is the coil? Thats the first thing i would suspect. The MSD ignition control systems are pretty tough. They go through a whole lot worse conditions than a boat without problems and i dont think that is likely to be the cause. I'm not sure if a parts store can test a coil or not. If thats not it, then its time to break out the multimeter and start checking the +12v leads to your ignition components.

Good luck.

Cheers,
DKJ