1984 Supra 351w - No start after running for a while

[hockeyGTP]

Was almost stranded out on the lake this past weekend. Every time we start it up on the ramp we get no issues. We will run around the lake for a little while and anchor out for a few hours. When we go to start it up to cruise around the lake some more we have been having troubles getting it started. Batteries are showing 13 volts when we go to crank it and it will crank but not "catch" and start. I pulled the cover off the top of the carb (spark arrester?) and saw it was getting fuel when pumping the throttle. We got it in the shade and opened the dog house for 30 minutes and cranked it and it started right up. I did notice that the butterfly flap was all the way open when I took the top off and it wasn't starting. It does have an electric choke. It seems if I turn off the batteries with the switch and turn them back on it will start up. That makes me want to say it may have something to do with the electric choke.

I do not know much about carbs, I do know some about engines in general.

[Jetlink]

Sounds like heat soak is a strong possibility.

[hockeyGTP]

What would be getting heat soaked to cause it? Starter is spinning fine, engine is turning over like normal. When I docked it in the shade the next day at the campsite for an hour it started up fine. I am almost wondering if the electric choke is staying so hot that it isn't being activated while the engine is actually cold. Once it starts everything is fine, idles well and all.

[lestorx]

I have an 85 ts6m and have a similar issue. Also, when I drive for a while, cruising not towing, it sometimes chokes out. When I open the doghouse it is fairly fumey. Not knock you down, but there is some vapor. The blower works fine and I run it all the time. It seem to me like the dose of fresh air is what it needs. I have been thinking about putting another blower in the back, or possibly on the intake hose in the bow to force more fresh air in.

[tripster]

I have 89 comp. Had same problem, bendex solenoid was not releasing from fly wheel, starter would swell and stop the motor. sit for a while would cool and run fine. Then same thing all over.

[lively]

What do you mean ? It will crank but no start ? And did you verify spark ? What about fuel ? 6lbs is best , 3lbs fuel pressure will run . ? What did you check ?

[wotan2525]

Is this a new problem or has it always done this? What kind of carb and has it ever been rebuilt? I bet it's leaking fuel into the cylinders and when you pull the doghouse off and let it sit the fuel evaporates.

[chris young]

I'm with wotan on this one. Mine did the same thing. It's easy to check. After you shut down, pull the spark arrestor and look down the barrels. If any of the barrels are dripping fuel from the boosters, you've found your problem. You can fix it by adjusting the floats, but if your carb is tilted like it is on many of these boats (because the engine is tilted) then adjusting the floats per the holley numbers will leave the front float too high and the rear too low. I gave up on trying to adjust the floats on mine and put in wedge spacers under the carb to level it. In my case the boat was doing this when I bought it, so I have no idea when the problem started. I've never seen anyone post on the subject, but really Supra should have provided float settings based on the inclination of the carb. If this is the case, then the carb will drip until the fuel pressure drops.

One other thing I did for my boat which made a huge difference in easy starts both hot and cold was to run the ballast resistor bypass wire from the starter solenoid to the coil, you need an external solenoid for this that has a second relay in it for this express purpose. Now the boat starts great both hot and cold.

I would doubt that it is a choke issue. If the motor is hot enough to keep the choke open with the key off then it shouldn't need any choke to start. Also one quick pump of the throttle would rule this out, as that little squirt of fuel will be plenty.

Good luck, keep us posted

[Terrance Estenson]

I have had this problem after dumping a lot of money in the boat last summer.
New Electronic ignition,new coil, new double batteries,and complete Holley Carb rebuild.
I am interested in the wedge to keep the carb level.
The carb is dumping gas after it gets warm.
It then floods and becomes hard to start.
The carb specialist claimed it must be dirty gas tank.
I have three filters inline with the electric fuel pump.
I have 4 PSI at carb.
I think this is a common problem with the PCM 351 after reading many Blogs.

[lively]

I have had this problem after dumping a lot of money in the boat last summer.
New Electronic ignition,new coil, new double batteries,and complete Holley Carb rebuild.
I am interested in the wedge to keep the carb level.
The carb is dumping gas after it gets warm.
It then floods and becomes hard to start.
The carb specialist claimed it must be dirty gas tank.
I have three filters inline with the electric fuel pump.
I have 4 PSI at carb.
I think this is a common problem with the PCM 351 after reading many Blogs.

the Holley 4bbl has a float level that you must adjust so that the boosters will not leak into intake , i switched to a edlebrock and it starts up instantly