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

[chris young]

"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

Yes it does, the problem is you want as much gas in the bowl as possible without going so high that it starts leaking out the boosters. To my knowledge, no one has posted a float level based on the tilt of the carb, so you have to adjust by trial and error. Since you have to keep removing the bowl to do so, it gets pretty tedious. I'm not so sure that you need to buy a new carb to solve the problem though. In my case, I decided that the carb was designed to run level, so I leveled it, new studs and a wedge spacer (I stacked 2 X 5 deg but you can get 1X10 deg, it was just the easiest way to proceed through my local auto parts shop) There are loads of these boats running around without wedge spacers in them so it's completely doable with just float level I'm sure. I think what ends up happening quite often, is someone decides to refresh the carb, and when they set the float levels they use the Holley recommended float settings, and the problem begins.

[lively]

"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

Yes it does, the problem is you want as much gas in the bowl as possible without going so high that it starts leaking out the boosters. To my knowledge, no one has posted a float level based on the tilt of the carb, so you have to adjust by trial and error. Since you have to keep removing the bowl to do so, it gets pretty tedious. I'm not so sure that you need to buy a new carb to solve the problem though. In my case, I decided that the carb was designed to run level, so I leveled it, new studs and a wedge spacer (I stacked 2 X 5 deg but you can get 1X10 deg, it was just the easiest way to proceed through my local auto parts shop) There are loads of these boats running around without wedge spacers in them so it's completely doable with just float level I'm sure. I think what ends up happening quite often, is someone decides to refresh the carb, and when they set the float levels they use the Holley recommended float settings, and the problem begins. problem with me is the holley was fun and i know it was standard on the supras , i was just never knowledgeable enough to get it quite right , lol i still have it in the shed but the edlebrock marine i put on has had no problems . main issue was i had alot of backfire in the holley with my ign timing and the diaphragm inside the metering block had to change that out a few times lol

[UKandH]

Supras are fitted (as we all know) with 4160 marine Hollies, but there is an option, the 4150, this has 2 metering blocks instead of one and fully adjustable floats that can be adjusted without taking the bowls off. All you do is crack the cover off of the adjuster, turn the screw until fuel trickles out of the hole and refit the plug. Do front and rear bowls in the same fashion when on the water and the carb has perfect set up for marine use where the engine is mounted at an angle. The 4160 cant cope very well with this where as the 4150 can.

Saying that im still running a 4160 thats sweet as a nut after its overhaul a few months ago.. :)

[hockeyGTP]

So I finally got the take the boat back out and try a few things. Saturday after sitting for a few hours in the cove it was slow to turn over but started up. Sunday after sitting a few hours it was slow to turn over again. I held the butterfly flap closed and it started turning over faster and started right up.

[lively]

So I finally got the take the boat back out and try a few things. Saturday after sitting for a few hours in the cove it was slow to turn over but started up. Sunday after sitting a few hours it was slow to turn over again. I held the butterfly flap closed and it started turning over faster and started right up. check you timing , 10 degrees BTDC is a good place i would say 6-10 degrees is the sweet spot .. thats prob your slow turning issue ..

[Salty87]

how old are your battery cables? inefficiencies in the circuit will weaken it.

[Supra_Comp]

Be sure to check the voltage on the positive side of the ignition coil and feel how hot it is. Also check the resistance of the primary coil. What type of dizzy are you running? Generally speaking you will want to see 0.7 Ohms resistance and 9.0 volts while running on the positive side of the coil. If you see anything higher than that, your ballast resistor may be shot or may have wiring issues.

I had this issue on my boat for years and looked right past it assuming that since it ran cold it must be a carb issue.

[hockeyGTP]

Forgive my ignorance, please. I haven't been able to check the boat because after I unhooked the trailer I fractured my ankle. I did notice the last time that where the positive battery wire hooks up at the back of the engine under the gray cover was getting hot and started to smoke some also. I don't know what that part is called, or where the primary coil is, or what a dizzy is. I am hoping to get in the boat Monday and really look at it a lot more.

[Supra_Comp]

No problem man. The part your talking about is probably the starter solenoid, where all the ignition and accessories get the power from.

The ignition coil is the round cylinder that has a single spark plug wire from (usually mounted on the top of the intake manifold by the car or on the front of the engine). That plug wire provides power to the dizzy (aka distributor). On the ignition coil, there is a power wire and another wire on the + terminal that goes to the distributor. If that wire is connected directly to the starter solenoid, it means it is seeing 12 volts and can overheat the coil after running and cause symptoms similar to vapour lock and poor performance/starting. The coil should be hooked up with an inline ballast resistor (white ceramic block which should be under that cover you mentioned) which will reduce the voltage down to 9 volts.

Have a look at this first and take a picture of the wiring hook up.

[Supra_Comp]

Use post 39 for reference.

https://forum.supraboats.com/showthread.php?16488-PCM-351-Vapor-Lock-Issues/page4

[hockeyGTP]

What is the part number for the solenoid between the battery and the starter. I believe I have the issue figured out. The positive battery cable was a complete hack job and very corroded. Got a one piece and went to put it on the solenoid and it (solenoid) fell apart, but looking at the diagram the solenoid that was on there isn't the right one. The one that was on looks almost identical to this one http://shop.advanceautoparts.com/p/carquest-by-bwd-wiring-relay-r3098/18970096-P?searchTerm=battery+relay the one in the link is a little taller. I am either leaning towards the relay is bad or it isn't hooked up correctly. I can short the starter and the battery cable and it keeps starting right up, thus why I believe the orignal problem is solved. With the new relay I turn the key and get nothing, I have the neutral safety wire hooked up and don't see any loose wires to go on the bottom connector of the relay.

[hockeyGTP]

Thought I should update, the solenoid needed a ground wire ran to it, fired right up. The starting issue seems to be fixed with new battery cable ran to the new solenoid also.

I would like to thank everybody for their help with my issue, this forum is great!